linux-kernel - Re: [PATCH v2 04/10] drm/nouveau/fb: add GK20A support

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Message-ID: <CAAVeFuKscuN-=HJOarbzFkG1ARq6-Nfc2pf1ibam9b61Cjbs6Q@mail.gmail.com>
Date:	Wed, 23 Apr 2014 15:11:01 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Ben Skeggs <bskeggs@...hat.com>,
	"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@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 04/10] drm/nouveau/fb: add GK20A support

On Wed, Apr 23, 2014 at 11:07 AM, Alexandre Courbot <acourbot@...dia.com> wrote:
> On 04/22/2014 07:40 PM, Thierry Reding wrote:
>>
>> * PGP Signed by an unknown key
>>
>>
>> On Mon, Apr 21, 2014 at 03:02:16PM +0900, Alexandre Courbot wrote:
>> [...]
>>>
>>> diff --git a/drivers/gpu/drm/nouveau/core/subdev/fb/ramgk20a.c
>>> b/drivers/gpu/drm/nouveau/core/subdev/fb/ramgk20a.c
>>
>> [...]
>>>
>>> +               pages = dma_alloc_from_contiguous(dev, ncmin, order);
>>> +               if (!pages) {
>>> +                       gk20a_ram_put(pfb, &mem);
>>> +                       return -ENOMEM;
>>> +               }
>>> +
>>> +               dma_addr = pfn_to_dma(nv_device_base(nv_device(pfb)),
>>> +                                     page_to_pfn(pages));
>>
>>
>> This breaks compilation on x86 because neither pfn_to_dma() nor
>> dma_to_pfn() are available. Is there some other way this can be
>> allocated so that these functions don't need to be called?
>
>
> Mmm, this is bad. There is probably another more portable way to do this.
> Let me look for it.

page_to_phys()/phys_to_page() can be used by drivers and will work
just fine here since the CPU and GPU use the same physical addresses
to access memory.

Thanks,
Alex.
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