Staging: fbtft: add ssd1325 controller support

That patch adds support for SSD1325 controller.
That is 4bpp grayscale OLED display controller present in several
displays eq: Winstar WEX012864

Signed-off-by: Alexey Mednyy <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/fbtft/Kconfig

···
 	help
 	  Framebuffer support for SSD1306
 
+config FB_TFT_SSD1325
+        tristate "FB driver for the SSD1325 OLED Controller"
+        depends on FB_TFT
+        help
+          Framebuffer support for SSD1305
+
 config FB_TFT_SSD1331
 	tristate "FB driver for the SSD1331 LCD Controller"
 	depends on FB_TFT

drivers/staging/fbtft/Makefile

···
 obj-$(CONFIG_FB_TFT_SSD1289)     += fb_ssd1289.o
 obj-$(CONFIG_FB_TFT_SSD1305)     += fb_ssd1305.o
 obj-$(CONFIG_FB_TFT_SSD1306)     += fb_ssd1306.o
+obj-$(CONFIG_FB_TFT_SSD1305)     += fb_ssd1325.o
 obj-$(CONFIG_FB_TFT_SSD1331)     += fb_ssd1331.o
 obj-$(CONFIG_FB_TFT_SSD1351)     += fb_ssd1351.o
 obj-$(CONFIG_FB_TFT_ST7735R)     += fb_st7735r.o

drivers/staging/fbtft/fb_ssd1325.c

···
+/*
+ * FB driver for the SSD1325 OLED Controller
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/gpio.h>
+#include <linux/delay.h>
+
+#include "fbtft.h"
+
+#define DRVNAME		"fb_ssd1325"
+
+#define WIDTH 128
+#define HEIGHT 64
+#define GAMMA_NUM   1
+#define GAMMA_LEN   15
+#define DEFAULT_GAMMA "7 1 1 1 1 2 2 3 3 4 4 5 5 6 6"
+
+/*
+ * write_reg() caveat:
+ *
+ *    This doesn't work because D/C has to be LOW for both values:
+ *      write_reg(par, val1, val2);
+ *
+ *    Do it like this:
+ *      write_reg(par, val1);
+ *      write_reg(par, val2);
+ */
+
+/* Init sequence taken from the Adafruit SSD1306 Arduino library */
+static int init_display(struct fbtft_par *par)
+{
+	par->fbtftops.reset(par);
+
+	gpio_set_value(par->gpio.cs, 0);
+
+	write_reg(par, 0xb3);
+	write_reg(par, 0xf0);
+	write_reg(par, 0xae);
+	write_reg(par, 0xa1);
+	write_reg(par, 0x00);
+	write_reg(par, 0xa8);
+	write_reg(par, 0x3f);
+	write_reg(par, 0xa0);
+	write_reg(par, 0x45);
+	write_reg(par, 0xa2);
+	write_reg(par, 0x40);
+	write_reg(par, 0x75);
+	write_reg(par, 0x00);
+	write_reg(par, 0x3f);
+	write_reg(par, 0x15);
+	write_reg(par, 0x00);
+	write_reg(par, 0x7f);
+	write_reg(par, 0xa4);
+	write_reg(par, 0xaf);
+
+	return 0;
+}
+
+static uint8_t rgb565_to_g16(u16 pixel)
+{
+	u16 b = pixel & 0x1f;
+	u16 g = (pixel & (0x3f << 5)) >> 5;
+	u16 r = (pixel & (0x1f << (5 + 6))) >> (5 + 6);
+
+	pixel = (299 * r + 587 * g + 114 * b) / 195;
+	if (pixel > 255)
+		pixel = 255;
+	return (uint8_t)pixel / 16;
+}
+
+static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
+{
+	fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par,
+		      "%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe,
+		      ye);
+
+	write_reg(par, 0x75);
+	write_reg(par, 0x00);
+	write_reg(par, 0x3f);
+	write_reg(par, 0x15);
+	write_reg(par, 0x00);
+	write_reg(par, 0x7f);
+}
+
+static int blank(struct fbtft_par *par, bool on)
+{
+	fbtft_par_dbg(DEBUG_BLANK, par, "%s(blank=%s)\n",
+		      __func__, on ? "true" : "false");
+
+	if (on)
+		write_reg(par, 0xAE);
+	else
+		write_reg(par, 0xAF);
+	return 0;
+}
+
+/*
+ * Grayscale Lookup Table
+ * GS1 - GS15
+ * The "Gamma curve" contains the relative values between the entries
+ * in the Lookup table.
+ *
+ * 0 = Setting of GS1 < Setting of GS2 < Setting of GS3.....<
+ * Setting of GS14 < Setting of GS15
+ */
+static int set_gamma(struct fbtft_par *par, unsigned long *curves)
+{
+	int i;
+
+	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
+
+	for (i = 0; i < GAMMA_LEN; i++) {
+		if (i > 0 && curves[i] < 1) {
+			dev_err(par->info->device,
+				"Illegal value in Grayscale Lookup Table at index %d.\n"
+				"Must be greater than 0\n", i);
+			return -EINVAL;
+		}
+		if (curves[i] > 7) {
+			dev_err(par->info->device,
+				"Illegal value(s) in Grayscale Lookup Table.\n"
+				"At index=%d, the accumulated value has exceeded 7\n",
+				i);
+			return -EINVAL;
+		}
+	}
+	write_reg(par, 0xB8);
+	for (i = 0; i < 8; i++)
+		write_reg(par, (curves[i] & 0xFF));
+	return 0;
+}
+
+static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
+{
+	u16 *vmem16 = (u16 *)par->info->screen_buffer;
+	u8 *buf = par->txbuf.buf;
+	u8 n1;
+	u8 n2;
+	int y, x;
+	int ret;
+
+	for (x = 0; x < par->info->var.xres; x++) {
+		if (x % 2)
+			continue;
+		for (y = 0; y < par->info->var.yres; y++) {
+			n1 = rgb565_to_g16(vmem16[y * par->info->var.xres + x]);
+			n2 = rgb565_to_g16(vmem16
+					   [y * par->info->var.xres + x + 1]);
+			*buf = (n1 << 4) | n2;
+			buf++;
+		}
+	}
+
+	gpio_set_value(par->gpio.dc, 1);
+
+	/* Write data */
+	ret = par->fbtftops.write(par, par->txbuf.buf,
+				par->info->var.xres * par->info->var.yres / 2);
+	if (ret < 0)
+		dev_err(par->info->device,
+			"%s: write failed and returned: %d\n", __func__, ret);
+
+	return ret;
+}
+
+static struct fbtft_display display = {
+	.regwidth = 8,
+	.width = WIDTH,
+	.height = HEIGHT,
+	.txbuflen = WIDTH * HEIGHT / 2,
+	.gamma_num = GAMMA_NUM,
+	.gamma_len = GAMMA_LEN,
+	.gamma = DEFAULT_GAMMA,
+	.fbtftops = {
+		.write_vmem = write_vmem,
+		.init_display = init_display,
+		.set_addr_win = set_addr_win,
+		.blank = blank,
+		.set_gamma = set_gamma,
+	},
+};
+
+FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
+
+MODULE_ALIAS("spi:" DRVNAME);
+MODULE_ALIAS("platform:" DRVNAME);
+MODULE_ALIAS("spi:ssd1325");
+MODULE_ALIAS("platform:ssd1325");
+
+MODULE_DESCRIPTION("SSD1325 OLED Driver");
+MODULE_AUTHOR("Alexey Mednyy");
+MODULE_LICENSE("GPL");