[PATCH] drm/radeon: Set depth on low mem to 16 bpp instead of 8 bpp

[Alex Deucher]

On Wed, Jul 19, 2017 at 4:45 AM, Takashi Iwai <tiwai at suse.de> wrote:
> On Tue, 18 Jul 2017 22:53:48 +0200,
> Michel D4nzer wrote:
>>
>> On 18/07/17 11:20 AM, Takashi Iwai wrote:
>> > From: Egbert Eich <eich at suse.de>
>> >
>> > The radeon driver reduces the framebuffer resolution to 8bpp if a
>> > device with less than 32MB VRAM is found.  This causes the framebuffer
>> > to run in 8 bit paletted mode.  For a text console this is not an
>> > issue as 256 different colors is more than one gets on a VGA text
>> > console.  However this leads to a poor 8bit pseudo-color visual when
>> > running X on fbdev, too, which is quite ugly.
>> >
>> > In this patch, we try to give some moderate compromise: limit the
>> > framebuffer bpp to 8 only when VRAM is 8MB or less, and use 16 bpp
>> > otherwise for 32MB or less VRAM.
>> >
>> > Signed-off-by: Egbert Eich <eich at suse.de>
>> > Signed-off-by: Takashi Iwai <tiwai at suse.de>
>> > ---
>> >
>> > This has been included in SUSE kernel for quite some time, and I'm
>> > trying to upstream this.  The 16bpp looks more reasonable nowadays,
>> > but I know this is a matter of taste, too.  It'd be great if you guys
>> > can comment on this, at least, whether it's uttly non-sense or not.
>>
>> [...]
>>
>> > diff --git a/drivers/gpu/drm/radeon/radeon_fb.c b/drivers/gpu/drm/radeon/radeon_fb.c
>> > index 356ad90a5238..b5f2642f124b 100644
>> > --- a/drivers/gpu/drm/radeon/radeon_fb.c
>> > +++ b/drivers/gpu/drm/radeon/radeon_fb.c
>> > @@ -347,9 +347,12 @@ int radeon_fbdev_init(struct radeon_device *rdev)
>> >     if (list_empty(&rdev->ddev->mode_config.connector_list))
>> >             return 0;
>> >   - /* select 8 bpp console on RN50 or 16MB cards */
>> > -   if (ASIC_IS_RN50(rdev) || rdev->mc.real_vram_size <= (32*1024*1024))
>> > +   /* select 8 bpp console on 8MB cards, or 16 bpp on RN50 or 32MB */
>> > +   if (rdev->mc.real_vram_size <= (8*1024*1024))
>> >             bpp_sel = 8;
>> > +   else if (ASIC_IS_RN50(rdev) ||
>> > +            rdev->mc.real_vram_size <= (32*1024*1024))
>> > +           bpp_sel = 16;
>> >             rfbdev = kzalloc(sizeof(struct radeon_fbdev), GFP_KERNEL);
>> >     if (!rfbdev)
>> >
>>
>> Looks reasonable to me — if nothing else, at least the comment and
>> code will match again! :)
>>
>> My only potential doubt is whether there could be another reason than
>> VRAM size why RN50 should use 8 bpp. Assuming not,
>
> We also hope there no such popular board :)
> FWIW, at least we didn't get a relevant bug report, so far.
>
>> Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>
>
> Thanks!

Applied.  thanks!

Alex


>
>
> Takashi
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