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From arch/arm/include/asm/io.h
#define __iowmb() wmb()
[ ... ]
#define writel(v,c) ({ __iowmb(); writel_relaxed(v,c); })
From Documentation/memory-barriers.txt: "Note that, when using writel(), a
prior wmb() is not needed to guarantee that the cache coherent memory
writes have completed before writing to the MMIO region."
In other words, calling wmb() before writel() is not necessary. Hence
remove the wmb() calls that precede a writel() call. Remove the wmb() calls
that precede a ufshcd_send_command() call since the latter function uses
writel(). Remove the wmb() call from ufshcd_wait_for_dev_cmd() since the
following chain of events guarantees that the CPU will see up-to-date LRB
values:
- UFS controller writes to host memory.
- UFS controller posts completion interrupt after the memory writes from
the previous step are visible to the CPU.
- complete(hba->dev_cmd.complete) is called from the UFS interrupt handler.
- The wait_for_completion(hba->dev_cmd.complete) call in
ufshcd_wait_for_dev_cmd() returns.
Link: https://lore.kernel.org/r/20210722033439.26550-10-bvanassche@acm.org
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Can Guo <cang@codeaurora.org>
Cc: Asutosh Das <asutoshd@codeaurora.org>
Cc: Avri Altman <avri.altman@wdc.com>
Tested-by: Avri altman <avri.altman@wdc.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Daejun Park <daejun7.park@samsung.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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.