Partially revert "video: fbdev: amba-clcd: Retire elder CLCD driver"

Also partially revert the follow-up change "drm: pl111: Absorb the
external register header".

This reverts the parts of commits
7e4e589db76a3cf4c1f534eb5a09cc6422766b93 and
0fb8125635e8eb5483fb095f98dcf0651206a7b8 that touch paths outside
of drivers/gpu/drm/pl111.

The fbdev driver is used by Android's FVP configuration. Using the
DRM driver together with DRM's fbdev emulation results in a failure
to boot Android. The root cause is that Android's generic fbdev
userspace driver relies on the ability to set the pixel format via
FBIOPUT_VSCREENINFO, which is not supported by fbdev emulation.

There have been other less critical behavioral differences identified
between the fbdev driver and the DRM driver with fbdev emulation. The
DRM driver exposes different values for the panel's width, height and
refresh rate, and the DRM driver fails a FBIOPUT_VSCREENINFO syscall
with yres_virtual greater than the maximum supported value instead
of letting the syscall succeed and setting yres_virtual based on yres.

Signed-off-by: Peter Collingbourne <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

MAINTAINERS

···
 F:	drivers/amba/
 F:	include/linux/amba/bus.h
 
+ARM PRIMECELL CLCD PL110 DRIVER
+M:	Russell King <[e-mail]>
+S:	Odd Fixes
+F:	drivers/video/fbdev/amba-clcd.*
+
 ARM PRIMECELL KMI PL050 DRIVER
 M:	Russell King <[e-mail]>
 S:	Odd Fixes

drivers/video/fbdev/Kconfig

···
 	help
 	  Support the Permedia2 FIFO disconnect feature.
 
+config FB_ARMCLCD
+	tristate "ARM PrimeCell PL110 support"
+	depends on ARM || ARM64 || COMPILE_TEST
+	depends on FB && ARM_AMBA && HAS_IOMEM
+	select FB_CFB_FILLRECT
+	select FB_CFB_COPYAREA
+	select FB_CFB_IMAGEBLIT
+	select FB_MODE_HELPERS if OF
+	select VIDEOMODE_HELPERS if OF
+	select BACKLIGHT_CLASS_DEVICE if OF
+	help
+	  This framebuffer device driver is for the ARM PrimeCell PL110
+	  Colour LCD controller.  ARM PrimeCells provide the building
+	  blocks for System on a Chip devices.
+
+	  If you want to compile this as a module (=code which can be
+	  inserted into and removed from the running kernel), say M
+	  here and read <file:Documentation/kbuild/modules.rst>.  The module
+	  will be called amba-clcd.
+
 config FB_ACORN
 	bool "Acorn VIDC support"
 	depends on (FB = y) && ARM && ARCH_ACORN

drivers/video/fbdev/Makefile

···
 obj-$(CONFIG_FB_ATMEL)		  += atmel_lcdfb.o
 obj-$(CONFIG_FB_PVR2)             += pvr2fb.o
 obj-$(CONFIG_FB_VOODOO1)          += sstfb.o
+obj-$(CONFIG_FB_ARMCLCD)	  += amba-clcd.o
 obj-$(CONFIG_FB_GOLDFISH)         += goldfishfb.o
 obj-$(CONFIG_FB_68328)            += 68328fb.o
 obj-$(CONFIG_FB_GBE)              += gbefb.o

