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

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Date:   Mon, 17 Feb 2020 17:35:58 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     <linux-scsi@...r.kernel.org>, <martin.petersen@...cle.com>,
        <avri.altman@....com>, <alim.akhtar@...sung.com>,
        <jejb@...ux.ibm.com>
CC:     <beanhuo@...ron.com>, <asutoshd@...eaurora.org>,
        <cang@...eaurora.org>, <matthias.bgg@...il.com>,
        <bvanassche@....org>, <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kuohong.wang@...iatek.com>,
        <peter.wang@...iatek.com>, <chun-hung.wu@...iatek.com>,
        <andy.teng@...iatek.com>, Stanley Chu <stanley.chu@...iatek.com>
Subject: [PATCH v1 1/2] scsi: ufs: add required delay after gating reference clock

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@...iatek.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);
 			}
 			clki->enabled = on;
 			dev_dbg(hba->dev, "%s: clk: %s %sabled\n", __func__,
-- 
2.18.0