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| author | Andrew Halaney <ahalaney@redhat.com> | 2024-03-29 23:46:43 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-06-12 12:03:09 +0300 |
| commit | bfda254ceb5bb5984335a662e32ff4ad9492e485 (patch) | |
| tree | 944c339bf0e8b9ae3ace35108b245fd492574542 /drivers/ufs | |
| parent | 90098f0a160709ea2555f7720d3f63658f110b36 (diff) | |
| download | linux-bfda254ceb5bb5984335a662e32ff4ad9492e485.tar.xz | |
scsi: ufs: qcom: Perform read back after writing reset bit
[ Upstream commit c4d28e06b0c94636f6e35d003fa9ebac0a94e1ae ]
Currently, the reset bit for the UFS provided reset controller (used by its
phy) is written to, and then a mb() happens to try and ensure that hit the
device. Immediately afterwards a usleep_range() occurs.
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. By doing so and
guaranteeing the ordering against the immediately following usleep_range(),
the mb() can safely be removed.
Fixes: 81c0fc51b7a7 ("ufs-qcom: add support for Qualcomm Technologies Inc platforms")
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
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-v5-1-181252004586@redhat.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/ufs')
| -rw-r--r-- | drivers/ufs/host/ufs-qcom.h | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/ufs/host/ufs-qcom.h b/drivers/ufs/host/ufs-qcom.h index 44466a395bb5..8a3a65625db5 100644 --- a/drivers/ufs/host/ufs-qcom.h +++ b/drivers/ufs/host/ufs-qcom.h @@ -146,10 +146,10 @@ static inline void ufs_qcom_assert_reset(struct ufs_hba *hba) 1 << OFFSET_UFS_PHY_SOFT_RESET, REG_UFS_CFG1); /* - * Make sure assertion of ufs phy reset is written to - * register before returning + * Dummy read to ensure the write takes effect before doing any sort + * of delay */ - mb(); + ufshcd_readl(hba, REG_UFS_CFG1); } static inline void ufs_qcom_deassert_reset(struct ufs_hba *hba) @@ -158,10 +158,10 @@ static inline void ufs_qcom_deassert_reset(struct ufs_hba *hba) 0 << OFFSET_UFS_PHY_SOFT_RESET, REG_UFS_CFG1); /* - * Make sure de-assertion of ufs phy reset is written to - * register before returning + * Dummy read to ensure the write takes effect before doing any sort + * of delay */ - mb(); + ufshcd_readl(hba, REG_UFS_CFG1); } /* Host controller hardware version: major.minor.step */ |