drivers/video/fbdev/amba-clcd.c

···
+/*
+ *  linux/drivers/video/amba-clcd.c
+ *
+ * Copyright (C) 2001 ARM Limited, by David A Rusling
+ * Updated to 2.5, Deep Blue Solutions Ltd.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ *
+ *  ARM PrimeCell PL110 Color LCD Controller
+ */
+#include <linux/amba/bus.h>
+#include <linux/amba/clcd.h>
+#include <linux/backlight.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_graph.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <video/display_timing.h>
+#include <video/of_display_timing.h>
+#include <video/videomode.h>
+
+#define to_clcd(info)	container_of(info, struct clcd_fb, fb)
+
+/* This is limited to 16 characters when displayed by X startup */
+static const char *clcd_name = "CLCD FB";
+
+/*
+ * Unfortunately, the enable/disable functions may be called either from
+ * process or IRQ context, and we _need_ to delay.  This is _not_ good.
+ */
+static inline void clcdfb_sleep(unsigned int ms)
+{
+	if (in_atomic()) {
+		mdelay(ms);
+	} else {
+		msleep(ms);
+	}
+}
+
+static inline void clcdfb_set_start(struct clcd_fb *fb)
+{
+	unsigned long ustart = fb->fb.fix.smem_start;
+	unsigned long lstart;
+
+	ustart += fb->fb.var.yoffset * fb->fb.fix.line_length;
+	lstart = ustart + fb->fb.var.yres * fb->fb.fix.line_length / 2;
+
+	writel(ustart, fb->regs + CLCD_UBAS);
+	writel(lstart, fb->regs + CLCD_LBAS);
+}
+
+static void clcdfb_disable(struct clcd_fb *fb)
+{
+	u32 val;
+
+	if (fb->board->disable)
+		fb->board->disable(fb);
+
+	if (fb->panel->backlight) {
+		fb->panel->backlight->props.power = FB_BLANK_POWERDOWN;
+		backlight_update_status(fb->panel->backlight);
+	}
+
+	val = readl(fb->regs + fb->off_cntl);
+	if (val & CNTL_LCDPWR) {
+		val &= ~CNTL_LCDPWR;
+		writel(val, fb->regs + fb->off_cntl);
+
+		clcdfb_sleep(20);
+	}
+	if (val & CNTL_LCDEN) {
+		val &= ~CNTL_LCDEN;
+		writel(val, fb->regs + fb->off_cntl);
+	}
+
+	/*
+	 * Disable CLCD clock source.
+	 */
+	if (fb->clk_enabled) {
+		fb->clk_enabled = false;
+		clk_disable(fb->clk);
+	}
+}
+
+static void clcdfb_enable(struct clcd_fb *fb, u32 cntl)
+{
+	/*
+	 * Enable the CLCD clock source.
+	 */
+	if (!fb->clk_enabled) {
+		fb->clk_enabled = true;
+		clk_enable(fb->clk);
+	}
+
+	/*
+	 * Bring up by first enabling..
+	 */
+	cntl |= CNTL_LCDEN;
+	writel(cntl, fb->regs + fb->off_cntl);
+
+	clcdfb_sleep(20);
+
+	/*
+	 * and now apply power.
+	 */
+	cntl |= CNTL_LCDPWR;
+	writel(cntl, fb->regs + fb->off_cntl);
+
+	/*
+	 * Turn on backlight
+	 */
+	if (fb->panel->backlight) {
+		fb->panel->backlight->props.power = FB_BLANK_UNBLANK;
+		backlight_update_status(fb->panel->backlight);
+	}
+
+	/*
+	 * finally, enable the interface.
+	 */
+	if (fb->board->enable)
+		fb->board->enable(fb);
+}
+
+static int
+clcdfb_set_bitfields(struct clcd_fb *fb, struct fb_var_screeninfo *var)
+{
+	u32 caps;
+	int ret = 0;
+
+	if (fb->panel->caps && fb->board->caps)
+		caps = fb->panel->caps & fb->board->caps;
+	else {
+		/* Old way of specifying what can be used */
+		caps = fb->panel->cntl & CNTL_BGR ?
+			CLCD_CAP_BGR : CLCD_CAP_RGB;
+		/* But mask out 444 modes as they weren't supported */
+		caps &= ~CLCD_CAP_444;
+	}
+
+	/* Only TFT panels can do RGB888/BGR888 */
+	if (!(fb->panel->cntl & CNTL_LCDTFT))
+		caps &= ~CLCD_CAP_888;
+
+	memset(&var->transp, 0, sizeof(var->transp));
+
+	var->red.msb_right = 0;
+	var->green.msb_right = 0;
+	var->blue.msb_right = 0;
+
+	switch (var->bits_per_pixel) {
+	case 1:
+	case 2:
+	case 4:
+	case 8:
+		/* If we can't do 5551, reject */
+		caps &= CLCD_CAP_5551;
+		if (!caps) {
+			ret = -EINVAL;
+			break;
+		}
+
+		var->red.length		= var->bits_per_pixel;
+		var->red.offset		= 0;
+		var->green.length	= var->bits_per_pixel;
+		var->green.offset	= 0;
+		var->blue.length	= var->bits_per_pixel;
+		var->blue.offset	= 0;
+		break;
+
+	case 16:
+		/* If we can't do 444, 5551 or 565, reject */
+		if (!(caps & (CLCD_CAP_444 | CLCD_CAP_5551 | CLCD_CAP_565))) {
+			ret = -EINVAL;
+			break;
+		}
+
+		/*
+		 * Green length can be 4, 5 or 6 depending whether
+		 * we're operating in 444, 5551 or 565 mode.
+		 */
+		if (var->green.length == 4 && caps & CLCD_CAP_444)
+			caps &= CLCD_CAP_444;
+		if (var->green.length == 5 && caps & CLCD_CAP_5551)
+			caps &= CLCD_CAP_5551;
+		else if (var->green.length == 6 && caps & CLCD_CAP_565)
+			caps &= CLCD_CAP_565;
+		else {
+			/*
+			 * PL110 officially only supports RGB555,
+			 * but may be wired up to allow RGB565.
+			 */
+			if (caps & CLCD_CAP_565) {
+				var->green.length = 6;
+				caps &= CLCD_CAP_565;
+			} else if (caps & CLCD_CAP_5551) {
+				var->green.length = 5;
+				caps &= CLCD_CAP_5551;
+			} else {
+				var->green.length = 4;
+				caps &= CLCD_CAP_444;
+			}
+		}
+
+		if (var->green.length >= 5) {
+			var->red.length = 5;
