Re: [PATCH v3 5/5] scsi: ufs: Fix possible VCC power drain during runtime suspend

[Asutosh Das (asd)]

Hi Stanley,

On 5/16/2020 10:46 AM, Stanley Chu wrote:
> The commit "scsi: ufs: Fix WriteBooster flush during runtime
> suspend" promises essential resource, i.e., for UFS devices doing
> WriteBooster buffer flush and Auto BKOPs. However if device
> finishes its job but not resumed for a very long time, system
> will have unnecessary power drain because VCC is still supplied.
>
> To fix this, a method to recheck the threshold of keeping VCC
> supply is required. However, the threshold recheck needs to
> re-activate the link because the decision depends on the device
> status.
>
> Introduce a delayed work to force runtime resume after a certain
> delay during runtime suspend. This makes threshold recheck simpler
> which will be done in the next runtime-suspend.
>
> Signed-off-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> ---

Is there a reason to have this code as a separate patch?
[1] Commit: "scsi: ufs: Fix WriteBooster flush during runtime suspend" 
introduces 'keep_curr_dev_pwr_mode' and the very next change (this one) 
removes it.
Do you think this change and [1] should be merged?

>   drivers/scsi/ufs/ufs.h    |  1 +
>   drivers/scsi/ufs/ufshcd.c | 43 ++++++++++++++++++++++++++++++++++-----
>   drivers/scsi/ufs/ufshcd.h |  1 +
>   3 files changed, 40 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h
> index db07eedfed96..c70845d41449 100644
> --- a/drivers/scsi/ufs/ufs.h
> +++ b/drivers/scsi/ufs/ufs.h
> @@ -574,6 +574,7 @@ struct ufs_dev_info {
>   	u32 d_ext_ufs_feature_sup;
>   	u8 b_wb_buffer_type;
>   	u32 d_wb_alloc_units;
> +	bool b_rpm_dev_flush_capable;
>   	u8 b_presrv_uspc_en;
>   };
>   
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index f4f2c7b5ab0a..a137553f9b41 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -94,6 +94,9 @@
>   /* default delay of autosuspend: 2000 ms */
>   #define RPM_AUTOSUSPEND_DELAY_MS 2000
>   
> +/* Default delay of RPM device flush delayed work */
> +#define RPM_DEV_FLUSH_RECHECK_WORK_DELAY_MS 5000
> +
>   /* Default value of wait time before gating device ref clock */
>   #define UFSHCD_REF_CLK_GATING_WAIT_US 0xFF /* microsecs */
>   
> @@ -5310,7 +5313,7 @@ static bool ufshcd_wb_presrv_usrspc_keep_vcc_on(struct ufs_hba *hba,
>   	return false;
>   }
>   
> -static bool ufshcd_wb_keep_vcc_on(struct ufs_hba *hba)
> +static bool ufshcd_wb_need_flush(struct ufs_hba *hba)
>   {
>   	int ret;
>   	u32 avail_buf;
> @@ -5348,6 +5351,21 @@ static bool ufshcd_wb_keep_vcc_on(struct ufs_hba *hba)
>   	return ufshcd_wb_presrv_usrspc_keep_vcc_on(hba, avail_buf);
>   }
>   
> +static void ufshcd_rpm_dev_flush_recheck_work(struct work_struct *work)
> +{
> +	struct ufs_hba *hba = container_of(to_delayed_work(work),
> +					   struct ufs_hba,
> +					   rpm_dev_flush_recheck_work);
> +	/*
> +	 * To prevent unnecessary VCC power drain after device finishes
> +	 * WriteBooster buffer flush or Auto BKOPs, force runtime resume
> +	 * after a certain delay to recheck the threshold by next runtime
> +	 * supsend.
> +	 */
> +	pm_runtime_get_sync(hba->dev);
> +	pm_runtime_put_sync(hba->dev);
> +}
> +
>   /**
>    * ufshcd_exception_event_handler - handle exceptions raised by device
>    * @work: pointer to work data
> @@ -8164,7 +8182,6 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   	enum ufs_pm_level pm_lvl;
>   	enum ufs_dev_pwr_mode req_dev_pwr_mode;
>   	enum uic_link_state req_link_state;
> -	bool keep_curr_dev_pwr_mode = false;
>   
>   	hba->pm_op_in_progress = 1;
>   	if (!ufshcd_is_shutdown_pm(pm_op)) {
> @@ -8224,11 +8241,12 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   		 * Hibern8, keep device power mode as "active power mode"
>   		 * and VCC supply.
>   		 */
> -		keep_curr_dev_pwr_mode = hba->auto_bkops_enabled ||
> +		hba->dev_info.b_rpm_dev_flush_capable =
> +			hba->auto_bkops_enabled ||
>   			(((req_link_state == UIC_LINK_HIBERN8_STATE) ||
>   			((req_link_state == UIC_LINK_ACTIVE_STATE) &&
>   			ufshcd_is_auto_hibern8_enabled(hba))) &&
> -			ufshcd_wb_keep_vcc_on(hba));
> +			ufshcd_wb_need_flush(hba));
>   	}
>   
>   	if (req_dev_pwr_mode != hba->curr_dev_pwr_mode) {
> @@ -8238,7 +8256,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   			ufshcd_disable_auto_bkops(hba);
>   		}
>   
> -		if (!keep_curr_dev_pwr_mode) {
> +		if (!hba->dev_info.b_rpm_dev_flush_capable) {
>   			ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);
>   			if (ret)
>   				goto enable_gating;
> @@ -8295,9 +8313,16 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   	if (hba->clk_scaling.is_allowed)
>   		ufshcd_resume_clkscaling(hba);
>   	hba->clk_gating.is_suspended = false;
> +	hba->dev_info.b_rpm_dev_flush_capable = false;
>   	ufshcd_release(hba);
>   out:
> +	if (hba->dev_info.b_rpm_dev_flush_capable) {
> +		schedule_delayed_work(&hba->rpm_dev_flush_recheck_work,
> +			msecs_to_jiffies(RPM_DEV_FLUSH_RECHECK_WORK_DELAY_MS));
> +	}
> +
>   	hba->pm_op_in_progress = 0;
> +
Nitpick; newline, perhaps?

