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From: Rusty Russell <rusty@rustcorp.com.au>
To: Ohad Ben-Cohen <ohad@wizery.com>,
	Sjur BRENDELAND <sjur.brandeland@stericsson.com>
Cc: Amit Shah <amit.shah@redhat.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>
Subject: Re: Question regarding Virtio Console and Remoteproc
Date: Mon, 04 Jun 2012 14:15:41 +0930	[thread overview]
Message-ID: <87bokz1y8a.fsf@rustcorp.com.au> (raw)
In-Reply-To: <CAK=WgbY9cXByKXEnpSvVr3dCecmKyumAQ6ffX8_2ghsAr2haEQ@mail.gmail.com>

On Fri, 1 Jun 2012 10:51:38 +0300, Ohad Ben-Cohen <ohad@wizery.com> wrote:
> On Fri, Jun 1, 2012 at 10:31 AM, Sjur BRENDELAND
> <sjur.brandeland@stericsson.com> wrote:
> >        if (virtio_has_feature(vdev, VIRTIO_CONSOLE_USE_DMA_MEM)) {
> >                dma_addr_t dma;
> >                buf = dma_alloc_coherent(dev, size, &dma, GFP_KERNEL);
> >        } else
> >                buf = kmalloc(count, GFP_KERNEL);
> 
> Something along those lines is also needed for remote processors which
> access memory via an IOMMU (e.g. OMAP4's M3 and DSP).
> 
> Allocating the memory via the DMA API will seamlessly configure the
> relevant IOMMU as needed, and will make the buffers accessible to the
> remote processors.
> 
> Thanks,
> Ohad.

It seems quite sensible.  The formal definition in the spec would be
good.  In particular, defining DMA_MEM in a generic (non-Linux) way will
be interesting.

Thanks,
Rusty.
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  reply	other threads:[~2012-06-04  4:45 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-01  7:31 Question regarding Virtio Console and Remoteproc Sjur BRENDELAND
2012-06-01  7:51 ` Ohad Ben-Cohen
2012-06-04  4:45   ` Rusty Russell [this message]
2012-06-04  6:10     ` Benjamin Herrenschmidt
2012-06-05  9:43 ` Amit Shah

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