+			var->blue.length = 5;
+		} else {
+			var->red.length = 4;
+			var->blue.length = 4;
+		}
+		break;
+	case 32:
+		/* If we can't do 888, reject */
+		caps &= CLCD_CAP_888;
+		if (!caps) {
+			ret = -EINVAL;
+			break;
+		}
+
+		var->red.length = 8;
+		var->green.length = 8;
+		var->blue.length = 8;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	/*
+	 * >= 16bpp displays have separate colour component bitfields
+	 * encoded in the pixel data.  Calculate their position from
+	 * the bitfield length defined above.
+	 */
+	if (ret == 0 && var->bits_per_pixel >= 16) {
+		bool bgr, rgb;
+
+		bgr = caps & CLCD_CAP_BGR && var->blue.offset == 0;
+		rgb = caps & CLCD_CAP_RGB && var->red.offset == 0;
+
+		if (!bgr && !rgb)
+			/*
+			 * The requested format was not possible, try just
+			 * our capabilities.  One of BGR or RGB must be
+			 * supported.
+			 */
+			bgr = caps & CLCD_CAP_BGR;
+
+		if (bgr) {
+			var->blue.offset = 0;
+			var->green.offset = var->blue.offset + var->blue.length;
+			var->red.offset = var->green.offset + var->green.length;
+		} else {
+			var->red.offset = 0;
+			var->green.offset = var->red.offset + var->red.length;
+			var->blue.offset = var->green.offset + var->green.length;
+		}
+	}
+
+	return ret;
+}
+
+static int clcdfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	struct clcd_fb *fb = to_clcd(info);
+	int ret = -EINVAL;
+
+	if (fb->board->check)
+		ret = fb->board->check(fb, var);
+
+	if (ret == 0 &&
+	    var->xres_virtual * var->bits_per_pixel / 8 *
+	    var->yres_virtual > fb->fb.fix.smem_len)
+		ret = -EINVAL;
+
+	if (ret == 0)
+		ret = clcdfb_set_bitfields(fb, var);
+
+	return ret;
+}
+
+static int clcdfb_set_par(struct fb_info *info)
+{
+	struct clcd_fb *fb = to_clcd(info);
+	struct clcd_regs regs;
+
+	fb->fb.fix.line_length = fb->fb.var.xres_virtual *
+				 fb->fb.var.bits_per_pixel / 8;
+
+	if (fb->fb.var.bits_per_pixel <= 8)
+		fb->fb.fix.visual = FB_VISUAL_PSEUDOCOLOR;
+	else
+		fb->fb.fix.visual = FB_VISUAL_TRUECOLOR;
+
+	fb->board->decode(fb, &regs);
+
+	clcdfb_disable(fb);
+
+	writel(regs.tim0, fb->regs + CLCD_TIM0);
+	writel(regs.tim1, fb->regs + CLCD_TIM1);
+	writel(regs.tim2, fb->regs + CLCD_TIM2);
+	writel(regs.tim3, fb->regs + CLCD_TIM3);
+
+	clcdfb_set_start(fb);
+
+	clk_set_rate(fb->clk, (1000000000 / regs.pixclock) * 1000);
+
+	fb->clcd_cntl = regs.cntl;
+
+	clcdfb_enable(fb, regs.cntl);
+
+#ifdef DEBUG
+	printk(KERN_INFO
+	       "CLCD: Registers set to\n"
+	       "  %08x %08x %08x %08x\n"
+	       "  %08x %08x %08x %08x\n",
+		readl(fb->regs + CLCD_TIM0), readl(fb->regs + CLCD_TIM1),
+		readl(fb->regs + CLCD_TIM2), readl(fb->regs + CLCD_TIM3),
+		readl(fb->regs + CLCD_UBAS), readl(fb->regs + CLCD_LBAS),
+		readl(fb->regs + fb->off_ienb), readl(fb->regs + fb->off_cntl));
+#endif
+
+	return 0;
+}
+
+static inline u32 convert_bitfield(int val, struct fb_bitfield *bf)
+{
+	unsigned int mask = (1 << bf->length) - 1;
+
+	return (val >> (16 - bf->length) & mask) << bf->offset;
+}
+
+/*
+ *  Set a single color register. The values supplied have a 16 bit
+ *  magnitude.  Return != 0 for invalid regno.
+ */
+static int
+clcdfb_setcolreg(unsigned int regno, unsigned int red, unsigned int green,
+		 unsigned int blue, unsigned int transp, struct fb_info *info)
+{
+	struct clcd_fb *fb = to_clcd(info);
+
+	if (regno < 16)
+		fb->cmap[regno] = convert_bitfield(transp, &fb->fb.var.transp) |
+				  convert_bitfield(blue, &fb->fb.var.blue) |
+				  convert_bitfield(green, &fb->fb.var.green) |
+				  convert_bitfield(red, &fb->fb.var.red);
+
+	if (fb->fb.fix.visual == FB_VISUAL_PSEUDOCOLOR && regno < 256) {
+		int hw_reg = CLCD_PALETTE + ((regno * 2) & ~3);
+		u32 val, mask, newval;
+
+		newval  = (red >> 11)  & 0x001f;
+		newval |= (green >> 6) & 0x03e0;
+		newval |= (blue >> 1)  & 0x7c00;
+
+		/*
+		 * 3.2.11: if we're configured for big endian
+		 * byte order, the palette entries are swapped.
+		 */
+		if (fb->clcd_cntl & CNTL_BEBO)
+			regno ^= 1;
+
+		if (regno & 1) {
+			newval <<= 16;
+			mask = 0x0000ffff;
+		} else {
+			mask = 0xffff0000;
+		}
+
+		val = readl(fb->regs + hw_reg) & mask;
+		writel(val | newval, fb->regs + hw_reg);
+	}
+
+	return regno > 255;
+}
+
+/*
+ *  Blank the screen if blank_mode != 0, else unblank. If blank == NULL
+ *  then the caller blanks by setting the CLUT (Color Look Up Table) to all
+ *  black. Return 0 if blanking succeeded, != 0 if un-/blanking failed due
+ *  to e.g. a video mode which doesn't support it. Implements VESA suspend
+ *  and powerdown modes on hardware that supports disabling hsync/vsync:
+ *    blank_mode == 2: suspend vsync
+ *    blank_mode == 3: suspend hsync
+ *    blank_mode == 4: powerdown
+ */
+static int clcdfb_blank(int blank_mode, struct fb_info *info)
+{
