[Intel-gfx] [PATCH] drm/i915: Discard BIOS framebuffers too small to accommodate chosen mode

[Ville Syrjälä]

On Tue, Apr 22, 2014 at 10:05:58PM +0100, Chris Wilson wrote:
> If the inherited BIOS framebuffer is smaller than the mode selected for
> fbdev, then if we continue to use it then we cause display corruption as
> we do not setup the panel fitter to upscale.
> 
> Regression from commit d978ef14456a38034f6c0e94a794129501f89200
> Author: Jesse Barnes <jbarnes at virtuousgeek.org>
> Date:   Fri Mar 7 08:57:51 2014 -0800
> 
>     drm/i915: Wrap the preallocated BIOS framebuffer and preserve for KMS fbcon v12
> 
> Reported-by: Knut Petersen <Knut_Petersen at t-online.de>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77767
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/intel_fbdev.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index b16116db6c37..28220ca838df 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -133,6 +133,12 @@ static int intelfb_create(struct drm_fb_helper *helper,
>  
>  	mutex_lock(&dev->struct_mutex);
>  
> +	if (intel_fb &&
> +	    (sizes->fb_width > intel_fb->base.width ||
> +	     sizes->fb_height > intel_fb->base.height)) {
> +		drm_framebuffer_reference(&ifbdev->fb->base);

unreference

I know intel_fb == ifbdev->fb, but still I think it would look a bit
less confusing if you passed &intel_fb->base to
drm_framebuffer_unreference() instead of &ifbdev->fb->base. Simply
because you use intel_fb->base in the size checks just before.

> +		intel_fb = ifbdev->fb = NULL;
> +	}
>  	if (!intel_fb || WARN_ON(!intel_fb->obj)) {
>  		DRM_DEBUG_KMS("no BIOS fb, allocating a new one\n");
>  		ret = intelfb_alloc(helper, sizes);
> -- 
> 1.9.2
> 
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-- 
Ville Syrjälä
Intel OTC