From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Tue, 21 Apr 2026 07:29:07 +0000 (+0200)
Subject: drm/tegra: fbdev: Calculate buffer geometry with format helpers
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8e94aa3637a25e5b9eff09161d3cc28c1759f850;p=thirdparty%2Fkernel%2Flinux.git

drm/tegra: fbdev: Calculate buffer geometry with format helpers

Replace the geometry and size calculation in tegra's fbdev emulation
with DRM format helpers. This consists of a 4CC lookup from the fbdev
parameters, format lookup, pitch calculation and size calculation.
Then allocate the GEM buffer object for the framebuffer memory from
the calculated size.

Set up mode_cmd with the calculated values just before allocating the
framebuffer. This code will later be replaced with a DRM client buffer.

Set framebuffer size fields in struct fb_info from the size stored in
the GEM buffer object instead of what has been requested. The requested
size is an estimate, while the buffer size is the exact value rounded
to the correct alignment.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patch.msgid.link/20260421073646.144712-4-tzimmermann@suse.de
---

diff --git a/drivers/gpu/drm/tegra/fbdev.c b/drivers/gpu/drm/tegra/fbdev.c
index 793849199783a..bcf32cfcf8180 100644
--- a/drivers/gpu/drm/tegra/fbdev.c
+++ b/drivers/gpu/drm/tegra/fbdev.c
@@ -74,31 +74,29 @@ int tegra_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
 	struct drm_device *drm = helper->dev;
 	struct drm_mode_fb_cmd2 cmd = { 0 };
 	struct fb_info *info = helper->info;
-	unsigned int bytes_per_pixel;
+	u32 fourcc, pitch;
+	u64 size;
+	const struct drm_format_info *format;
 	struct drm_framebuffer *fb;
 	struct tegra_bo *bo;
-	size_t size;
 	int err;
 
-	bytes_per_pixel = DIV_ROUND_UP(sizes->surface_bpp, 8);
-
-	cmd.width = sizes->surface_width;
-	cmd.height = sizes->surface_height;
-	cmd.pitches[0] = round_up(sizes->surface_width * bytes_per_pixel,
-				  tegra->pitch_align);
-
-	cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
-						     sizes->surface_depth);
-
-	size = cmd.pitches[0] * cmd.height;
+	fourcc = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
+	format = drm_get_format_info(drm, fourcc, DRM_FORMAT_MOD_LINEAR);
+	pitch = round_up(drm_format_info_min_pitch(format, 0, sizes->surface_width),
+			 tegra->pitch_align);
+	size = ALIGN(pitch * sizes->surface_height, PAGE_SIZE);
 
 	bo = tegra_bo_create(drm, size, 0);
 	if (IS_ERR(bo))
 		return PTR_ERR(bo);
 
-	fb = tegra_fb_alloc(drm,
-			    drm_get_format_info(drm, cmd.pixel_format, cmd.modifier[0]),
-			    &cmd, &bo, 1);
+	cmd.pixel_format = fourcc;
+	cmd.width = sizes->surface_width;
+	cmd.height = sizes->surface_height;
+	cmd.pitches[0] = pitch;
+
+	fb = tegra_fb_alloc(drm, format, &cmd, &bo, 1);
 	if (IS_ERR(fb)) {
 		err = PTR_ERR(fb);
 		dev_err(drm->dev, "failed to allocate DRM framebuffer: %d\n",
@@ -126,9 +124,9 @@ int tegra_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
 
 	info->flags |= FBINFO_VIRTFB;
 	info->screen_buffer = bo->vaddr;
-	info->screen_size = size;
+	info->screen_size = bo->gem.size;
 	info->fix.smem_start = (unsigned long)(bo->iova);
-	info->fix.smem_len = size;
+	info->fix.smem_len = bo->gem.size;
 
 	return 0;