Re: [PATCH v4 3/4] drm/shmem-helpers: Allocate wc pages on x86

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
	"David Airlie" <airlied@linux.ie>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH v4 3/4] drm/shmem-helpers: Allocate wc pages on x86
Date: Thu, 5 Aug 2021 20:40:07 +0200	[thread overview]
Message-ID: <ea741e89-6ed0-fe7d-6462-7ca01b14c4b9@suse.de> (raw)
In-Reply-To: <YPpxh0QhILXESykX@phenom.ffwll.local>

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Hi

Am 23.07.21 um 09:36 schrieb Daniel Vetter:
> 
> The real fix is to get at the architecture-specific wc allocator, which is
> currently not something that's exposed, but hidden within the dma api. I
> think having this stick out like this is better than hiding it behind fake
> generic code (like we do with drm_clflush, which defacto also only really
> works on x86).
> 
> Also note that ttm has the exact same ifdef in its page allocator, but it
> does fall back to using dma_alloc_coherent on other platforms.

If this fixes a real problem and there's no full solution yet, let's 
take what we have. So if you can extract the essence of this comment 
into a TODO comment that tells how to fix the issue, fell free to add my

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

Best regards
Thomas

> -Daniel
> 
>> Best regard
>> Thomas
>>
>>> +
>>>    	shmem->pages = pages;
>>>    	return 0;
>>> @@ -203,6 +212,11 @@ static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>>>    	if (--shmem->pages_use_count > 0)
>>>    		return;
>>> +#ifdef CONFIG_X86
>>> +	if (shmem->map_wc)
>>> +		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
>>> +#endif
>>> +
>>>    	drm_gem_put_pages(obj, shmem->pages,
>>>    			  shmem->pages_mark_dirty_on_put,
>>>    			  shmem->pages_mark_accessed_on_put);
>>>
>>
>> -- 
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Felix Imendörffer
>>
> 
> 
> 
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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