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Thu, 27 Aug 2020 08:45:03 -0700 (PDT) Date: Thu, 27 Aug 2020 17:45:02 +0200 From: Thierry Reding To: Robin Murphy Cc: hch@lst.de, joro@8bytes.org, linux@armlinux.org.uk, will@kernel.org, inki.dae@samsung.com, sw0312.kim@samsung.com, kyungmin.park@samsung.com, m.szyprowski@samsung.com, agross@kernel.org, bjorn.andersson@linaro.org, jonathanh@nvidia.com, vdumpa@nvidia.com, digetx@gmail.com, matthias.bgg@gmail.com, yong.wu@mediatek.com, geert+renesas@glider.be, magnus.damm@gmail.com, t-kristo@ti.com, s-anna@ti.com, laurent.pinchart@ideasonboard.com, linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-samsung-soc@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mediatek@lists.infradead.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/18] iommu/tegra: Add IOMMU_DOMAIN_DMA support Message-ID: <20200827154502.GA1660457@ulmo> References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="YiEDa0DAkWCtVeE4" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org --YiEDa0DAkWCtVeE4 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Aug 20, 2020 at 04:08:32PM +0100, Robin Murphy wrote: > Now that arch/arm is wired up for default domains and iommu-dma, > implement the corresponding driver-side support for DMA domains. >=20 > Signed-off-by: Robin Murphy > --- > drivers/iommu/tegra-smmu.c | 37 +++++++++++++++++++++---------------- > 1 file changed, 21 insertions(+), 16 deletions(-) We can't do that yet because it will currently still break for use-cases such as display where we don't properly set up identity mappings during boot. The result is that the dma-iommu code will enable translations before the driver gets a chance to set up any mappings and if the display controller was left on by the bootloader, scanning out a splash screen, this causes faults between the point where dma-iommu is being set up for the display controller and where the display controller starts mapping its own buffers (rather than the ones mapped by the bootloader). That said, I do have a series that I've been carrying around for longer than I've wanted that does exactly this for Tegra SMMU and I'd prefer if you could drop this particular change from your series so that I can keep working on resolving the identity mapping issues first. 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