On Fri, Mar 29, 2024 at 03:46:46PM -0500, Andrew Halaney wrote: > Currently, the QUNIPRO_SEL bit is written to and then an mb() is used to > ensure that completes before continuing. > > 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: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations") > Signed-off-by: Andrew Halaney <ahalaney@xxxxxxxxxx> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> - Mani > --- > drivers/ufs/host/ufs-qcom.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c > index 649fada24345..66a6c95f5d72 100644 > --- a/drivers/ufs/host/ufs-qcom.c > +++ b/drivers/ufs/host/ufs-qcom.c > @@ -278,9 +278,6 @@ static void ufs_qcom_select_unipro_mode(struct ufs_qcom_host *host) > > if (host->hw_ver.major >= 0x05) > ufshcd_rmwl(host->hba, QUNIPRO_G4_SEL, 0, REG_UFS_CFG0); > - > - /* make sure above configuration is applied before we return */ > - mb(); > } > > /* > > -- > 2.44.0 > > -- மணிவண்ணன் சதாசிவம்
