Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB on/off

[Can Guo]

On 2020-12-22 14:08, Stanley Chu wrote:
> Hi Bean,
>
> On Wed, 2020-12-16 at 00:05 +0100, Bean Huo wrote:
> > From: Bean Huo <beanhuo@xxxxxxxxxx>
> >
> > Currently UFS WriteBooster driver uses clock scaling up/down to set
> > WB on/off, for the platform which doesn't support 
> > UFSHCD_CAP_CLK_SCALING,
> > WB will be always on. Provide a sysfs attribute to enable/disable WB
> > during runtime. Write 1/0 to "wb_on" sysfs node to enable/disable UFS 
> > WB.
> >
> > Reviewed-by: Avri Altman <avri.altman@xxxxxxx>
> > Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> > Signed-off-by: Bean Huo <beanhuo@xxxxxxxxxx>
> > ---
> >  drivers/scsi/ufs/ufs-sysfs.c | 41 
> > ++++++++++++++++++++++++++++++++++++
> >  drivers/scsi/ufs/ufshcd.c    |  3 +--
> >  drivers/scsi/ufs/ufshcd.h    |  2 ++
> >  3 files changed, 44 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufs-sysfs.c 
> > b/drivers/scsi/ufs/ufs-sysfs.c
> > index 08e72b7eef6a..f3ca3d6b82c4 100644
> > --- a/drivers/scsi/ufs/ufs-sysfs.c
> > +++ b/drivers/scsi/ufs/ufs-sysfs.c
> > @@ -189,6 +189,45 @@ static ssize_t auto_hibern8_store(struct device 
> > *dev,
> >  	return count;
> >  }
> >
> > +static ssize_t wb_on_show(struct device *dev, struct device_attribute 
> > *attr,
> > +			  char *buf)
> > +{
> > +	struct ufs_hba *hba = dev_get_drvdata(dev);
> > +
> > +	return sysfs_emit(buf, "%d\n", hba->wb_enabled);
> > +}
> > +
> > +static ssize_t wb_on_store(struct device *dev, struct 
> > device_attribute *attr,
> > +			   const char *buf, size_t count)
> > +{
> > +	struct ufs_hba *hba = dev_get_drvdata(dev);
> > +	unsigned int wb_enable;
> > +	ssize_t res;
> > +
> > +	if (ufshcd_is_clkscaling_supported(hba)) {
> > +		/*
> > +		 * If the platform supports UFSHCD_CAP_CLK_SCALING, turn WB
> > +		 * on/off will be done while clock scaling up/down.
> > +		 */
> > +		dev_warn(dev, "To control WB through wb_on is not allowed!\n");
> > +		return -EOPNOTSUPP;
> > +	}
> > +	if (!ufshcd_is_wb_allowed(hba))
> > +		return -EOPNOTSUPP;
> > +
> > +	if (kstrtouint(buf, 0, &wb_enable))
> > +		return -EINVAL;
> > +
> > +	if (wb_enable != 0 && wb_enable != 1)
> > +		return -EINVAL;
> > +
> > +	pm_runtime_get_sync(hba->dev);
> > +	res = ufshcd_wb_ctrl(hba, wb_enable);
>
> May this operation race with UFS shutdown flow?
>
> To be more clear, ufshcd_wb_ctrl() here may be executed after host 
> clock
> is disabled by shutdown flow?
>
> If yes, we need to avoid it.

I have the same doubt - can user still access sysfs nodes after system
starts to run shutdown routines? If yes, then we need to remove all UFS
sysfs nodes in ufshcd_shutdown().

Thanks,

Can Guo.

> Thanks,
> Stanley Chu
>
> > +	pm_runtime_put_sync(hba->dev);
> > +
> > +	return res < 0 ? res : count;
> > +}
> > +
> >  static DEVICE_ATTR_RW(rpm_lvl);
> >  static DEVICE_ATTR_RO(rpm_target_dev_state);
> >  static DEVICE_ATTR_RO(rpm_target_link_state);
> > @@ -196,6 +235,7 @@ static DEVICE_ATTR_RW(spm_lvl);
> >  static DEVICE_ATTR_RO(spm_target_dev_state);
> >  static DEVICE_ATTR_RO(spm_target_link_state);
> >  static DEVICE_ATTR_RW(auto_hibern8);
> > +static DEVICE_ATTR_RW(wb_on);
> >
> >  static struct attribute *ufs_sysfs_ufshcd_attrs[] = {
> >  	&dev_attr_rpm_lvl.attr,
> > @@ -205,6 +245,7 @@ static struct attribute *ufs_sysfs_ufshcd_attrs[] 
> > = {
> >  	&dev_attr_spm_target_dev_state.attr,
> >  	&dev_attr_spm_target_link_state.attr,
> >  	&dev_attr_auto_hibern8.attr,
> > +	&dev_attr_wb_on.attr,
> >  	NULL
> >  };
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index e221add25a7e..5e1dcf4de67e 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -246,7 +246,6 @@ static inline int ufshcd_config_vreg_hpm(struct 
> > ufs_hba *hba,
> >  static int ufshcd_try_to_abort_task(struct ufs_hba *hba, int tag);
> >  static int ufshcd_wb_buf_flush_enable(struct ufs_hba *hba);
> >  static int ufshcd_wb_buf_flush_disable(struct ufs_hba *hba);
> > -static int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable);
> >  static int ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool 
> > set);
> >  static inline void ufshcd_wb_toggle_flush(struct ufs_hba *hba, bool 
> > enable);
> >  static void ufshcd_hba_vreg_set_lpm(struct ufs_hba *hba);
> > @@ -5351,7 +5350,7 @@ static void 
> > ufshcd_bkops_exception_event_handler(struct ufs_hba *hba)
> >  				__func__, err);
> >  }
> >
> > -static int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable)
> > +int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable)
> >  {
> >  	int ret;
> >  	u8 index;
> > diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> > index 9bb5f0ed4124..2a97006a2c93 100644
> > --- a/drivers/scsi/ufs/ufshcd.h
> > +++ b/drivers/scsi/ufs/ufshcd.h
> > @@ -1068,6 +1068,8 @@ int ufshcd_exec_raw_upiu_cmd(struct ufs_hba 
> > *hba,
> >  			     u8 *desc_buff, int *buff_len,
> >  			     enum query_opcode desc_op);
> >
> > +int ufshcd_wb_ctrl(struct ufs_hba *hba, bool enable);
> > +
> >  /* Wrapper functions for safely calling variant operations */
> >  static inline const char *ufshcd_get_var_name(struct ufs_hba *hba)
> >  {