+	struct clcd_fb *fb = to_clcd(info);
+
+	if (blank_mode != 0) {
+		clcdfb_disable(fb);
+	} else {
+		clcdfb_enable(fb, fb->clcd_cntl);
+	}
+	return 0;
+}
+
+static int clcdfb_mmap(struct fb_info *info,
+		       struct vm_area_struct *vma)
+{
+	struct clcd_fb *fb = to_clcd(info);
+	unsigned long len, off = vma->vm_pgoff << PAGE_SHIFT;
+	int ret = -EINVAL;
+
+	len = info->fix.smem_len;
+
+	if (off <= len && vma->vm_end - vma->vm_start <= len - off &&
+	    fb->board->mmap)
+		ret = fb->board->mmap(fb, vma);
+
+	return ret;
+}
+
+static const struct fb_ops clcdfb_ops = {
+	.owner		= THIS_MODULE,
+	.fb_check_var	= clcdfb_check_var,
+	.fb_set_par	= clcdfb_set_par,
+	.fb_setcolreg	= clcdfb_setcolreg,
+	.fb_blank	= clcdfb_blank,
+	.fb_fillrect	= cfb_fillrect,
+	.fb_copyarea	= cfb_copyarea,
+	.fb_imageblit	= cfb_imageblit,
+	.fb_mmap	= clcdfb_mmap,
+};
+
+static int clcdfb_register(struct clcd_fb *fb)
+{
+	int ret;
+
+	/*
+	 * ARM PL111 always has IENB at 0x1c; it's only PL110
+	 * which is reversed on some platforms.
+	 */
+	if (amba_manf(fb->dev) == 0x41 && amba_part(fb->dev) == 0x111) {
+		fb->off_ienb = CLCD_PL111_IENB;
+		fb->off_cntl = CLCD_PL111_CNTL;
+	} else {
+		fb->off_ienb = CLCD_PL110_IENB;
+		fb->off_cntl = CLCD_PL110_CNTL;
+	}
+
+	fb->clk = clk_get(&fb->dev->dev, NULL);
+	if (IS_ERR(fb->clk)) {
+		ret = PTR_ERR(fb->clk);
+		goto out;
+	}
+
+	ret = clk_prepare(fb->clk);
+	if (ret)
+		goto free_clk;
+
+	fb->fb.device		= &fb->dev->dev;
+
+	fb->fb.fix.mmio_start	= fb->dev->res.start;
+	fb->fb.fix.mmio_len	= resource_size(&fb->dev->res);
+
+	fb->regs = ioremap(fb->fb.fix.mmio_start, fb->fb.fix.mmio_len);
+	if (!fb->regs) {
+		printk(KERN_ERR "CLCD: unable to remap registers\n");
+		ret = -ENOMEM;
+		goto clk_unprep;
+	}
+
+	fb->fb.fbops		= &clcdfb_ops;
+	fb->fb.flags		= FBINFO_FLAG_DEFAULT;
+	fb->fb.pseudo_palette	= fb->cmap;
+
+	strncpy(fb->fb.fix.id, clcd_name, sizeof(fb->fb.fix.id));
+	fb->fb.fix.type		= FB_TYPE_PACKED_PIXELS;
+	fb->fb.fix.type_aux	= 0;
+	fb->fb.fix.xpanstep	= 0;
+	fb->fb.fix.ypanstep	= 0;
+	fb->fb.fix.ywrapstep	= 0;
+	fb->fb.fix.accel	= FB_ACCEL_NONE;
+
+	fb->fb.var.xres		= fb->panel->mode.xres;
+	fb->fb.var.yres		= fb->panel->mode.yres;
+	fb->fb.var.xres_virtual	= fb->panel->mode.xres;
+	fb->fb.var.yres_virtual	= fb->panel->mode.yres;
+	fb->fb.var.bits_per_pixel = fb->panel->bpp;
+	fb->fb.var.grayscale	= fb->panel->grayscale;
+	fb->fb.var.pixclock	= fb->panel->mode.pixclock;
+	fb->fb.var.left_margin	= fb->panel->mode.left_margin;
+	fb->fb.var.right_margin	= fb->panel->mode.right_margin;
+	fb->fb.var.upper_margin	= fb->panel->mode.upper_margin;
+	fb->fb.var.lower_margin	= fb->panel->mode.lower_margin;
+	fb->fb.var.hsync_len	= fb->panel->mode.hsync_len;
+	fb->fb.var.vsync_len	= fb->panel->mode.vsync_len;
+	fb->fb.var.sync		= fb->panel->mode.sync;
+	fb->fb.var.vmode	= fb->panel->mode.vmode;
+	fb->fb.var.activate	= FB_ACTIVATE_NOW;
+	fb->fb.var.nonstd	= 0;
+	fb->fb.var.height	= fb->panel->height;
+	fb->fb.var.width	= fb->panel->width;
+	fb->fb.var.accel_flags	= 0;
+
+	fb->fb.monspecs.hfmin	= 0;
+	fb->fb.monspecs.hfmax   = 100000;
+	fb->fb.monspecs.vfmin	= 0;
+	fb->fb.monspecs.vfmax	= 400;
+	fb->fb.monspecs.dclkmin = 1000000;
+	fb->fb.monspecs.dclkmax	= 100000000;
+
+	/*
+	 * Make sure that the bitfields are set appropriately.
+	 */
+	clcdfb_set_bitfields(fb, &fb->fb.var);
+
+	/*
+	 * Allocate colourmap.
+	 */
+	ret = fb_alloc_cmap(&fb->fb.cmap, 256, 0);
+	if (ret)
+		goto unmap;
+
+	/*
+	 * Ensure interrupts are disabled.
+	 */
+	writel(0, fb->regs + fb->off_ienb);
+
+	fb_set_var(&fb->fb, &fb->fb.var);
+
+	dev_info(&fb->dev->dev, "%s hardware, %s display\n",
+	         fb->board->name, fb->panel->mode.name);
+
+	ret = register_framebuffer(&fb->fb);
+	if (ret == 0)
+		goto out;
+
+	printk(KERN_ERR "CLCD: cannot register framebuffer (%d)\n", ret);
+
+	fb_dealloc_cmap(&fb->fb.cmap);
+ unmap:
+	iounmap(fb->regs);
+ clk_unprep:
+	clk_unprepare(fb->clk);
+ free_clk:
+	clk_put(fb->clk);
+ out:
+	return ret;
+}
+
+#ifdef CONFIG_OF
+static int clcdfb_of_get_dpi_panel_mode(struct device_node *node,
+		struct clcd_panel *clcd_panel)
+{
+	int err;
+	struct display_timing timing;
+	struct videomode video;
+
+	err = of_get_display_timing(node, "panel-timing", &timing);
+	if (err) {
+		pr_err("%pOF: problems parsing panel-timing (%d)\n", node, err);
+		return err;
+	}
+
+	videomode_from_timing(&timing, &video);
+
+	err = fb_videomode_from_videomode(&video, &clcd_panel->mode);
+	if (err)
+		return err;
+
+	/* Set up some inversion flags */
+	if (timing.flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
+		clcd_panel->tim2 |= TIM2_IPC;
+	else if (!(timing.flags & DISPLAY_FLAGS_PIXDATA_POSEDGE))
+		/*
+		 * To preserve backwards compatibility, the IPC (inverted
