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356a8ce7cd
Currently a wmb() is used to ensure that writes to the
UTP_TASK_REQ_LIST_BASE* regs are completed prior to following writes to
the run/stop registers.
wmb() ensures that the write completes, but completion doesn't mean that
it isn't stored in a buffer somewhere. The recommendation for
ensuring the bits have taken effect on the device is to perform a read
back to force it to make it all the way to the device. This is
documented in device-io.rst and a talk by Will Deacon on this can
be seen over here:
https://youtu.be/i6DayghhA8Q?si=MiyxB5cKJXSaoc01&t=1678
But, none of that is necessary here. All of the writel()/readl()'s here
are to the same endpoint, so they will be ordered. There's no subsequent
delay() etc that requires it to have taken effect already, so no
readback is necessary here.
For that reason just drop the wmb() altogether.
Fixes: 897efe628d ("scsi: ufs: add missing memory barriers")
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-11-181252004586@redhat.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.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 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.