Re: [PATCH v1 4/4] scsi: ufs: Fix WriteBooster flush during runtime suspend

["Asutosh Das (asd)" <asutoshd@codeaurora.org>]

On 5/12/2020 3:47 AM, Stanley Chu wrote:
> Currently UFS host driver promises VCC supply if UFS device
> needs to do WriteBooster flush during runtime suspend.
> 
> However the UFS specification mentions,
> 
> "While the flushing operation is in progress, the device is
> in Active power mode."
> 
> Therefore UFS host driver needs to promise more: Keep UFS
> device as "Active power mode", otherwise UFS device shall not
> do any flush if device enters Sleep or PowerDown power mode.
> 
> Fix this by not changing device power mode if WriteBooster
> flush is required in ufshcd_suspend().
> 
> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
> ---
>   drivers/scsi/ufs/ufs.h    |  1 -
>   drivers/scsi/ufs/ufshcd.c | 39 +++++++++++++++++++--------------------
>   2 files changed, 19 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h
> index b3135344ab3f..9e4bc2e97ada 100644
> --- a/drivers/scsi/ufs/ufs.h
> +++ b/drivers/scsi/ufs/ufs.h
> @@ -577,7 +577,6 @@ struct ufs_dev_info {
>   	u32 d_ext_ufs_feature_sup;
>   	u8 b_wb_buffer_type;
>   	u32 d_wb_alloc_units;
> -	bool keep_vcc_on;
>   	u8 b_presrv_uspc_en;
>   };
>   
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 169a3379e468..2d0aff8ac260 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -8101,8 +8101,7 @@ static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)
>   	    !hba->dev_info.is_lu_power_on_wp) {
>   		ufshcd_setup_vreg(hba, false);
>   	} else if (!ufshcd_is_ufs_dev_active(hba)) {
> -		if (!hba->dev_info.keep_vcc_on)
> -			ufshcd_toggle_vreg(hba->dev, hba->vreg_info.vcc, false);
> +		ufshcd_toggle_vreg(hba->dev, hba->vreg_info.vcc, false);
>   		if (!ufshcd_is_link_active(hba)) {
>   			ufshcd_config_vreg_lpm(hba, hba->vreg_info.vccq);
>   			ufshcd_config_vreg_lpm(hba, hba->vreg_info.vccq2);
> @@ -8172,6 +8171,7 @@ 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)) {
> @@ -8226,28 +8226,27 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>   			/* make sure that auto bkops is disabled */
>   			ufshcd_disable_auto_bkops(hba);
>   		}
> +
Unnecessary newline, perhaps?
>   		/*
> -		 * With wb enabled, if the bkops is enabled or if the
> -		 * configured WB type is 70% full, keep vcc ON
> -		 * for the device to flush the wb buffer
> +		 * If device needs to do BKOP or WB buffer flush, keep device
> +		 * power mode as "active power mode" and its VCC supply.
>   		 */
> -		if ((hba->auto_bkops_enabled && ufshcd_is_wb_allowed(hba)) ||
> -		    ufshcd_wb_keep_vcc_on(hba))
> -			hba->dev_info.keep_vcc_on = true;
> -		else
> -			hba->dev_info.keep_vcc_on = false;
> -	} else {
> -		hba->dev_info.keep_vcc_on = false;
> +		keep_curr_dev_pwr_mode = hba->auto_bkops_enabled ||
> +			ufshcd_wb_keep_vcc_on(hba);
Should the device be in UFS_ACTIVE_PWR_MODE to perform auto-bkops?

Also, is it needed to keep the device in UFS_ACTIVE_PWR_MODE , if flush 
on hibern8 is enabled and the link is being put to hibern8 mode during 
runtime-suspend? Perhaps that should also be factored in here?
>   	}
>   
> -	if ((req_dev_pwr_mode != hba->curr_dev_pwr_mode) &&
> -	    ((ufshcd_is_runtime_pm(pm_op) && !hba->auto_bkops_enabled) ||
> -	    !ufshcd_is_runtime_pm(pm_op))) {
> -		/* ensure that bkops is disabled */
> -		ufshcd_disable_auto_bkops(hba);
> -		ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);
> -		if (ret)
> -			goto enable_gating;
> +	if (req_dev_pwr_mode != hba->curr_dev_pwr_mode) {
> +		if ((ufshcd_is_runtime_pm(pm_op) && !hba->auto_bkops_enabled) ||
> +		    !ufshcd_is_runtime_pm(pm_op)) {
> +			/* ensure that bkops is disabled */
> +			ufshcd_disable_auto_bkops(hba);
> +		}
> +
> +		if (!keep_curr_dev_pwr_mode) {
> +			ret = ufshcd_set_dev_pwr_mode(hba, req_dev_pwr_mode);

Now, when the WB buffer is completely flushed out, the device should be 
put back into UFS_SLEEP_PWR_MODE or UFS_POWERDOWN_PWR_MODE. Say, the 
device buffer has to be flushed and during runtime-suspend, the device 
is put to UFS_ACTIVE_PWR_MODE and Vcc is kept ON; the device doesn't 
resume nor does the system enters suspend for a very long time, and with 
AH8 and hibern8 disabled, there will be an unnecessary power drain for 
that much time.

How about a periodic interval checking of flush status if 
keep_curr_dev_pwr_mode evaluates to be true?

> +			if (ret)
> +				goto enable_gating;
> +		}
>   	}
>   
>   	flush_work(&hba->eeh_work);
> 



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