Re: [PATCH v5 6/8] scsi: ufs: Add dev ref clock gating wait time support

[Can Guo <cang@xxxxxxxxxxxxxx>]

On 2020-02-05 10:50, Stanley Chu wrote:
> Hi Can,
>
> On Mon, 2020-02-03 at 01:17 -0800, Can Guo wrote:
> > In UFS version 3.0, a newly added attribute bRefClkGatingWaitTime 
> > defines
> > the minimum time for which the reference clock is required by device 
> > during
> > transition to LS-MODE or HIBERN8 state. Make this change to reflect 
> > the new
> > requirement by adding delays before turning off the clock.
> >
> > Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> > Reviewed-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> > ---
> >  drivers/scsi/ufs/ufs.h    |  3 +++
> >  drivers/scsi/ufs/ufshcd.c | 40 
> > ++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 43 insertions(+)
> >
> > diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h
> > index cfe3803..304076e 100644
> > --- a/drivers/scsi/ufs/ufs.h
> > +++ b/drivers/scsi/ufs/ufs.h
> > @@ -167,6 +167,7 @@ enum attr_idn {
> >  	QUERY_ATTR_IDN_FFU_STATUS		= 0x14,
> >  	QUERY_ATTR_IDN_PSA_STATE		= 0x15,
> >  	QUERY_ATTR_IDN_PSA_DATA_SIZE		= 0x16,
> > +	QUERY_ATTR_IDN_REF_CLK_GATING_WAIT_TIME	= 0x17,
> >  };
> >
> >  /* Descriptor idn for Query requests */
> > @@ -534,6 +535,8 @@ struct ufs_dev_info {
> >  	u16 wmanufacturerid;
> >  	/*UFS device Product Name */
> >  	u8 *model;
> > +	u16 spec_version;
> > +	u32 clk_gating_wait_us;
> >  };
> >
> >  /**
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index e8f7f9d..d5c547b 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -91,6 +91,9 @@
> >  /* default delay of autosuspend: 2000 ms */
> >  #define RPM_AUTOSUSPEND_DELAY_MS 2000
> >
> > +/* Default value of wait time before gating device ref clock */
> > +#define UFSHCD_REF_CLK_GATING_WAIT_US 0xFF /* microsecs */
> > +
> >  #define ufshcd_toggle_vreg(_dev, _vreg, _on)				\
> >  	({                                                              \
> >  		int _ret;                                               \
> > @@ -3281,6 +3284,37 @@ static inline int 
> > ufshcd_read_unit_desc_param(struct ufs_hba *hba,
> >  				      param_offset, param_read_buf, param_size);
> >  }
> >
> > +static int ufshcd_get_ref_clk_gating_wait(struct ufs_hba *hba)
> > +{
> > +	int err = 0;
> > +	u32 gating_wait = UFSHCD_REF_CLK_GATING_WAIT_US;
> > +
> > +	if (hba->dev_info.spec_version >= 0x300) {
> > +		err = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_READ_ATTR,
> > +				QUERY_ATTR_IDN_REF_CLK_GATING_WAIT_TIME, 0, 0,
> > +				&gating_wait);
> > +		if (err)
> > +			dev_err(hba->dev, "Failed reading bRefClkGatingWait. err = %d, use 
> > default %uus\n",
> > +					 err, gating_wait);
> > +
> > +		if (gating_wait == 0) {
> > +			gating_wait = UFSHCD_REF_CLK_GATING_WAIT_US;
> > +			dev_err(hba->dev, "Undefined ref clk gating wait time, use default 
> > %uus\n",
> > +					 gating_wait);
> > +		}
> > +
> > +		/*
> > +		 * bRefClkGatingWaitTime defines the minimum time for which the
> > +		 * reference clock is required by device during transition from
> > +		 * HS-MODE to LS-MODE or HIBERN8 state. Give it more time to be
> > +		 * on the safe side.
> > +		 */
> > +		hba->dev_info.clk_gating_wait_us = gating_wait + 50;
>
>
> Not sure if the additional 50us wait time here is too large.
>
> Is there any special reason to fix it as "50"?
>
>
> Thanks,
> Stanley

Hi Stanley,

We used to ask vendors about it, 50 is somehow agreed by them. Do you 
have a
better value in mind?

For me, I just wanted to give it 10, so that we can directly use 
usleep_range
with it, no need to decide whether to use udelay or usleep_range.

Thanks,
Can Guo.

> >  				      &dev_info->model, SD_ASCII_STD);
> > @@ -7003,6 +7041,8 @@ static int ufshcd_device_params_init(struct 
> > ufs_hba *hba)
> >  		goto out;
> >  	}
> >
> > +	ufshcd_get_ref_clk_gating_wait(hba);
> > +
> >  	ufs_fixup_device_setup(hba);
> >
> >  	if (!ufshcd_query_flag_retry(hba, UPIU_QUERY_OPCODE_READ_FLAG,