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Nicolin Chen b960bc448a mmc: tegra: Implement ->set_dma_mask() 
The SDHCI controller on Tegra186 supports 40-bit addressing, which is
usually enough to address all of system memory. However, if the SDHCI
controller is behind an IOMMU, the address space can go beyond. This
happens on Tegra186 and later where the ARM SMMU has an input address
space of 48 bits. If the DMA API is backed by this ARM SMMU, the top-
down IOVA allocator will cause IOV addresses to be returned that the
SDHCI controller cannot access.

Unfortunately, prior to the introduction of the ->set_dma_mask() host
operation, the SDHCI core would set either a 64-bit DMA mask if the
controller claimed to support 64-bit addressing, or a 32-bit DMA mask
otherwise.

Since the full 64 bits cannot be addressed on Tegra, this had to be
worked around in commit 68481a7e1c ("mmc: tegra: Mark 64 bit dma
broken on Tegra186") by setting the SDHCI_QUIRK2_BROKEN_64_BIT_DMA
quirk, which effectively restricts the DMA mask to 32 bits.

One disadvantage of this is that dma_map_*() APIs will now try to use
the swiotlb to bounce DMA to addresses beyond of the controller's DMA
mask. This in turn caused degraded performance and can lead to
situations where the swiotlb buffer is exhausted, which in turn leads
to DMA transfers to fail.

With the recent introduction of the ->set_dma_mask() host operation,
this can now be properly fixed. For each generation of Tegra, the exact
supported DMA mask can be configured. This kills two birds with one
stone: it avoids the use of bounce buffers because system memory never
exceeds the addressable memory range of the SDHCI controllers on these
devices, and at the same time when an IOMMU is involved, it prevents
IOV addresses from being allocated beyond the addressible range of the
controllers.

Since the DMA mask is now properly handled, the 64-bit DMA quirk can be
removed.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
[treding@nvidia.com: provide more background in commit message]
Tested-by: Nicolin Chen <nicoleotsuka@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Cc: stable@vger.kernel.org # v4.15 +
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
History 2019-09-27 20:30:13 +02:00
arch Modules updates for v5.4 2019-09-22 10:34:46 -07:00
block dma-mapping updates for 5.4: 2019-09-19 13:27:23 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto - crypto and DM crypt advances that allow the crypto API to reclaim 2019-09-21 10:40:37 -07:00
Documentation RTC for 5.4 2019-09-22 11:05:43 -07:00
drivers mmc: tegra: Implement ->set_dma_mask() 2019-09-27 20:30:13 +02:00
fs Changes for gfs2: 2019-09-21 14:42:59 -07:00
include modules: make MODULE_IMPORT_NS() work even when modular builds are disabled 2019-09-22 11:15:14 -07:00
init Modules updates for v5.4 2019-09-22 10:34:46 -07:00
ipc Merge branch 'work.mount-base' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-09-18 13:15:58 -07:00
kernel Modules updates for v5.4 2019-09-22 10:34:46 -07:00
lib Modules updates for v5.4 2019-09-22 10:34:46 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm hmm related patches for 5.4 2019-09-21 10:07:42 -07:00
net RDMA subsystem updates for 5.4 2019-09-21 10:26:24 -07:00
samples rpmsg updates for v5.4 2019-09-22 10:58:15 -07:00
scripts Modules updates for v5.4 2019-09-22 10:34:46 -07:00
security keys: Fix missing null pointer check in request_key_auth_describe() 2019-09-05 14:19:25 -07:00
sound Main MIPS changes for v5.4: 2019-09-22 09:30:30 -07:00
tools f2fs-for-5.4-rc1 2019-09-21 14:26:33 -07:00
usr kbuild: remove clean-dirs syntax 2019-08-29 23:54:29 +09:00
virt * s390: ioctl hardening, selftests 2019-09-18 09:49:13 -07:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2019-09-18 12:34:53 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS CREDITS: Update email address 2019-09-13 17:21:38 +03:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS power supply and reset changes for the v5.4 series 2019-09-22 12:04:59 -07:00
Makefile Modules updates for v5.4 2019-09-22 10:34:46 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.