+		 * pixel clock) flag needs to be set on any display that
+		 * doesn't explicitly specify that the pixel clock is
+		 * active on the negative or positive edge.
+		 */
+		clcd_panel->tim2 |= TIM2_IPC;
+
+	if (timing.flags & DISPLAY_FLAGS_HSYNC_LOW)
+		clcd_panel->tim2 |= TIM2_IHS;
+
+	if (timing.flags & DISPLAY_FLAGS_VSYNC_LOW)
+		clcd_panel->tim2 |= TIM2_IVS;
+
+	if (timing.flags & DISPLAY_FLAGS_DE_LOW)
+		clcd_panel->tim2 |= TIM2_IOE;
+
+	return 0;
+}
+
+static int clcdfb_snprintf_mode(char *buf, int size, struct fb_videomode *mode)
+{
+	return snprintf(buf, size, "%ux%u@%u", mode->xres, mode->yres,
+			mode->refresh);
+}
+
+static int clcdfb_of_get_backlight(struct device *dev,
+				   struct clcd_panel *clcd_panel)
+{
+	struct backlight_device *backlight;
+
+	/* Look up the optional backlight device */
+	backlight = devm_of_find_backlight(dev);
+	if (IS_ERR(backlight))
+		return PTR_ERR(backlight);
+
+	clcd_panel->backlight = backlight;
+	return 0;
+}
+
+static int clcdfb_of_get_mode(struct device *dev, struct device_node *panel,
+			      struct clcd_panel *clcd_panel)
+{
+	int err;
+	struct fb_videomode *mode;
+	char *name;
+	int len;
+
+	/* Only directly connected DPI panels supported for now */
+	if (of_device_is_compatible(panel, "panel-dpi"))
+		err = clcdfb_of_get_dpi_panel_mode(panel, clcd_panel);
+	else
+		err = -ENOENT;
+	if (err)
+		return err;
+	mode = &clcd_panel->mode;
+
+	len = clcdfb_snprintf_mode(NULL, 0, mode);
+	name = devm_kzalloc(dev, len + 1, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+
+	clcdfb_snprintf_mode(name, len + 1, mode);
+	mode->name = name;
+
+	return 0;
+}
+
+static int clcdfb_of_init_tft_panel(struct clcd_fb *fb, u32 r0, u32 g0, u32 b0)
+{
+	static struct {
+		unsigned int part;
+		u32 r0, g0, b0;
+		u32 caps;
+	} panels[] = {
+		{ 0x110, 1,  7, 13, CLCD_CAP_5551 },
+		{ 0x110, 0,  8, 16, CLCD_CAP_888 },
+		{ 0x110, 16, 8, 0,  CLCD_CAP_888 },
+		{ 0x111, 4, 14, 20, CLCD_CAP_444 },
+		{ 0x111, 3, 11, 19, CLCD_CAP_444 | CLCD_CAP_5551 },
+		{ 0x111, 3, 10, 19, CLCD_CAP_444 | CLCD_CAP_5551 |
+				    CLCD_CAP_565 },
+		{ 0x111, 0,  8, 16, CLCD_CAP_444 | CLCD_CAP_5551 |
+				    CLCD_CAP_565 | CLCD_CAP_888 },
+	};
+	int i;
+
+	/* Bypass pixel clock divider */
+	fb->panel->tim2 |= TIM2_BCD;
+
+	/* TFT display, vert. comp. interrupt at the start of the back porch */
+	fb->panel->cntl |= CNTL_LCDTFT | CNTL_LCDVCOMP(1);
+
+	fb->panel->caps = 0;
+
+	/* Match the setup with known variants */
+	for (i = 0; i < ARRAY_SIZE(panels) && !fb->panel->caps; i++) {
+		if (amba_part(fb->dev) != panels[i].part)
+			continue;
+		if (g0 != panels[i].g0)
+			continue;
+		if (r0 == panels[i].r0 && b0 == panels[i].b0)
+			fb->panel->caps = panels[i].caps;
+	}
+
+	/*
+	 * If we actually physically connected the R lines to B and
+	 * vice versa
+	 */
+	if (r0 != 0 && b0 == 0)
+		fb->panel->bgr_connection = true;
+
+	return fb->panel->caps ? 0 : -EINVAL;
+}
+
+static int clcdfb_of_init_display(struct clcd_fb *fb)
+{
+	struct device_node *endpoint, *panel;
+	int err;
+	unsigned int bpp;
+	u32 max_bandwidth;
+	u32 tft_r0b0g0[3];
+
+	fb->panel = devm_kzalloc(&fb->dev->dev, sizeof(*fb->panel), GFP_KERNEL);
+	if (!fb->panel)
+		return -ENOMEM;
+
+	/*
+	 * Fetch the panel endpoint.
+	 */
+	endpoint = of_graph_get_next_endpoint(fb->dev->dev.of_node, NULL);
+	if (!endpoint)
+		return -ENODEV;
+
+	panel = of_graph_get_remote_port_parent(endpoint);
+	if (!panel)
+		return -ENODEV;
+
+	err = clcdfb_of_get_backlight(&fb->dev->dev, fb->panel);
+	if (err)
+		return err;
+
+	err = clcdfb_of_get_mode(&fb->dev->dev, panel, fb->panel);
+	if (err)
+		return err;
+
+	err = of_property_read_u32(fb->dev->dev.of_node, "max-memory-bandwidth",
+			&max_bandwidth);
+	if (!err) {
+		/*
+		 * max_bandwidth is in bytes per second and pixclock in
+		 * pico-seconds, so the maximum allowed bits per pixel is
+		 *   8 * max_bandwidth / (PICOS2KHZ(pixclock) * 1000)
+		 * Rearrange this calculation to avoid overflow and then ensure
+		 * result is a valid format.
+		 */
+		bpp = max_bandwidth / (1000 / 8)
+			/ PICOS2KHZ(fb->panel->mode.pixclock);
+		bpp = rounddown_pow_of_two(bpp);
+		if (bpp > 32)
+			bpp = 32;
+	} else
+		bpp = 32;
+	fb->panel->bpp = bpp;
+
+#ifdef CONFIG_CPU_BIG_ENDIAN
+	fb->panel->cntl |= CNTL_BEBO;
+#endif
+	fb->panel->width = -1;
+	fb->panel->height = -1;
+
+	if (of_property_read_u32_array(endpoint,
+			"arm,pl11x,tft-r0g0b0-pads",
+			tft_r0b0g0, ARRAY_SIZE(tft_r0b0g0)) != 0)
+		return -ENOENT;
+
+	return clcdfb_of_init_tft_panel(fb, tft_r0b0g0[0],
+					tft_r0b0g0[1],  tft_r0b0g0[2]);
+}
+
+static int clcdfb_of_vram_setup(struct clcd_fb *fb)
+{
+	int err;
+	struct device_node *memory;
+	u64 size;
+
+	err = clcdfb_of_init_display(fb);
+	if (err)
+		return err;
+
