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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id c35sm2912426pgl.72.2019.08.15.16.15.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 15 Aug 2019 16:15:45 -0700 (PDT) Date: Thu, 15 Aug 2019 16:16:46 -0700 From: Nicolin Chen To: Adrian Hunter Cc: ulf.hansson@linaro.org, thierry.reding@gmail.com, jonathanh@nvidia.com, linux-mmc@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, vdumpa@nvidia.com Subject: Re: [PATCH v2] mmc: tegra: Implement enable_dma() to set dma_mask Message-ID: <20190815231646.GA15635@Asurada-Nvidia.nvidia.com> References: <20190814005741.13331-1-nicoleotsuka@gmail.com> <09d9ba41-f4cd-e515-cd2d-0b4134648059@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <09d9ba41-f4cd-e515-cd2d-0b4134648059@intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 15, 2019 at 02:48:20PM +0300, Adrian Hunter wrote: > On 14/08/19 3:57 AM, Nicolin Chen wrote: > > [ Integrated the change and commit message made by Thierry Reding ] > > > > The SDHCI controller found in early Tegra SoCs (from Tegra20 through > > Tegra114) used an AHB interface to the memory controller, which allowed > > only 32 bits of memory to be addressed. > > > > Starting with Tegra124, this limitation was removed by making the SDHCI > > controllers native MCCIF clients, which means that they got increased > > bandwidth and better arbitration to the memory controller as well as an > > address range extended to 40 bits, out of which only 34 were actually > > used (bits 34-39 are tied to 0 in the controller). > > > > For Tegra186, all of the 40 bits can be used; For Tegra194, 39-bit can > > be used. > > > > So far, sdhci-tegra driver has been relying on sdhci core to configure > > the DMA_BIT_MASK between 32-bit or 64-bit, using one of quirks2 flags: > > SDHCI_QUIRK2_BROKEN_64_BIT_DMA. However, there is a common way, being > > mentioned in sdhci.c file, to set dma_mask via enable_dma() callback in > > the device driver directly. > > > > So this patch implements an enable_dma() callback in the sdhci-tegra, > > in order to set an accurate DMA_BIT_MASK, other than just 32/64 bits. > > Is there a reason this cannot be done at probe time? It's supposed to be done at probe() time. But sdhci_setup_host() does both 32-bit/64-bit dma_mask setting and dma_alloc(), so if the dma_mask isn't correctly set inside sdhci_setup_host(), the allocation would fall to a 64-bit IOVA range that hardware does not support -- smmu error would happen and crash the system. On the other hand, ->enable_dma() is called in that function right after 32-bit/64-bit dma_mask setting. Or is there any other way of adding to probe() that I am missing here? Thanks Nicolin