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

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Gerd Hoffmann <kraxel@redhat.com>, Daniel Vetter <daniel@ffwll.ch>
Cc: airlied@linux.ie, puck.chen@hisilicon.com,
	dri-devel@lists.freedesktop.org,
	virtualization@lists.linux-foundation.org,
	z.liuxinliang@hisilicon.com, hdegoede@redhat.com,
	kong.kongxinwei@hisilicon.com, ray.huang@amd.com,
	zourongrong@gmail.com, sam@ravnborg.org,
	christian.koenig@amd.com
Subject: Re: [PATCH 1/2] drm: Add drm_gem_vram_{pin/unpin}_reserved() and convert mgag200
Date: Tue, 21 May 2019 12:57:02 +0200	[thread overview]
Message-ID: <e9841344-ea79-0904-4ca7-638687cdb66d@suse.de> (raw)
In-Reply-To: <20190521103546.ehrrboraeoe2e6fh@sirius.home.kraxel.org>

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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.
> 
> Thomas, as you have test hardware, can you look into this?

Sure, that's the plan. May take a few days, though.

I'd like to see all of the locking/reservation gone from the helper API.
By using bochs' PRIME helpers, the generic console could probably be
used in mgag200 and ast. That would remove the remaining calls from
mgag200 and ast.

Best regards
Thomas

> thanks,
>   Gerd
> 
> _______________________________________________
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> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

-- 
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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