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Sam Protsenko 8396c793ff mmc: dw_mmc: Fix IDMAC operation with pages bigger than 4K 
Commit 616f876617 ("mmc: pass queue_limits to blk_mq_alloc_disk") [1]
revealed the long living issue in dw_mmc.c driver, existing since the
time when it was first introduced in commit f95f3850f7 ("mmc: dw_mmc:
Add Synopsys DesignWare mmc host driver."), also making kernel boot
broken on platforms using dw_mmc driver with 16K or 64K pages enabled,
with this message in dmesg:

    mmcblk: probe of mmc0:0001 failed with error -22

That's happening because mmc_blk_probe() fails when it calls
blk_validate_limits() consequently, which returns the error due to
failed max_segment_size check in this code:

    /*
     * The maximum segment size has an odd historic 64k default that
     * drivers probably should override.  Just like the I/O size we
     * require drivers to at least handle a full page per segment.
     */
    ...
    if (WARN_ON_ONCE(lim->max_segment_size < PAGE_SIZE))
        return -EINVAL;

In case when IDMAC (Internal DMA Controller) is used, dw_mmc.c always
sets .max_seg_size to 4 KiB:

    mmc->max_seg_size = 0x1000;

The comment in the code above explains why it's incorrect. Arnd
suggested setting .max_seg_size to .max_req_size to fix it, which is
also what some other drivers are doing:

   $ grep -rl 'max_seg_size.*=.*max_req_size' drivers/mmc/host/ | \
     wc -l
   18

This change is not only fixing the boot with 16K/64K pages, but also
leads to a better MMC performance. The linear write performance was
tested on E850-96 board (eMMC only), before commit [1] (where it's
possible to boot with 16K/64K pages without this fix, to be able to do
a comparison). It was tested with this command:

    # dd if=/dev/zero of=somefile bs=1M count=500 oflag=sync

Test results are as follows:

  - 4K pages,  .max_seg_size = 4 KiB:                   94.2 MB/s
  - 4K pages,  .max_seg_size = .max_req_size = 512 KiB: 96.9 MB/s
  - 16K pages, .max_seg_size = 4 KiB:                   126 MB/s
  - 16K pages, .max_seg_size = .max_req_size = 2 MiB:   128 MB/s
  - 64K pages, .max_seg_size = 4 KiB:                   138 MB/s
  - 64K pages, .max_seg_size = .max_req_size = 8 MiB:   138 MB/s

Unfortunately, SD card controller is not enabled in E850-96 yet, so it
wasn't possible for me to run the test on some cheap SD cards to check
this patch's impact on those. But it's possible that this change might
also reduce the writes count, thus improving SD/eMMC longevity.

All credit for the analysis and the suggested solution goes to Arnd.

[1] https://lore.kernel.org/all/20240215070300.2200308-18-hch@lst.de/

Fixes: f95f3850f7 ("mmc: dw_mmc: Add Synopsys DesignWare mmc host driver.")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/all/CA+G9fYtddf2Fd3be+YShHP6CmSDNcn0ptW8qg+stUKW+Cn0rjQ@mail.gmail.com/
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240306232052.21317-1-semen.protsenko@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
2024-08-28 17:20:40 +02:00
arch s390 updates for 6.11-rc5 2024-08-25 12:05:23 +12:00
block block: Read max write zeroes once for __blkdev_issue_write_zeroes() 2024-08-19 09:48:59 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation workqueue: Fixes for v6.11-rc4 2024-08-24 10:35:57 +08:00
drivers mmc: dw_mmc: Fix IDMAC operation with pages bigger than 4K 2024-08-28 17:20:40 +02:00
fs bcachefs fixes for 6.11-rc5, v2 2024-08-25 17:20:48 +12:00
include SCSI fixes on 20240824 2024-08-25 12:00:16 +12:00
init Rust fixes for v6.11 2024-08-16 11:24:06 -07:00
io_uring io_uring/kbuf: sanitize peek buffer setup 2024-08-21 07:16:38 -06:00
ipc sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
kernel cgroup: Fixes for v6.11-rc4 2024-08-24 10:39:18 +08:00
lib bcachefs fixes for 6.11-rc4 2024-08-17 09:46:10 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 16 hotfixes. All except one are for MM. 10 of these are cc:stable and 2024-08-17 19:50:16 -07:00
net NFS Client Bugfixes for Linux 6.11-rc 2024-08-24 09:03:25 +08:00
rust Rust fixes for v6.11 2024-08-16 11:24:06 -07:00
samples treewide: remove unnecessary <linux/version.h> inclusion 2024-08-12 18:36:44 +09:00
scripts Kbuild fixes for v6.11 (2nd) 2024-08-23 07:43:15 +08:00
security KEYS: trusted: dcp: fix leak of blob encryption key 2024-08-15 22:01:14 +03:00
sound Kbuild fixes for v6.11 (2nd) 2024-08-23 07:43:15 +08:00
tools Including fixes from bluetooth and netfilter. 2024-08-23 07:47:01 +08:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX) 2024-08-14 12:28:24 -04:00
.clang-format Docs: Move clang-format from process/ to dev-tools/ 2024-06-26 16:36:00 -06:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: add script and target to generate pacman package 2024-07-22 01:24:22 +09:00
.mailmap mailmap: update entry for David Heidelberg 2024-08-07 18:33:56 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS tracing: Update of MAINTAINERS and CREDITS file 2024-07-18 14:08:42 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS SCSI fixes on 20240824 2024-08-25 12:00:16 +12:00
Makefile Linux 6.11-rc5 2024-08-25 19:07:11 +12:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.