linux-kernel - [PATCH v3 2/2] scsi: ufs: core: Replace hard coded vcc-off delay with a variable

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Message-ID: <72fa649406a0bf02271575b7d58f22c968aa5d7e.1760383740.git.quic_nguyenb@quicinc.com>
Date: Mon, 13 Oct 2025 12:38:16 -0700
From: "Bao D. Nguyen" <quic_nguyenb@...cinc.com>
To: <quic_cang@...cinc.com>, <quic_nitirawa@...cinc.com>, <bvanassche@....org>,
        <avri.altman@....com>, <peter.wang@...iatek.com>,
        <adrian.hunter@...el.com>, <martin.petersen@...cle.com>
CC: <linux-scsi@...r.kernel.org>, "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley"
	<James.Bottomley@...senPartnership.com>,
        Bean Huo <beanhuo@...ron.com>,
        "Neil
 Armstrong" <neil.armstrong@...aro.org>,
        Eric Biggers <ebiggers@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 2/2] scsi: ufs: core: Replace hard coded vcc-off delay with a variable

After the ufs device vcc is powered off, all the ufs device
manufacturers require a minimum of 1ms of power-off time before
vcc can be powered on again. This requirement has been verified
with all the ufs device manufacturer's datasheets.

Replace the hard coded 5ms delay with a variable with a default
setting of 2ms to improve the system resume latency. The platform
drivers can override this setting as needed.

Signed-off-by: Bao D. Nguyen <quic_nguyenb@...cinc.com>
Reviewed-by: Bart Van Assche <bvanassche@....org>
---
 drivers/ufs/core/ufshcd.c | 10 +++++++++-
 include/ufs/ufshcd.h      |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index e8842dc..8d4cdd5 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -9741,7 +9741,8 @@ static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)
 	 * All UFS devices require delay after VCC power rail is turned-off.
 	 */
 	if (vcc_off && hba->vreg_info.vcc && !hba->vreg_info.vcc->always_on)
-		usleep_range(5000, 5100);
+		usleep_range(hba->vcc_off_delay_us,
+			     hba->vcc_off_delay_us + 100);
 }
 
 #ifdef CONFIG_PM
@@ -10665,6 +10666,13 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 						UFS_SLEEP_PWR_MODE,
 						UIC_LINK_HIBERN8_STATE);
 
+	/*
+	 * Most ufs devices require 1ms delay after vcc is powered off before
+	 * it can be powered on again. Set the default to 2ms. The platform
+	 * drivers can override this setting as needed.
+	 */
+	hba->vcc_off_delay_us = 2000;
+
 	init_completion(&hba->dev_cmd.complete);
 
 	err = ufshcd_hba_init(hba);
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 1d39437..4be32e3 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -1140,6 +1140,8 @@ struct ufs_hba {
 	int critical_health_count;
 	atomic_t dev_lvl_exception_count;
 	u64 dev_lvl_exception_id;
+
+	u32 vcc_off_delay_us;
 };
 
 /**
-- 
2.7.4