Linux Tegra architecture development
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From: Terje Bergstrom <tbergstrom-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
To: Thierry Reding
	<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Cc: linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Debarshi Dutta <ddutta-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: Re: [PATCH] arm64: tegra: Add the GPU on Tegra194
Date: Thu, 16 Jul 2020 08:05:24 -0700	[thread overview]
Message-ID: <4f9cfab5-2a5d-379c-ba17-1aca896b4110@nvidia.com> (raw)
In-Reply-To: <20200716131753.GG535268@ulmo>

On 7/16/2020 6:17 AM, Thierry Reding wrote:
> On Thu, Jul 16, 2020 at 01:59:33PM +0100, Jon Hunter wrote:
>> I also see that for gv11b we populate 'dma-coherent' and so we should
>> probably add this as well.
> Do we know for certain that the GPU is DMA coherent? I've only tested
> this (with local patches to Nouveau) without dma-coherent, so I have not
> actually verified that it works without.
>
> I vaguely recall reading that there are different apertures for sysmem,
> one for coherent sysmem and another for non-coherent sysmem. So I'm not
> sure if dma-coherent here will work without additional code in the
> driver to ensure that all memory is allocated from the coherent sysmem
> aperture.

We do have the choices of coherent and non-coherent memory accesses in 
the iGPU via the two sysmem apertures. But in Tegra194 we're forcing 
coherency from the memory subsystem side, so all accesses are coherent.

Terje

      reply	other threads:[~2020-07-16 15:05 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-16 12:01 [PATCH] arm64: tegra: Add the GPU on Tegra194 Thierry Reding
     [not found] ` <20200716120138.532906-1-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2020-07-16 12:59   ` Jon Hunter
     [not found]     ` <3748e071-4d08-8e77-43f6-de37f5a7eb1e-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2020-07-16 13:17       ` Thierry Reding
2020-07-16 15:05         ` Terje Bergstrom [this message]

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