Re: [PATCH v1 1/2] scsi: ufs: add required delay after gating reference clock

Can Guo
2020-02-17T12:58:24Z

On 2020-02-17 17:35, Stanley Chu wrote:
> In UFS version 3.0, a newly added attribute bRefClkGatingWaitTime
> defines
> the minimum time for which the reference clock is required by device
> during
> transition to LS-MODE or HIBERN8 state.
>
> Currently this time is detected and stored in
> hba->dev_info.clk_gating_wait_us but applied to vendor implementatios
> only.
> Make it applied to reference clock named as "ref_clk" in device tree in
> common path.
>
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> ---
> drivers/scsi/ufs/ufshcd.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 744b8254220c..7f60721f54d1 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -7417,8 +7417,10 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> *hba, bool on,
> struct ufs_clk_info *clki;
> struct list_head *head = &hba->clk_list_head;
> unsigned long flags;
> + unsigned long wait_us;
> ktime_t start = ktime_get();
> bool clk_state_changed = false;
> + bool ref_clk;
>
> if (list_empty(head))
> goto out;
> @@ -7436,7 +7438,8 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> *hba, bool on,
>
> list_for_each_entry(clki, head, list) {
> if (!IS_ERR_OR_NULL(clki->clk)) {
> - if (skip_ref_clk && !strcmp(clki->name, "ref_clk"))
> + ref_clk = !strcmp(clki->name, "ref_clk") ? true : false;
> + if (skip_ref_clk && ref_clk)
> continue;
>
> clk_state_changed = on ^ clki->enabled;
> @@ -7449,6 +7452,9 @@ static int __ufshcd_setup_clocks(struct ufs_hba
> *hba, bool on,
> }
> } else if (!on && clki->enabled) {
> clk_disable_unprepare(clki->clk);
> + wait_us = hba->dev_info.clk_gating_wait_us;
> + if (ref_clk && wait_us)
> + usleep_range(wait_us, wait_us + 10);

Hi Stanley,

If wait_us is 1us, it would be inappropriate to use usleep_range() here.
You have checks of the delay in patch #2, but why it is not needed here?

Thanks,
Can Guo.

> }
> clki->enabled = on;
> dev_dbg(hba->dev, "%s: clk: %s %sabled\n", __func__,