linux-kernel - Re: [PATCH 2/4] drm/ttm: introduce dma cache sync helpers

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Message-ID: <CAAVeFuKCx677Uxcu3XNLkU+er-GBAxqdj_hUDUXHwUN+CS5EsA@mail.gmail.com>
Date:	Fri, 23 May 2014 14:49:40 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	David Airlie <airlied@...ux.ie>,
	Ben Skeggs <bskeggs@...hat.com>, Lucas Stach <dev@...xeye.de>,
	"nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] drm/ttm: introduce dma cache sync helpers

On Mon, May 19, 2014 at 5:33 PM, Thierry Reding
<thierry.reding@...il.com> wrote:
> On Mon, May 19, 2014 at 04:10:56PM +0900, Alexandre Courbot wrote:
>> From: Lucas Stach <dev@...xeye.de>
>>
>> On arches with non-coherent PCI,
>
> I guess since this applies to gk20a
>
>> we need to flush caches ourselfes at
>
> "ourselves". Or perhaps even reword to something like: "..., caches need
> to be flushed and invalidated explicitly", since dma_sync_for_cpu() does
> invalidate rather than flush.

Rephrased as "On arches for which access to GPU memory is non-coherent, caches
need to be flushed and invalidated explicitly at the appropriate places."

>
>> the appropriate places. Introduce two small helpers to make things easy
>> for TTM based drivers.
>>
>> Signed-off-by: Lucas Stach <dev@...xeye.de>
>> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
>> ---
>>  drivers/gpu/drm/ttm/ttm_tt.c    | 25 +++++++++++++++++++++++++
>>  include/drm/ttm/ttm_bo_driver.h | 28 ++++++++++++++++++++++++++++
>>  2 files changed, 53 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> [...]
>> +void ttm_dma_tt_cache_sync_for_device(struct ttm_dma_tt *ttm_dma,
>> +                                   struct device *dev)
>> +{
>> +     int i;
>
> This should probably be unsigned long to match the type of
> ttm_dma->ttm.num_pages.

Fixed.

Thanks,
Alex.
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