Re: [PATCH 2/2] drm/mgag200: Use 24bit format in VRAM

[Jocelyn Falempe <jfalempe@redhat.com>]

On 12/04/2023 17:13, Javier Martinez Canillas wrote:
> Jocelyn Falempe <jfalempe@redhat.com> writes:
> 
>> The bandwidth between system memory and VRAM is very limited
>> on G200.
>> So when using a 32bit framebuffer on system memory, convert it to 24bit
>> when copying the frame to the VRAM, this allows to go 33% faster.
>> Converting the format on the fly is negligible, even on low end CPU.
>>
>> small benchmark on my Dell T310:
>> 1280x1024 32bits: ~125ms to transfert a single frame.
>> 1280x1024 24bits: ~95ms
>>
>> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
>> ---
> 
> I assume that the alpha channel is unused on this display HW and is just
> exposed to user-space to make the DRM driver more compatible ?

Yes, alpha channel is dropped by the hardware, and has no impact on the 
display.
Most userspace now prefer 32bit framebuffer. I know Gnome/wayland 
default to 32bit, and probably other DE are doing the same.

> 
> If so, probably has to be mentioned in the changelog but other than that:

ok I will add this in the commit message.

> 
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> 

Thanks,

-- 

Jocelyn