Re: [PATCH 1/2] drm: Add drm_gem_vram_{pin/unpin}_reserved() and convert mgag200

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 21.05.19 um 12:35 schrieb Gerd Hoffmann:
>   Hi,
> 
>> I think would be good to have a lockdep_assert_held here for the ww_mutex.
>>
>> Also general thing: _reserved is kinda ttm lingo, for dma-buf reservations
>> we call the structure tracking the fences+lock the "reservation", but the
>> naming scheme used is _lock/_unlock.
>>
>> I think would be good to be consistent with that, and use _locked here.
>> Especially for a very simplified vram helper like this one I expect that's
>> going to lead to less wtf moments by driver writers :-)
>>
>> Maybe we should also do a large-scale s/reserve/lock/ within ttm, to align
>> more with what we now have in dma-buf.
> 
> Given that mgag200 is the only user I think the best way forward is to
> improve the mgag200 cursor handling so we can just drop the _reserved
> variants ...
> 
> When looking at mga_crtc_cursor_set() I suspect the easierst way to do
> that would be to simply pin the cursor bo's at driver_load time, then we
> don't have to bother with pinning in mga_crtc_cursor_set() at all.

I've been thinking about converting ast and mgag200 to atomic mode
setting. For that, universal planes would be required. But this seems
incompatible with HW cursors.

With universal planes, cursor planes would probably have to be exported
as RGBA8 framebuffer, but the HW uses MMIO region and 16-color palette.
So there's got to be a translation step and a way of notifying userspace
if the palette overflows. In the current driver code,
drm_crtc_funcs.set_cursor() does this.

How is this done with universal planes? I know that there's
drm_framebuffer_funcs.dirty(), but it doesn't seem to be used much.

Best regards
Thomas


> Thomas, as you have test hardware, can you look into this?
> 
> thanks,
>   Gerd
> 
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-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)


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