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    SubjectRe: [PATCH v5 03/11] scsi: ufs: qcom: Remove unnecessary mb() after writing testbus config
    On Fri, Mar 29, 2024 at 03:46:45PM -0500, Andrew Halaney wrote:
    > Currently, the testbus configuration is written and completed with an
    > mb().
    >
    > mb() ensure 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
    >
    > But, there's really no reason to even ensure completion before
    > continuing. The only requirement here is that this write is ordered to
    > this endpoint (which readl()/writel() guarantees already). For that
    > reason the mb() can be dropped altogether without anything forcing
    > completion.
    >
    > Fixes: 9c46b8676271 ("scsi: ufs-qcom: dump additional testbus registers")
    > Signed-off-by: Andrew Halaney <ahalaney@redhat.com>

    Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

    - Mani

    > ---
    > drivers/ufs/host/ufs-qcom.c | 5 -----
    > 1 file changed, 5 deletions(-)
    >
    > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
    > index 804dc8153e7b..649fada24345 100644
    > --- a/drivers/ufs/host/ufs-qcom.c
    > +++ b/drivers/ufs/host/ufs-qcom.c
    > @@ -1445,11 +1445,6 @@ int ufs_qcom_testbus_config(struct ufs_qcom_host *host)
    > (u32)host->testbus.select_minor << offset,
    > reg);
    > ufs_qcom_enable_test_bus(host);
    > - /*
    > - * Make sure the test bus configuration is
    > - * committed before returning.
    > - */
    > - mb();
    >
    > return 0;
    > }
    >
    > --
    > 2.44.0
    >
    >

    --
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