Thread (14 messages) 14 messages, 3 authors, 2020-02-20

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

From: Can Guo <hidden>
Date: 2020-02-17 12:58:24
Also in: linux-mediatek, linux-scsi, lkml

On 2020-02-17 17:35, Stanley Chu wrote:
quoted hunk ↗ jump to hunk
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 <redacted>
---
 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__,
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