>   	if (ret)
>   		ufshcd_update_reg_hist(&hba->ufs_stats.suspend_err, (u32)ret);
>   	return ret;
> @@ -8386,6 +8411,11 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   	/* Enable Auto-Hibernate if configured */
>   	ufshcd_auto_hibern8_enable(hba);
>   
> +	if (hba->dev_info.b_rpm_dev_flush_capable) {
> +		hba->dev_info.b_rpm_dev_flush_capable = false;
> +		cancel_delayed_work(&hba->rpm_dev_flush_recheck_work);
> +	}
> +
>   	/* Schedule clock gating in case of no access to UFS device yet */
>   	ufshcd_release(hba);
>   
> @@ -8859,6 +8889,9 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>   						UFS_SLEEP_PWR_MODE,
>   						UIC_LINK_HIBERN8_STATE);
>   
> +	INIT_DELAYED_WORK(&hba->rpm_dev_flush_recheck_work,
> +			  ufshcd_rpm_dev_flush_recheck_work);
> +
>   	/* Set the default auto-hiberate idle timer value to 150 ms */
>   	if (ufshcd_is_auto_hibern8_supported(hba) && !hba->ahit) {
>   		hba->ahit = FIELD_PREP(UFSHCI_AHIBERN8_TIMER_MASK, 150) |
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> index 8db7a6101892..9acd437037e8 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -745,6 +745,7 @@ struct ufs_hba {
>   	struct request_queue	*bsg_queue;
>   	bool wb_buf_flush_enabled;
>   	bool wb_enabled;
> +	struct delayed_work rpm_dev_flush_recheck_work;
>   };
>   
>   /* Returns true if clocks can be gated. Otherwise false */


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