[PATCH] drm/mgag200: Increase bandwidth for G200se A rev1

[Jocelyn Falempe]

On 25/07/2023 23:31, Roger Sewell wrote:
> 
> Thomas,
> 
> Thank you for your reply.
> 
>>> Table 10 in the following document says that  1440x900 at 60Hz is
>>> supported:
>>> https://www.intel.com/content/dam/support/us/en/documents/motherboards/server/s5520ur/sb/e44031012_s5520ur_s5520urt_tps_r1_9.pdf
>>
>> That manual says that the resolution is only supported with at most
>> 24-bit colors. The old X code still supports that to some extend, but
>> modern userspace doesn't.
> 
> How can I check for sure whether I am using 24 or 32 bits per pixel ?

The easiest solution if you already rebuilt your kernel is to print the 
variable bpp here:

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/mgag200/mgag200_mode.c#L326

pr_info("mgag200 bpp %d\n", bpp);

Also if you can run Wayland at 1440x900 at 60, that would mean the hardware 
is indeed able to handle it in 32bit.

> 
>>> so in particular the chip is said to be a G200e, not the G200SE-A
>>> that the kernel module seems to be interpreting it as.
> 
>> It actually is the G200SE-A. It's just named differently by lspci. The
>> PCI device id should be 0x0522.
> 
> It is indeed 0x0522.
> 
>> So the old kernel already did the right thing.
> 
> (but if I understand the situation right Xorg didn't ?)
> 
>> You can do
>>
>>    cat /sys/class/drm/card1-VGA-1/modes
>>
>> on the old and new kernel. With a monitor connector, it will tell you
>> the supported resolutions.
> 
> With the new kernel and the unmodified mgag200 module it tells me that
> 1440x900 is not on the list - but Xorg still lists it under
> Settings->Display (and Wayland doesn't). With the increased bandwidth
> module in place it tells me 1440x900 is on the list. I think this is as
> you expect as far as the kernel rather than Xorg is concerned.
> 
> Thanks,
> Roger.
> 

Best regards,

-- 

Jocelyn