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

Stanley Chu
2020-12-22T06:09:39Z

Hi Bean,

On Wed, 2020-12-16 at 00:05 +0100, Bean Huo wrote:
> From: Bean Huo <beanhuo@micron.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@wdc.com>
> Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
> Signed-off-by: Bean Huo <beanhuo@micron.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.

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)
> {