Re: [PATCH v1 1/2] scsi: ufs: Introduce device quirk "DELAY_AFTER_LPM"

[Can Guo]

Hi Stanley,

On 2020-07-29 13:18, Stanley Chu wrote:

Some UFS devices require delay after VCC power rail is turned-off.
Introduce a device quirk "DELAY_AFTER_LPM" to add 5ms delays after
VCC power-off during suspend flow.

Just curious, I can understand if you want to add some delays before
turnning off VCC/VCCQ/VCCQ2, but what is the delay AFTER turnning
them off for? I mean the power has been cut by host from PMIC, how
can the delay benefit the UFS device?

Thanks,

Can Guo.

Signed-off-by: Andy Teng <andy.t...@mediatek.com>
Signed-off-by: Peter Wang <peter.w...@mediatek.com>
Signed-off-by: Stanley Chu <stanley....@mediatek.com>
---
 drivers/scsi/ufs/ufs_quirks.h |  7 +++++++
 drivers/scsi/ufs/ufshcd.c     | 11 +++++++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/scsi/ufs/ufs_quirks.h b/drivers/scsi/ufs/ufs_quirks.h

index 2a0041493e30..07f559ac5883 100644
--- a/drivers/scsi/ufs/ufs_quirks.h
+++ b/drivers/scsi/ufs/ufs_quirks.h
@@ -109,4 +109,11 @@ struct ufs_dev_fix {
  */
 #define UFS_DEVICE_QUIRK_SUPPORT_EXTENDED_FEATURES (1 << 10)

+/*
+ * Some UFS devices require delay after VCC power rail is turned-off.

+ * Enable this quirk to introduce 5ms delays after VCC power-off during

+ * suspend flow.
+ */
+#define UFS_DEVICE_QUIRK_DELAY_AFTER_LPM        (1 << 11)
+
 #endif /* UFS_QUIRKS_H_ */
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index acba2271c5d3..63f4e2f75aa1 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -8111,6 +8111,8 @@ static int ufshcd_link_state_transition(struct
ufs_hba *hba,

 static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)
 {
+       bool vcc_off = false;
+
        /*
         * It seems some UFS devices may keep drawing more than sleep current
         * (atleast for 500us) from UFS rails (especially from VCCQ rail).

@@ -8139,13 +8141,22 @@ static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)

        if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba) &&
            !hba->dev_info.is_lu_power_on_wp) {
                ufshcd_setup_vreg(hba, false);
+               vcc_off = true;
        } else if (!ufshcd_is_ufs_dev_active(hba)) {
                ufshcd_toggle_vreg(hba->dev, hba->vreg_info.vcc, false);
+               vcc_off = true;
                if (!ufshcd_is_link_active(hba)) {
                        ufshcd_config_vreg_lpm(hba, hba->vreg_info.vccq);
                        ufshcd_config_vreg_lpm(hba, hba->vreg_info.vccq2);
                }
        }
+
+       /*
+        * Some UFS devices require delay after VCC power rail is turned-off.
+        */
+       if (vcc_off && hba->vreg_info.vcc &&
+               hba->dev_quirks & UFS_DEVICE_QUIRK_DELAY_AFTER_LPM)
+               usleep_range(5000, 5100);
 }

 static int ufshcd_vreg_set_hpm(struct ufs_hba *hba)