On Thu, Dec 21, 2023 at 12:25:21PM -0600, 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 > > 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") > Signed-off-by: Andrew Halaney <ahalaney@xxxxxxxxxx> > --- > drivers/ufs/host/ufs-qcom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c > index 6df2ab3b6f23..ab1ff7432d11 100644 > --- a/drivers/ufs/host/ufs-qcom.c > +++ b/drivers/ufs/host/ufs-qcom.c > @@ -280,7 +280,7 @@ static void ufs_qcom_select_unipro_mode(struct ufs_qcom_host *host) > ufshcd_rmwl(host->hba, QUNIPRO_G4_SEL, 0, REG_UFS_CFG0); > > /* make sure above configuration is applied before we return */ > - mb(); > + ufshcd_readl(host->hba, REG_UFS_CFG1); Same comment as patch 03/11. - Mani > } > > /* > > -- > 2.43.0 > -- மணிவண்ணன் சதாசிவம்
