drm/mgag200: Replace VRAM helpers with SHMEM helpers

The VRAM helpers managed the framebuffer memory for mgag200. This came
with several problems, as some MGA device require the scanout address
to be located at VRAM offset 0. It's incompatible with the page-flip
semantics of DRM's atomic modesettting. With atomic modesetting, old and
new framebuffers have to be located in VRAM at the same time. So at least
one of them has to reside at a non-0 offset.

This patch replaces VRAM helpers with SHMEM helpers. GEM SHMEM buffers
reside in system memory, and are shadow-copied into VRAM during page
flips. The shadow copy always starts at VRAM offset 0.

v2:
* revert dev->pdev changes

Signed-off-by: Thomas Zimmermann <[e-mail]>
Tested-by: John Donnelly <[e-mail]>
Acked-by: Emil Velikov <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/mgag200/Kconfig

···
 config DRM_MGAG200
 	tristate "Kernel modesetting driver for MGA G200 server engines"
 	depends on DRM && PCI && MMU
+	select DRM_GEM_SHMEM_HELPER
 	select DRM_KMS_HELPER
-	select DRM_VRAM_HELPER
-	select DRM_TTM
-	select DRM_TTM_HELPER
 	help
 	 This is a KMS driver for the MGA G200 server chips, it
 	 does not support the original MGA G200 or any of the desktop

drivers/gpu/drm/mgag200/mgag200_drv.c

···
  * which then performs further device association and calls our graphics init
  * functions
  */
-int mgag200_modeset = -1;
 
+int mgag200_modeset = -1;
 MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
 module_param_named(modeset, mgag200_modeset, int, 0400);
-
-int mgag200_hw_bug_no_startadd = -1;
-MODULE_PARM_DESC(modeset, "HW does not interpret scanout-buffer start address correctly");
-module_param_named(hw_bug_no_startadd, mgag200_hw_bug_no_startadd, int, 0400);
 
 static struct drm_driver driver;
 
···
 
 DEFINE_DRM_GEM_FOPS(mgag200_driver_fops);
 
-static bool mgag200_pin_bo_at_0(const struct mga_device *mdev)
-{
-	if (mgag200_hw_bug_no_startadd > 0) {
-		DRM_WARN_ONCE("Option hw_bug_no_startradd is enabled. Please "
-			      "report the output of 'lspci -vvnn' to "
-			      "<[e-mail]> if this "
-			      "option is required to make mgag200 work "
-			      "correctly on your system.\n");
-		return true;
-	} else if (!mgag200_hw_bug_no_startadd) {
-		return false;
-	}
-	return mdev->flags & MGAG200_FLAG_HW_BUG_NO_STARTADD;
-}
-
-int mgag200_driver_dumb_create(struct drm_file *file,
-			       struct drm_device *dev,
-			       struct drm_mode_create_dumb *args)
-{
-	struct mga_device *mdev = to_mga_device(dev);
-	unsigned long pg_align;
-
-	if (WARN_ONCE(!dev->vram_mm, "VRAM MM not initialized"))
-		return -EINVAL;
-
-	pg_align = 0ul;
-
-	/*
-	 * Aligning scanout buffers to the size of the video ram forces
-	 * placement at offset 0. Works around a bug where HW does not
-	 * respect 'startadd' field.
-	 */
-	if (mgag200_pin_bo_at_0(mdev))
-		pg_align = PFN_UP(mdev->mc.vram_size);
-
-	return drm_gem_vram_fill_create_dumb(file, dev, pg_align, 0, args);
-}
-
 static struct drm_driver driver = {
 	.driver_features = DRIVER_ATOMIC | DRIVER_GEM | DRIVER_MODESET,
 	.fops = &mgag200_driver_fops,
···
 	.major = DRIVER_MAJOR,
 	.minor = DRIVER_MINOR,
 	.patchlevel = DRIVER_PATCHLEVEL,
-	.debugfs_init = drm_vram_mm_debugfs_init,
-	.dumb_create = mgag200_driver_dumb_create,
-	.dumb_map_offset = drm_gem_vram_driver_dumb_mmap_offset,
-	.gem_prime_mmap = drm_gem_prime_mmap,
+	DRM_GEM_SHMEM_DRIVER_OPS,
 };
 
 static struct pci_driver mgag200_pci_driver = {

drivers/gpu/drm/mgag200/mgag200_drv.h

···
 #include <drm/drm_encoder.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_gem.h>
-#include <drm/drm_gem_vram_helper.h>
+#include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_simple_kms_helper.h>
 
 #include "mgag200_reg.h"
···
 
 	struct mga_mc			mc;
 
-	size_t vram_fb_available;
+	void __iomem			*vram;
+	size_t				vram_fb_available;
 
 	enum mga_type			type;
 	int				has_sdram;

drivers/gpu/drm/mgag200/mgag200_mode.c

···
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_crtc_helper.h>
+#include <drm/drm_damage_helper.h>
+#include <drm/drm_format_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_plane_helper.h>
···
 }
 
