Messages in this thread Patch in this message |  | | Date | Fri, 22 Apr 2022 22:03:22 -0700 | Subject | Re: [PATCH 3/5] scsi: ufs: qcom: Add a readl() to make sure ref_clk gets enabled | From | Bart Van Assche <> |
| |
On 4/22/22 06:21, Manivannan Sadhasivam wrote: > In ufs_qcom_dev_ref_clk_ctrl(), it was noted that the ref_clk needs to be > stable for atleast 1us. Eventhough there is wmb() to make sure the write ^ ^ Some spaces are missing.
> gets "completed", there is no guarantee that the write actually reached > the UFS device. There is a good chance that the write could be stored in > a Write Buffer (WB). In that case, eventhough the CPU waits for 1us, the ^ missing space----------------------------
> ref_clk might not be stable for that period. > > So lets do a readl() to make sure that the previous write has reached the > UFS device before udelay(). > > Cc: stable@vger.kernel.org > Fixes: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations") > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > --- > drivers/scsi/ufs/ufs-qcom.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c > index 5f0a8f646eb5..5b9986c63eed 100644 > --- a/drivers/scsi/ufs/ufs-qcom.c > +++ b/drivers/scsi/ufs/ufs-qcom.c > @@ -690,6 +690,12 @@ static void ufs_qcom_dev_ref_clk_ctrl(struct ufs_qcom_host *host, bool enable) > /* ensure that ref_clk is enabled/disabled before we return */ > wmb(); > > + /* > + * Make sure the write to ref_clk reaches the destination and > + * not stored in a Write Buffer (WB). > + */ > + readl(host->dev_ref_clk_ctrl_mmio); > + > /* > * If we call hibern8 exit after this, we need to make sure that > * device ref_clk is stable for at least 1us before the hibern8
The comment above the wmb() call looks wrong to me. How about removing that wmb() call?
Thanks,
Bart.
|  |