+	memory = of_parse_phandle(fb->dev->dev.of_node, "memory-region", 0);
+	if (!memory)
+		return -ENODEV;
+
+	fb->fb.screen_base = of_iomap(memory, 0);
+	if (!fb->fb.screen_base)
+		return -ENOMEM;
+
+	fb->fb.fix.smem_start = of_translate_address(memory,
+			of_get_address(memory, 0, &size, NULL));
+	fb->fb.fix.smem_len = size;
+
+	return 0;
+}
+
+static int clcdfb_of_vram_mmap(struct clcd_fb *fb, struct vm_area_struct *vma)
+{
+	unsigned long off, user_size, kernel_size;
+
+
+	off = vma->vm_pgoff << PAGE_SHIFT;
+	user_size = vma->vm_end - vma->vm_start;
+	kernel_size = fb->fb.fix.smem_len;
+
+	if (off >= kernel_size || user_size > (kernel_size - off))
+		return -ENXIO;
+
+	return remap_pfn_range(vma, vma->vm_start,
+			__phys_to_pfn(fb->fb.fix.smem_start) + vma->vm_pgoff,
+			user_size,
+			pgprot_writecombine(vma->vm_page_prot));
+}
+
+static void clcdfb_of_vram_remove(struct clcd_fb *fb)
+{
+	iounmap(fb->fb.screen_base);
+}
+
+static int clcdfb_of_dma_setup(struct clcd_fb *fb)
+{
+	unsigned long framesize;
+	dma_addr_t dma;
+	int err;
+
+	err = clcdfb_of_init_display(fb);
+	if (err)
+		return err;
+
+	framesize = PAGE_ALIGN(fb->panel->mode.xres * fb->panel->mode.yres *
+			fb->panel->bpp / 8);
+	fb->fb.screen_base = dma_alloc_coherent(&fb->dev->dev, framesize,
+			&dma, GFP_KERNEL);
+	if (!fb->fb.screen_base)
+		return -ENOMEM;
+
+	fb->fb.fix.smem_start = dma;
+	fb->fb.fix.smem_len = framesize;
+
+	return 0;
+}
+
+static int clcdfb_of_dma_mmap(struct clcd_fb *fb, struct vm_area_struct *vma)
+{
+	return dma_mmap_wc(&fb->dev->dev, vma, fb->fb.screen_base,
+			   fb->fb.fix.smem_start, fb->fb.fix.smem_len);
+}
+
+static void clcdfb_of_dma_remove(struct clcd_fb *fb)
+{
+	dma_free_coherent(&fb->dev->dev, fb->fb.fix.smem_len,
+			fb->fb.screen_base, fb->fb.fix.smem_start);
+}
+
+static struct clcd_board *clcdfb_of_get_board(struct amba_device *dev)
+{
+	struct clcd_board *board = devm_kzalloc(&dev->dev, sizeof(*board),
+			GFP_KERNEL);
+	struct device_node *node = dev->dev.of_node;
+
+	if (!board)
+		return NULL;
+
+	board->name = of_node_full_name(node);
+	board->caps = CLCD_CAP_ALL;
+	board->check = clcdfb_check;
+	board->decode = clcdfb_decode;
+	if (of_find_property(node, "memory-region", NULL)) {
+		board->setup = clcdfb_of_vram_setup;
+		board->mmap = clcdfb_of_vram_mmap;
+		board->remove = clcdfb_of_vram_remove;
+	} else {
+		board->setup = clcdfb_of_dma_setup;
+		board->mmap = clcdfb_of_dma_mmap;
+		board->remove = clcdfb_of_dma_remove;
+	}
+
+	return board;
+}
+#else
+static struct clcd_board *clcdfb_of_get_board(struct amba_device *dev)
+{
+	return NULL;
+}
+#endif
+
+static int clcdfb_probe(struct amba_device *dev, const struct amba_id *id)
+{
+	struct clcd_board *board = dev_get_platdata(&dev->dev);
+	struct clcd_fb *fb;
+	int ret;
+
+	if (!board)
+		board = clcdfb_of_get_board(dev);
+
+	if (!board)
+		return -EINVAL;
+
+	ret = dma_set_mask_and_coherent(&dev->dev, DMA_BIT_MASK(32));
+	if (ret)
+		goto out;
+
+	ret = amba_request_regions(dev, NULL);
+	if (ret) {
+		printk(KERN_ERR "CLCD: unable to reserve regs region\n");
+		goto out;
+	}
+
+	fb = kzalloc(sizeof(*fb), GFP_KERNEL);
+	if (!fb) {
+		ret = -ENOMEM;
+		goto free_region;
+	}
+
+	fb->dev = dev;
+	fb->board = board;
+
+	dev_info(&fb->dev->dev, "PL%03x designer %02x rev%u at 0x%08llx\n",
+		amba_part(dev), amba_manf(dev), amba_rev(dev),
+		(unsigned long long)dev->res.start);
+
+	ret = fb->board->setup(fb);
+	if (ret)
+		goto free_fb;
+
+	ret = clcdfb_register(fb);
+	if (ret == 0) {
+		amba_set_drvdata(dev, fb);
+		goto out;
+	}
+
+	fb->board->remove(fb);
+ free_fb:
+	kfree(fb);
+ free_region:
+	amba_release_regions(dev);
+ out:
+	return ret;
+}
+
+static int clcdfb_remove(struct amba_device *dev)
+{
+	struct clcd_fb *fb = amba_get_drvdata(dev);
+
+	clcdfb_disable(fb);
+	unregister_framebuffer(&fb->fb);
+	if (fb->fb.cmap.len)
+		fb_dealloc_cmap(&fb->fb.cmap);
+	iounmap(fb->regs);
+	clk_unprepare(fb->clk);
+	clk_put(fb->clk);
+
+	fb->board->remove(fb);
+
+	kfree(fb);
+
+	amba_release_regions(dev);
+
+	return 0;
+}
+
+static const struct amba_id clcdfb_id_table[] = {
+	{
+		.id	= 0x00041110,
+		.mask	= 0x000ffffe,
+	},
+	{ 0, 0 },
+};
+
+MODULE_DEVICE_TABLE(amba, clcdfb_id_table);
+
+static struct amba_driver clcd_driver = {
+	.drv 		= {
+		.name	= "clcd-pl11x",
+	},
+	.probe		= clcdfb_probe,
+	.remove		= clcdfb_remove,
+	.id_table	= clcdfb_id_table,
+};
+
+static int __init amba_clcdfb_init(void)
+{
+	if (fb_get_options("ambafb", NULL))
+		return -ENODEV;
+
+	return amba_driver_register(&clcd_driver);
+}
+
+module_init(amba_clcdfb_init);
+
+static void __exit amba_clcdfb_exit(void)
+{
+	amba_driver_unregister(&clcd_driver);
+}
+
+module_exit(amba_clcdfb_exit);
+
+MODULE_DESCRIPTION("ARM PrimeCell PL110 CLCD core driver");
+MODULE_LICENSE("GPL");

