From: Christoph Hellwig <hch@infradead.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
Sowjanya Komatineni <skomatineni@nvidia.com>,
jonathanh@nvidia.com, mkarthik@nvidia.com, smohammed@nvidia.com,
talho@nvidia.com, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org
Subject: Re: [PATCH V11 3/5] i2c: tegra: Add DMA support
Date: Wed, 6 Feb 2019 23:16:33 -0800 [thread overview]
Message-ID: <20190207071633.GA25149@infradead.org> (raw)
In-Reply-To: <5e66803c-b13b-cb00-e2ff-d096a1650612@gmail.com>
On Wed, Feb 06, 2019 at 05:56:02PM +0300, Dmitry Osipenko wrote:
> > We don't have an IOMMU attached to I2C or APBDMA, so this can't happen
> > and even if we had an IOMMU attached, all we care about is the device's
> > DMA address space, which means IOVA space, and that would still be
> > guaranteed to be contiguous, according to the above.
>
> Yes, but doesn't T186+ have IOMMU support for the DMA controller?
Even if it did, why would that matter? The device would only see
IOVA space, the CPU for a normal driver only sees kernel virtual
space.
Forced contiguous space only makes sense when you have access by CPU
physical address, which should not happen for "normal" device drivers.
next prev parent reply other threads:[~2019-02-07 7:16 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-05 8:56 [PATCH V11 1/5] i2c: tegra: sort all the include headers alphabetically Sowjanya Komatineni
2019-02-05 8:56 ` [PATCH V11 2/5] i2c: tegra: add bus clear Master Support Sowjanya Komatineni
2019-02-05 8:56 ` [PATCH V11 3/5] i2c: tegra: Add DMA support Sowjanya Komatineni
2019-02-05 14:26 ` Dmitry Osipenko
2019-02-05 16:41 ` Sowjanya Komatineni
2019-02-05 16:54 ` Dmitry Osipenko
2019-02-06 14:53 ` Thierry Reding
2019-02-06 14:56 ` Dmitry Osipenko
2019-02-06 17:37 ` Dmitry Osipenko
2019-02-06 19:56 ` Sowjanya Komatineni
2019-02-06 20:02 ` Dmitry Osipenko
2019-02-07 7:16 ` Christoph Hellwig [this message]
2019-02-05 8:56 ` [PATCH V11 4/5] i2c: tegra: update transfer timeout Sowjanya Komatineni
2019-02-05 8:56 ` [PATCH V11 5/5] i2c: tegra: add i2c interface timing support Sowjanya Komatineni
2019-02-05 14:28 ` Dmitry Osipenko
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