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| author | Thomas Zimmermann <tzimmermann@suse.de> | 2019-01-16 09:32:37 +0100 |
|---|---|---|
| committer | Thomas Zimmermann <tzimmermann@suse.de> | 2019-01-16 09:59:21 +0100 |
| commit | 89af5e6a2420df6db72292717a9d44a667a1ab2c (patch) | |
| tree | efc64719a5cb1ccc84d39a7e6430b7796a3c4744 | |
| parent | c5890e62790abce676538a0759234cc0382e8c84 (diff) | |
drm/fb-helper: Ignore the value of fb_var_screeninfo.pixclock (bsc#1106929)
| -rw-r--r-- | patches.fixes/0001-drm-fb-helper-Ignore-the-value-of-fb_var_screeninfo..patch | 78 | ||||
| -rw-r--r-- | series.conf | 1 |
2 files changed, 79 insertions, 0 deletions
diff --git a/patches.fixes/0001-drm-fb-helper-Ignore-the-value-of-fb_var_screeninfo..patch b/patches.fixes/0001-drm-fb-helper-Ignore-the-value-of-fb_var_screeninfo..patch new file mode 100644 index 0000000000..36af2ad489 --- /dev/null +++ b/patches.fixes/0001-drm-fb-helper-Ignore-the-value-of-fb_var_screeninfo..patch @@ -0,0 +1,78 @@ +From 66a8d5bfb518f9f12d47e1d2dce1732279f9451e Mon Sep 17 00:00:00 2001 +From: Ivan Mironov <mironov.ivan@gmail.com> +Date: Tue, 8 Jan 2019 12:23:53 +0500 +Subject: drm/fb-helper: Ignore the value of fb_var_screeninfo.pixclock +Git-commit: 66a8d5bfb518f9f12d47e1d2dce1732279f9451e +Patch-mainline: v5.0-rc2 +References: bsc#1106929 + +Strict requirement of pixclock to be zero breaks support of SDL 1.2 +which contains hardcoded table of supported video modes with non-zero +pixclock values[1]. + +To better understand which pixclock values are considered valid and how +driver should handle these values, I briefly examined few existing fbdev +drivers and documentation in Documentation/fb/. And it looks like there +are no strict rules on that and actual behaviour varies: + + * some drivers treat (pixclock == 0) as "use defaults" (uvesafb.c); + * some treat (pixclock == 0) as invalid value which leads to + -EINVAL (clps711x-fb.c); + * some pass converted pixclock value to hardware (uvesafb.c); + * some are trying to find nearest value from predefined table + (vga16fb.c, video_gx.c). + +Given this, I believe that it should be safe to just ignore this value if +changing is not supported. It seems that any portable fbdev application +which was not written only for one specific device working under one +specific kernel version should not rely on any particular behaviour of +pixclock anyway. + +However, while enabling SDL1 applications to work out of the box when +there is no /etc/fb.modes with valid settings, this change affects the +video mode choosing logic in SDL. Depending on current screen +resolution, contents of /etc/fb.modes and resolution requested by +application, this may lead to user-visible difference (not always): +image will be displayed in a right way, but it will be aligned to the +left instead of center. There is no "right behaviour" here as well, as +emulated fbdev, opposing to old fbdev drivers, simply ignores any +requsts of video mode changes with resolutions smaller than current. + +The easiest way to reproduce this problem is to install sdl-sopwith[2], +remove /etc/fb.modes file if it exists, and then try to run sopwith +from console without X. At least in Fedora 29, sopwith may be simply +installed from standard repositories. + +[1] SDL 1.2.15 source code, src/video/fbcon/SDL_fbvideo.c, vesa_timings +[2] http://sdl-sopwith.sourceforge.net/ + +Signed-off-by: Ivan Mironov <mironov.ivan@gmail.com> +Cc: stable@vger.kernel.org +Fixes: 79e539453b34e ("DRM: i915: add mode setting support") +Fixes: 771fe6b912fca ("drm/radeon: introduce kernel modesetting for radeon hardware") +Fixes: 785b93ef8c309 ("drm/kms: move driver specific fb common code to helper functions (v2)") +Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> +Link: https://patchwork.freedesktop.org/patch/msgid/20190108072353.28078-3-mironov.ivan@gmail.com +Acked-by: Thomas Zimmermann <tzimmermann@suse.de> +--- + drivers/gpu/drm/drm_fb_helper.c | 7 ++++++- + 1 file changed, 6 insertions(+), 1 deletion(-) + +--- a/drivers/gpu/drm/drm_fb_helper.c ++++ b/drivers/gpu/drm/drm_fb_helper.c +@@ -1109,9 +1109,14 @@ int drm_fb_helper_check_var(struct fb_va + struct drm_framebuffer *fb = fb_helper->fb; + int depth; + +- if (var->pixclock != 0 || in_dbg_master()) ++ if (in_dbg_master()) + return -EINVAL; + ++ if (var->pixclock != 0) { ++ DRM_DEBUG("fbdev emulation doesn't support changing the pixel clock, value of pixclock is ignored\n"); ++ var->pixclock = 0; ++ } ++ + /* Need to resize the fb object !!! */ + if (var->bits_per_pixel > fb->bits_per_pixel || + var->xres > fb->width || var->yres > fb->height || diff --git a/series.conf b/series.conf index cf47cbe638..a38982ed34 100644 --- a/series.conf +++ b/series.conf @@ -23856,6 +23856,7 @@ patches.drivers/iommu-amd-fix-amd_iommu-force_isolation patches.fixes/0001-fbdev-fbmem-behave-better-with-small-rotated-display.patch patches.fixes/0001-fbdev-fbcon-Fix-unregister-crash-when-more-than-one-.patch + patches.fixes/0001-drm-fb-helper-Ignore-the-value-of-fb_var_screeninfo..patch ######################################################## # end of sorted patches |