include/linux/amba/clcd-regs.h

···
+/*
+ * David A Rusling
+ *
+ * Copyright (C) 2001 ARM Limited
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef AMBA_CLCD_REGS_H
+#define AMBA_CLCD_REGS_H
+
+/*
+ * CLCD Controller Internal Register addresses
+ */
+#define CLCD_TIM0		0x00000000
+#define CLCD_TIM1 		0x00000004
+#define CLCD_TIM2 		0x00000008
+#define CLCD_TIM3 		0x0000000c
+#define CLCD_UBAS 		0x00000010
+#define CLCD_LBAS 		0x00000014
+
+#define CLCD_PL110_IENB		0x00000018
+#define CLCD_PL110_CNTL		0x0000001c
+#define CLCD_PL110_STAT		0x00000020
+#define CLCD_PL110_INTR 	0x00000024
+#define CLCD_PL110_UCUR		0x00000028
+#define CLCD_PL110_LCUR		0x0000002C
+
+#define CLCD_PL111_CNTL		0x00000018
+#define CLCD_PL111_IENB		0x0000001c
+#define CLCD_PL111_RIS		0x00000020
+#define CLCD_PL111_MIS		0x00000024
+#define CLCD_PL111_ICR		0x00000028
+#define CLCD_PL111_UCUR		0x0000002c
+#define CLCD_PL111_LCUR		0x00000030
+
+#define CLCD_PALL 		0x00000200
+#define CLCD_PALETTE		0x00000200
+
+#define TIM2_PCD_LO_MASK	GENMASK(4, 0)
+#define TIM2_PCD_LO_BITS	5
+#define TIM2_CLKSEL		(1 << 5)
+#define TIM2_ACB_MASK		GENMASK(10, 6)
+#define TIM2_IVS		(1 << 11)
+#define TIM2_IHS		(1 << 12)
+#define TIM2_IPC		(1 << 13)
+#define TIM2_IOE		(1 << 14)
+#define TIM2_BCD		(1 << 26)
+#define TIM2_PCD_HI_MASK	GENMASK(31, 27)
+#define TIM2_PCD_HI_BITS	5
+#define TIM2_PCD_HI_SHIFT	27
+
+#define CNTL_LCDEN		(1 << 0)
+#define CNTL_LCDBPP1		(0 << 1)
+#define CNTL_LCDBPP2		(1 << 1)
+#define CNTL_LCDBPP4		(2 << 1)
+#define CNTL_LCDBPP8		(3 << 1)
+#define CNTL_LCDBPP16		(4 << 1)
+#define CNTL_LCDBPP16_565	(6 << 1)
+#define CNTL_LCDBPP16_444	(7 << 1)
+#define CNTL_LCDBPP24		(5 << 1)
+#define CNTL_LCDBW		(1 << 4)
+#define CNTL_LCDTFT		(1 << 5)
+#define CNTL_LCDMONO8		(1 << 6)
+#define CNTL_LCDDUAL		(1 << 7)
+#define CNTL_BGR		(1 << 8)
+#define CNTL_BEBO		(1 << 9)
+#define CNTL_BEPO		(1 << 10)
+#define CNTL_LCDPWR		(1 << 11)
+#define CNTL_LCDVCOMP(x)	((x) << 12)
+#define CNTL_LDMAFIFOTIME	(1 << 15)
+#define CNTL_WATERMARK		(1 << 16)
+
+/* ST Microelectronics variant bits */
+#define CNTL_ST_1XBPP_444	0x0
+#define CNTL_ST_1XBPP_5551	(1 << 17)
+#define CNTL_ST_1XBPP_565	(1 << 18)
+#define CNTL_ST_CDWID_12	0x0
+#define CNTL_ST_CDWID_16	(1 << 19)
+#define CNTL_ST_CDWID_18	(1 << 20)
+#define CNTL_ST_CDWID_24	((1 << 19)|(1 << 20))
+#define CNTL_ST_CEAEN		(1 << 21)
+#define CNTL_ST_LCDBPP24_PACKED	(6 << 1)
+
+#endif /* AMBA_CLCD_REGS_H */

