linux-kernel - Re: [PATCH] drm/i915: Discard large BIOS framebuffers causing display corruption.

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Message-ID: <87sftzlnkp.fsf@intel.com>
Date:   Fri, 07 Jan 2022 14:47:34 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Ashish Arora <ashisharora.linux@...look.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>
Cc:     "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/i915: Discard large BIOS framebuffers causing
 display corruption.

On Fri, 07 Jan 2022, Ashish Arora <ashisharora.linux@...look.com> wrote:
> From: Ashish Arora <ashisharora.linux@...look.com>
>
> On certain 4k panels, the BIOS framebuffer is larger than what panel
> requires causing display corruption. Introduce a check for the same.

This is quite thin on details. Is there a bug report?

Moreover, if this is what we want, this should be combined with the
conditions that follow resulting in a "!=" check instead of separate "<"
and ">".

BR,
Jani.



>
> Signed-off-by: Ashish Arora <ashisharora.linux@...look.com>
> ---
>  drivers/gpu/drm/i915/display/intel_fbdev.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index adc3a81be..f9952e1f8 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -193,6 +193,17 @@ static int intelfb_create(struct drm_fb_helper *helper,
>  	struct drm_i915_gem_object *obj;
>  	int ret;
>  
> +	if (intel_fb &&
> +	    (sizes->fb_width < intel_fb->base.width ||
> +	     sizes->fb_height < intel_fb->base.height)) {
> +		drm_dbg_kms(&dev_priv->drm,
> +			    "BIOS fb too large (%dx%d), we require (%dx%d),"
> +			    " releasing it\n",
> +			    intel_fb->base.width, intel_fb->base.height,
> +			    sizes->fb_width, sizes->fb_height);
> +		drm_framebuffer_put(&intel_fb->base);
> +		intel_fb = ifbdev->fb = NULL;
> +	}
>  	if (intel_fb &&
>  	    (sizes->fb_width > intel_fb->base.width ||
>  	     sizes->fb_height > intel_fb->base.height)) {

-- 
Jani Nikula, Intel Open Source Graphics Center