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[217.229.16.64]) by smtp.gmail.com with ESMTPSA id o5sm703510wmg.25.2019.01.04.02.47.54 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 04 Jan 2019 02:47:54 -0800 (PST) From: Thierry Reding To: Adrian Hunter , Ulf Hansson Cc: Jonathan Hunter , Sowjanya Komatineni , Krishna Reddy , linux-mmc@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] mmc: sdhci: Properly set DMA mask Date: Fri, 4 Jan 2019 11:47:52 +0100 Message-Id: <20190104104753.3383-1-thierry.reding@gmail.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Sender: linux-mmc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Thierry Reding The implementation of sdhci_set_dma_mask() is conflating two things: on one hand it uses the SDHCI_USE_64_BIT_DMA flag to determine whether or not to use the 64-bit addressing capability of the controller and on the other hand it also uses that flag to set a DMA mask for the controller's parent device. However, a controller supporting 64-bit addressing doesn't mean that it needs to support addressing 64 bits of address range. It's perfectly acceptable to use 64-bit addressing for a 32-bit address range or even smaller, even if that makes little sense, considering the extra overhead of the 64-bit addressing descriptors. But it is fairly common for hardware to support somewhere between 32 and 64 bits of address range. Tegra124 and Tegra210, for example, support 34 bits and the newer Tegra186 and Tegra194 support 40 bits. The latter can also use an IOMMU for address translation, which has an input address range of 48 bits. This causes problems with the current algorithm in the SDHCI core for choosing the DMA mask. If the DMA mask is set to 64 bits, the DMA memory allocations can (and usually do because the allocator starts from the top) end up beyond the 40 bit boundary addressable by the SDHCI controller, causing IOMMU faults. For Tegra specifically this problem is currently worked around by setting the SDHCI_QUIRK2_BROKEN_64_BIT_DMA quirk. This causes the DMA mask to always be set to 32 bits and therefore all allocations will fit within the range addressable by the controller. This commit reworks the code in sdhci_set_dma_mask() to fix the above issue. The rationale behind this change is that the SDHCI controller driver should be the authoritative source of the DMA mask setting. The SDHCI core has no way of knowing what the individual SDHCI controllers are capable of. So instead of overriding the DMA mask depending on whether or not 64-bit addressing mode is used, the DMA mask is only modified if absolutely necessary. On one hand, if the controller can only address 32 bits of memory or less, we disable use of 64-bit addressing mode because it is not needed. On the other hand, we also want to make sure that if we don't support 64-bit addressing mode, such as in the case where the BROKEN_64_BIT_DMA quirk is set, we do restrict the DMA mask to fit the capabilities. The latter is an inconsistency by the driver, so we warn about it to make sure it will be addressed in the driver. Signed-off-by: Thierry Reding --- drivers/mmc/host/sdhci.c | 36 ++++++++++++++++++++++-------------- 1 file changed, 22 insertions(+), 14 deletions(-) diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 7c6c93e85b7e..01f81e96be23 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -3499,27 +3499,35 @@ static int sdhci_set_dma_mask(struct sdhci_host *host) { struct mmc_host *mmc = host->mmc; struct device *dev = mmc_dev(mmc); - int ret = -EINVAL; + u64 dma_mask = dma_get_mask(dev); + u64 dma32 = DMA_BIT_MASK(32); + int ret = 0; if (host->quirks2 & SDHCI_QUIRK2_BROKEN_64_BIT_DMA) host->flags &= ~SDHCI_USE_64_BIT_DMA; - /* Try 64-bit mask if hardware is capable of it */ - if (host->flags & SDHCI_USE_64_BIT_DMA) { - ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); - if (ret) { - pr_warn("%s: Failed to set 64-bit DMA mask.\n", - mmc_hostname(mmc)); - host->flags &= ~SDHCI_USE_64_BIT_DMA; - } + /* + * Hardware that can't address more than the 32-bit address range does + * not need to use 64-bit addressing mode, even if it supports it. + */ + if ((host->flags & SDHCI_USE_64_BIT_DMA) && (dma_mask <= dma32)) { + pr_debug("%s: controller needs addresses <= 32-bits\n", + mmc_hostname(mmc)); + host->flags &= ~SDHCI_USE_64_BIT_DMA; } - /* 32-bit mask as default & fallback */ - if (ret) { - ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); + /* + * If the hardware doesn't support 64-bit addressing, make sure to + * restrict the DMA mask so we don't get buffers allocated beyond the + * 32-bit boundary. + */ + if (!(host->flags & SDHCI_USE_64_BIT_DMA) && (dma_mask > dma32)) { + WARN(1, "64-bit DMA not supported, DMA mask %llx\n", dma_mask); + + ret = dma_set_mask_and_coherent(dev, dma32); if (ret) - pr_warn("%s: Failed to set 32-bit DMA mask.\n", - mmc_hostname(mmc)); + pr_warn("%s: failed to set 32-bit DMA mask: %d\n", + mmc_hostname(mmc), ret); } return ret;