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author | Andrew Halaney <ahalaney@redhat.com> | 2024-03-29 23:46:44 +0300 |
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committer | Martin K. Petersen <martin.petersen@oracle.com> | 2024-04-06 04:06:28 +0300 |
commit | a862fafa263aea0f427d51aca6ff7fd9eeaaa8bd (patch) | |
tree | 8bcc3ee186e36d4a0a0140955628bb6cf79a5738 /drivers/ufs/host/cdns-pltfrm.c | |
parent | c4d28e06b0c94636f6e35d003fa9ebac0a94e1ae (diff) | |
download | linux-a862fafa263aea0f427d51aca6ff7fd9eeaaa8bd.tar.xz |
scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US
Currently after writing to REG_UFS_SYS1CLK_1US a mb() is used to ensure
that write has gone through to the device.
mb() ensures that the write completes, but completion doesn't mean that it
isn't stored in a buffer somewhere. The recommendation for ensuring this
bit has 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
Let's do that to ensure the bit hits the device. Because the mb()'s purpose
wasn't to add extra ordering (on top of the ordering guaranteed by
writel()/readl()), it can safely be removed.
Fixes: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations")
Reviewed-by: Can Guo <quic_cang@quicinc.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20240329-ufs-reset-ensure-effect-before-delay-v5-2-181252004586@redhat.com
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/ufs/host/cdns-pltfrm.c')
0 files changed, 0 insertions, 0 deletions