From 3062b65df88af69e9a302d0a8a34adc906b62787 Mon Sep 17 00:00:00 2001
From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Wed, 9 Feb 2022 17:16:14 +0100
Subject: drm/fb-helper: Fix vertical damage clipping
Git-commit: aa15c677cc34e626789cb65b8e7375180851c03b
Patch-mainline: v5.18-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
Don't clip the damage rectangle against the viewport. This only
works if the viewport is located at the beginning of the video
memory and the video memory doesn't extend the screen (i.e., if
there's no overallocation).
Fbdev emulation transfers data from write operations into a
possible shadow buffer, then into a GEM buffer object, and finally
via graphics driver onto the screen.
If callers write outside the currently visible area, clipping the
damage rectangle against the viewport will loose these updates in
the shadow buffer and the fbdev's buffer object will contain stale
data. Panning the viewport to the stale area of the buffer will
display obsolete data.
Instead, mark all written areas as damaged, so that the damage
handler updates the buffer object from the shadow buffer for all
such areas. The graphics driver's later has the option of clipping
the damaged area against the viewport when updating the screen
from the buffer object.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209161617.3553-3-tzimmermann@suse.de
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/drm_fb_helper.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 3433e0aa7d3f..8e5ab497d30b 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -706,8 +706,7 @@ void drm_fb_helper_deferred_io(struct fb_info *info,
if (min < max) {
y1 = min / info->fix.line_length;
- y2 = min_t(u32, DIV_ROUND_UP(max, info->fix.line_length),
- info->var.yres);
+ y2 = DIV_ROUND_UP(max, info->fix.line_length);
drm_fb_helper_damage(info, 0, y1, info->var.xres, y2 - y1);
}
}
--
2.38.1