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SubjectRE: [PATCH v2 1/5] scsi: ufs-mediatek: Fix imprecise waiting time for ref-clk control
Date

>
> Currently ref-clk control timeout is implemented by Jiffies. However
> jiffies is not accurate enough thus "false timeout" may happen.
>
> Use more accurate delay mechanism instead, for example, ktime.
>
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> Reviewed-by: Andy Teng <andy.teng@mediatek.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>

> ---
> drivers/scsi/ufs/ufs-mediatek.c | 7 ++++---
> drivers/scsi/ufs/ufs-mediatek.h | 2 +-
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
> index d56ce8d97d4e..523ee5573921 100644
> --- a/drivers/scsi/ufs/ufs-mediatek.c
> +++ b/drivers/scsi/ufs/ufs-mediatek.c
> @@ -120,7 +120,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba,
> bool on)
> {
> struct ufs_mtk_host *host = ufshcd_get_variant(hba);
> struct arm_smccc_res res;
> - unsigned long timeout;
> + ktime_t timeout, time_checked;
> u32 value;
>
> if (host->ref_clk_enabled == on)
> @@ -135,8 +135,9 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba,
> bool on)
> }
>
> /* Wait for ack */
> - timeout = jiffies + msecs_to_jiffies(REFCLK_REQ_TIMEOUT_MS);
> + timeout = ktime_add_us(ktime_get(), REFCLK_REQ_TIMEOUT_US);
> do {
> + time_checked = ktime_get();
> value = ufshcd_readl(hba, REG_UFS_REFCLK_CTRL);
>
> /* Wait until ack bit equals to req bit */
> @@ -144,7 +145,7 @@ static int ufs_mtk_setup_ref_clk(struct ufs_hba *hba,
> bool on)
> goto out;
>
> usleep_range(100, 200);
> - } while (time_before(jiffies, timeout));
> + } while (ktime_before(time_checked, timeout));
Nit: you could get rid of time_checked if you would use ktime_compare(ktime_get(), timeout) > 0

Thanks,
Avri

>
> dev_err(hba->dev, "missing ack of refclk req, reg: 0x%x\n", value);
>
> diff --git a/drivers/scsi/ufs/ufs-mediatek.h b/drivers/scsi/ufs/ufs-mediatek.h
> index 5bbd3e9cbae2..fc42dcbfd800 100644
> --- a/drivers/scsi/ufs/ufs-mediatek.h
> +++ b/drivers/scsi/ufs/ufs-mediatek.h
> @@ -28,7 +28,7 @@
> #define REFCLK_REQUEST BIT(0)
> #define REFCLK_ACK BIT(1)
>
> -#define REFCLK_REQ_TIMEOUT_MS 3
> +#define REFCLK_REQ_TIMEOUT_US 3000
>
> /*
> * Vendor specific pre-defined parameters
> --
> 2.18.0

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