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

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Date:   Tue, 22 Dec 2020 14:12:49 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Stanley Chu <stanley.chu@...iatek.com>
Cc:     Bean Huo <huobean@...il.com>, alim.akhtar@...sung.com,
        avri.altman@....com, asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, beanhuo@...ron.com, bvanassche@....org,
        tomas.winkler@...el.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB
 on/off

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@...ron.com>
>> 
>> 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@....com>
>> Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>
>> Signed-off-by: Bean Huo <beanhuo@...ron.com>
>> ---
>>  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)
>>  {