include/linux/amba/clcd.h

···
+/*
+ * linux/include/asm-arm/hardware/amba_clcd.h -- Integrator LCD panel.
+ *
+ * David A Rusling
+ *
+ * Copyright (C) 2001 ARM Limited
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+#include <linux/fb.h>
+#include <linux/amba/clcd-regs.h>
+
+enum {
+	/* individual formats */
+	CLCD_CAP_RGB444		= (1 << 0),
+	CLCD_CAP_RGB5551	= (1 << 1),
+	CLCD_CAP_RGB565		= (1 << 2),
+	CLCD_CAP_RGB888		= (1 << 3),
+	CLCD_CAP_BGR444		= (1 << 4),
+	CLCD_CAP_BGR5551	= (1 << 5),
+	CLCD_CAP_BGR565		= (1 << 6),
+	CLCD_CAP_BGR888		= (1 << 7),
+
+	/* connection layouts */
+	CLCD_CAP_444		= CLCD_CAP_RGB444 | CLCD_CAP_BGR444,
+	CLCD_CAP_5551		= CLCD_CAP_RGB5551 | CLCD_CAP_BGR5551,
+	CLCD_CAP_565		= CLCD_CAP_RGB565 | CLCD_CAP_BGR565,
+	CLCD_CAP_888		= CLCD_CAP_RGB888 | CLCD_CAP_BGR888,
+
+	/* red/blue ordering */
+	CLCD_CAP_RGB		= CLCD_CAP_RGB444 | CLCD_CAP_RGB5551 |
+				  CLCD_CAP_RGB565 | CLCD_CAP_RGB888,
+	CLCD_CAP_BGR		= CLCD_CAP_BGR444 | CLCD_CAP_BGR5551 |
+				  CLCD_CAP_BGR565 | CLCD_CAP_BGR888,
+
+	CLCD_CAP_ALL		= CLCD_CAP_BGR | CLCD_CAP_RGB,
+};
+
+struct backlight_device;
+
+struct clcd_panel {
+	struct fb_videomode	mode;
+	signed short		width;	/* width in mm */
+	signed short		height;	/* height in mm */
+	u32			tim2;
+	u32			tim3;
+	u32			cntl;
+	u32			caps;
+	unsigned int		bpp:8,
+				fixedtimings:1,
+				grayscale:1;
+	unsigned int		connector;
+	struct backlight_device	*backlight;
+	/*
+	 * If the B/R lines are switched between the CLCD
+	 * and the panel we need to know this and not try to
+	 * compensate with the BGR bit in the control register.
+	 */
+	bool			bgr_connection;
+};
+
+struct clcd_regs {
+	u32			tim0;
+	u32			tim1;
+	u32			tim2;
+	u32			tim3;
+	u32			cntl;
+	unsigned long		pixclock;
+};
+
+struct clcd_fb;
+
+/*
+ * the board-type specific routines
+ */
+struct clcd_board {
+	const char *name;
+
+	/*
+	 * Optional.  Hardware capability flags.
+	 */
+	u32	caps;
+
+	/*
+	 * Optional.  Check whether the var structure is acceptable
+	 * for this display.
+	 */
+	int	(*check)(struct clcd_fb *fb, struct fb_var_screeninfo *var);
+
+	/*
+	 * Compulsory.  Decode fb->fb.var into regs->*.  In the case of
+	 * fixed timing, set regs->* to the register values required.
+	 */
+	void	(*decode)(struct clcd_fb *fb, struct clcd_regs *regs);
+
+	/*
+	 * Optional.  Disable any extra display hardware.
+	 */
+	void	(*disable)(struct clcd_fb *);
+
+	/*
+	 * Optional.  Enable any extra display hardware.
+	 */
+	void	(*enable)(struct clcd_fb *);
+
+	/*
+	 * Setup platform specific parts of CLCD driver
+	 */
+	int	(*setup)(struct clcd_fb *);
+
+	/*
+	 * mmap the framebuffer memory
+	 */
+	int	(*mmap)(struct clcd_fb *, struct vm_area_struct *);
+
+	/*
+	 * Remove platform specific parts of CLCD driver
+	 */
+	void	(*remove)(struct clcd_fb *);
+};
+
+struct amba_device;
+struct clk;
+
+/* this data structure describes each frame buffer device we find */
+struct clcd_fb {
+	struct fb_info		fb;
+	struct amba_device	*dev;
+	struct clk		*clk;
+	struct clcd_panel	*panel;
+	struct clcd_board	*board;
+	void			*board_data;
+	void __iomem		*regs;
+	u16			off_ienb;
+	u16			off_cntl;
+	u32			clcd_cntl;
+	u32			cmap[16];
+	bool			clk_enabled;
+};
+
+static inline void clcdfb_decode(struct clcd_fb *fb, struct clcd_regs *regs)
+{
+	struct fb_var_screeninfo *var = &fb->fb.var;
+	u32 val, cpl;
+
+	/*
+	 * Program the CLCD controller registers and start the CLCD
+	 */
+	val = ((var->xres / 16) - 1) << 2;
+	val |= (var->hsync_len - 1) << 8;
+	val |= (var->right_margin - 1) << 16;
+	val |= (var->left_margin - 1) << 24;
+	regs->tim0 = val;
+
+	val = var->yres;
+	if (fb->panel->cntl & CNTL_LCDDUAL)
+		val /= 2;
+	val -= 1;
+	val |= (var->vsync_len - 1) << 10;
+	val |= var->lower_margin << 16;
+	val |= var->upper_margin << 24;
+	regs->tim1 = val;
+
+	val = fb->panel->tim2;
+	val |= var->sync & FB_SYNC_HOR_HIGH_ACT  ? 0 : TIM2_IHS;
+	val |= var->sync & FB_SYNC_VERT_HIGH_ACT ? 0 : TIM2_IVS;
+
+	cpl = var->xres_virtual;
+	if (fb->panel->cntl & CNTL_LCDTFT)	  /* TFT */
+		/* / 1 */;
+	else if (!var->grayscale)		  /* STN color */
+		cpl = cpl * 8 / 3;
+	else if (fb->panel->cntl & CNTL_LCDMONO8) /* STN monochrome, 8bit */
+		cpl /= 8;
+	else					  /* STN monochrome, 4bit */
+		cpl /= 4;
+
+	regs->tim2 = val | ((cpl - 1) << 16);
+
+	regs->tim3 = fb->panel->tim3;
+
+	val = fb->panel->cntl;
+	if (var->grayscale)
+		val |= CNTL_LCDBW;
+
+	if (fb->panel->caps && fb->board->caps && var->bits_per_pixel >= 16) {
+		/*
+		 * if board and panel supply capabilities, we can support
+		 * changing BGR/RGB depending on supplied parameters. Here
+		 * we switch to what the framebuffer is providing if need
+		 * be, so if the framebuffer is BGR but the display connection
+		 * is RGB (first case) we switch it around. Vice versa mutatis
+		 * mutandis if the framebuffer is RGB but the display connection
+		 * is BGR, we flip it around.
+		 */
+		if (var->red.offset == 0)
+			val &= ~CNTL_BGR;
+		else
+			val |= CNTL_BGR;
+		if (fb->panel->bgr_connection)
+			val ^= CNTL_BGR;
+	}
+
+	switch (var->bits_per_pixel) {
+	case 1:
+		val |= CNTL_LCDBPP1;
+		break;
+	case 2:
+		val |= CNTL_LCDBPP2;
+		break;
+	case 4:
+		val |= CNTL_LCDBPP4;
+		break;
+	case 8:
+		val |= CNTL_LCDBPP8;
+		break;
+	case 16:
+		/*
+		 * PL110 cannot choose between 5551 and 565 modes in its
+		 * control register.  It is possible to use 565 with
+		 * custom external wiring.
+		 */
+		if (amba_part(fb->dev) == 0x110 ||
+		    var->green.length == 5)
+			val |= CNTL_LCDBPP16;
+		else if (var->green.length == 6)
+			val |= CNTL_LCDBPP16_565;
+		else
+			val |= CNTL_LCDBPP16_444;
+		break;
+	case 32:
+		val |= CNTL_LCDBPP24;
+		break;
+	}
+
+	regs->cntl = val;
+	regs->pixclock = var->pixclock;
+}
+
+static inline int clcdfb_check(struct clcd_fb *fb, struct fb_var_screeninfo *var)
+{
+	var->xres_virtual = var->xres = (var->xres + 15) & ~15;
+	var->yres_virtual = var->yres = (var->yres + 1) & ~1;
+
+#define CHECK(e,l,h) (var->e < l || var->e > h)
+	if (CHECK(right_margin, (5+1), 256) ||	/* back porch */
+	    CHECK(left_margin, (5+1), 256) ||	/* front porch */
+	    CHECK(hsync_len, (5+1), 256) ||
+	    var->xres > 4096 ||
+	    var->lower_margin > 255 ||		/* back porch */
+	    var->upper_margin > 255 ||		/* front porch */
+	    var->vsync_len > 32 ||
+	    var->yres > 1024)
+		return -EINVAL;
+#undef CHECK
+
+	/* single panel mode: PCD = max(PCD, 1) */
+	/* dual panel mode: PCD = max(PCD, 5) */
+
+	/*
+	 * You can't change the grayscale setting, and
+	 * we can only do non-interlaced video.
+	 */
+	if (var->grayscale != fb->fb.var.grayscale ||
+	    (var->vmode & FB_VMODE_MASK) != FB_VMODE_NONINTERLACED)
+		return -EINVAL;
+
+#define CHECK(e) (var->e != fb->fb.var.e)
+	if (fb->panel->fixedtimings &&
+	    (CHECK(xres)		||
+	     CHECK(yres)		||
+	     CHECK(bits_per_pixel)	||
+	     CHECK(pixclock)		||
+	     CHECK(left_margin)		||
+	     CHECK(right_margin)	||
+	     CHECK(upper_margin)	||
+	     CHECK(lower_margin)	||
+	     CHECK(hsync_len)		||
+	     CHECK(vsync_len)		||
+	     CHECK(sync)))
+		return -EINVAL;
+#undef CHECK
+
+	var->nonstd = 0;
+	var->accel_flags = 0;
+
+	return 0;
+}