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

[Takashi Iwai <tiwai-l3A5Bk7waGM@public.gmane.org>]

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@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@suse.de>
> > Signed-off-by: Takashi Iwai <tiwai@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@amd.com>

Thanks!


Takashi
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