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SubjectRe: [PATCH v1 1/2] scsi: ufs: Introduce device quirk "DELAY_AFTER_LPM"
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.teng@mediatek.com>
> Signed-off-by: Peter Wang <peter.wang@mediatek.com>
> Signed-off-by: Stanley Chu <stanley.chu@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)

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