[Intel-gfx] [PATCH - v3] drm/i915: Discard large BIOS framebuffers causing display corruption.

[Ashish Arora]

> On 12-Jan-2022, at 7:07 PM, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> 
> On Tue, Jan 11, 2022 at 07:55:22AM +0000, Ashish Arora wrote:
>> From: Ashish Arora <ashisharora.linux at outlook.com>
>> 
>> On certain 4k panels and Macs, the BIOS framebuffer is larger than what
>> panel requires causing display corruption. Introduce a check for the same.
> 
> If a larger fb causes corruption then there is a real bug somewhere.
I would like to clarify that what I meant by display corruption that some edges of screen are not seen.

Orlando described better in a mail as follows :- 

"I haven't observed "display corruption", but on my MacBookPro16,1 the bottom
and right edges of the TTY are not on the screen, so a few lines of text
cannot be seen.

This also occurs on the internal displays of all (as far as I know) other
2018-2020 Intel Macbooks when using the Intel GPU (The 15" and 16" ones
also have an AMDGPU, but this issue occurs when they have the Intel GPU
set as the boot gpu).”
> 
>> 
>> 
>> Signed-off-by: Ashish Arora <ashisharora.linux at outlook.com>
>> Reviewed-by: Aun-Ali Zaidi <admin at kodeit.net>
>> ---
>> V2 :- Use != instead of < and >
>> V3 :- Mention Macs (Thanks to Orlando)
>> drivers/gpu/drm/i915/display/intel_fbdev.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
>> index 842c04e63..16b1c82b2 100644
>> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
>> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
>> @@ -181,10 +181,10 @@ static int intelfb_create(struct drm_fb_helper *helper,
>> 	int ret;
>> 
>> 	if (intel_fb &&
>> -	    (sizes->fb_width > intel_fb->base.width ||
>> -	     sizes->fb_height > intel_fb->base.height)) {
>> +	    (sizes->fb_width != intel_fb->base.width ||
>> +	     sizes->fb_height != intel_fb->base.height)) {
>> 		drm_dbg_kms(&dev_priv->drm,
>> -			    "BIOS fb too small (%dx%d), we require (%dx%d),"
>> +			    "BIOS fb not valid (%dx%d), we require (%dx%d),"
>> 			    " releasing it\n",
>> 			    intel_fb->base.width, intel_fb->base.height,
>> 			    sizes->fb_width, sizes->fb_height);
>> -- 
>> 2.25.1
>> 
> 
> -- 
> Ville Syrjälä
> Intel