 static void
+mgag200_handle_damage(struct mga_device *mdev, struct drm_framebuffer *fb,
+		      struct drm_rect *clip)
+{
+	struct drm_device *dev = mdev->dev;
+	void *vmap;
+
+	vmap = drm_gem_shmem_vmap(fb->obj[0]);
+	if (drm_WARN_ON(dev, !vmap))
+		return; /* BUG: SHMEM BO should always be vmapped */
+
+	drm_fb_memcpy_dstclip(mdev->vram, vmap, fb, clip);
+
+	drm_gem_shmem_vunmap(fb->obj[0], vmap);
+
+	/* Always scanout image at VRAM offset 0 */
+	mgag200_set_startadd(mdev, (u32)0);
+	mgag200_set_offset(mdev, fb);
+}
+
+static void
 mgag200_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 				   struct drm_crtc_state *crtc_state,
 				   struct drm_plane_state *plane_state)
···
 	struct mga_device *mdev = to_mga_device(dev);
 	struct drm_display_mode *adjusted_mode = &crtc_state->adjusted_mode;
 	struct drm_framebuffer *fb = plane_state->fb;
-	struct drm_gem_vram_object *gbo;
-	s64 gpu_addr;
-
-	gbo = drm_gem_vram_of_gem(fb->obj[0]);
-
-	gpu_addr = drm_gem_vram_offset(gbo);
-	if (drm_WARN_ON_ONCE(dev, gpu_addr < 0))
-		return; /* BUG: BO should have been pinned to VRAM. */
+	struct drm_rect fullscreen = {
+		.x1 = 0,
+		.x2 = fb->width,
+		.y1 = 0,
+		.y2 = fb->height,
+	};
 
 	mga_crtc_prepare(crtc);
 
···
 		mgag200_g200ev_set_hiprilvl(mdev);
 
 	mga_crtc_commit(crtc);
+
+	mgag200_handle_damage(mdev, fb, &fullscreen);
 }
 
 static void
···
 	struct mga_device *mdev = to_mga_device(dev);
 	struct drm_plane_state *state = plane->state;
 	struct drm_framebuffer *fb = state->fb;
-	struct drm_gem_vram_object *gbo;
-	s64 gpu_addr;
+	struct drm_rect damage;
 
 	if (!fb)
 		return;
 
-	gbo = drm_gem_vram_of_gem(fb->obj[0]);
-
-	gpu_addr = drm_gem_vram_offset(gbo);
-	if (drm_WARN_ON_ONCE(dev, gpu_addr < 0))
-		return; /* BUG: BO should have been pinned to VRAM. */
-
-	mgag200_set_startadd(mdev, (unsigned long)gpu_addr);
-	mgag200_set_offset(mdev, fb);
+	if (drm_atomic_helper_damage_merged(old_state, state, &damage))
+		mgag200_handle_damage(mdev, fb, &damage);
 }
 
 static const struct drm_simple_display_pipe_funcs
···
 	.disable    = mgag200_simple_display_pipe_disable,
 	.check	    = mgag200_simple_display_pipe_check,
 	.update	    = mgag200_simple_display_pipe_update,
-	.prepare_fb = drm_gem_vram_simple_display_pipe_prepare_fb,
-	.cleanup_fb = drm_gem_vram_simple_display_pipe_cleanup_fb,
+	.prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
 };
 
 static const uint32_t mgag200_simple_display_pipe_formats[] = {
···
  */
 
 static const struct drm_mode_config_funcs mgag200_mode_config_funcs = {
-	.fb_create     = drm_gem_fb_create,
-	.mode_valid    = drm_vram_helper_mode_valid,
+	.fb_create     = drm_gem_fb_create_with_dirty,
 	.atomic_check  = drm_atomic_helper_check,
 	.atomic_commit = drm_atomic_helper_commit,
 };
···
 	dev->mode_config.max_height = MGAG200_MAX_FB_HEIGHT;
 
 	dev->mode_config.preferred_depth = mgag200_preferred_depth(mdev);
-	dev->mode_config.prefer_shadow = 1;
 
 	dev->mode_config.fb_base = mdev->mc.vram_base;
 

drivers/gpu/drm/mgag200/mgag200_ttm.c

···
 
 int mgag200_mm_init(struct mga_device *mdev)
 {
-	struct drm_vram_mm *vmm;
-	int ret;
 	struct drm_device *dev = mdev->dev;
-
-	vmm = drm_vram_helper_alloc_mm(dev, pci_resource_start(dev->pdev, 0),
-				       mdev->mc.vram_size);
-	if (IS_ERR(vmm)) {
-		ret = PTR_ERR(vmm);
-		DRM_ERROR("Error initializing VRAM MM; %d\n", ret);
-		return ret;
-	}
+	int ret;
 
 	arch_io_reserve_memtype_wc(pci_resource_start(dev->pdev, 0),
 				   pci_resource_len(dev->pdev, 0));
···
 	mdev->fb_mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 0),
 					 pci_resource_len(dev->pdev, 0));
 
+	mdev->vram = ioremap(pci_resource_start(dev->pdev, 0),
+			     pci_resource_len(dev->pdev, 0));
+	if (!mdev->vram) {
+		ret = -ENOMEM;
+		goto err_arch_phys_wc_del;
+	}
+
 	mdev->vram_fb_available = mdev->mc.vram_size;
 
 	return 0;
+
+err_arch_phys_wc_del:
+	arch_phys_wc_del(mdev->fb_mtrr);
+	arch_io_free_memtype_wc(pci_resource_start(dev->pdev, 0),
+				pci_resource_len(dev->pdev, 0));
+	return ret;
 }
 
 void mgag200_mm_fini(struct mga_device *mdev)
···
 	struct drm_device *dev = mdev->dev;
 
 	mdev->vram_fb_available = 0;
-
-	drm_vram_helper_release_mm(dev);
-
+	iounmap(mdev->vram);
 	arch_io_free_memtype_wc(pci_resource_start(dev->pdev, 0),
 				pci_resource_len(dev->pdev, 0));
 	arch_phys_wc_del(mdev->fb_mtrr);