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

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Date:   Wed, 05 Feb 2020 12:52:10 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Stanley Chu <stanley.chu@...iatek.com>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Bean Huo <beanhuo@...ron.com>,
        Colin Ian King <colin.king@...onical.com>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Bart Van Assche <bvanassche@....org>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 6/8] scsi: ufs: Add dev ref clock gating wait time
 support

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@...eaurora.org>
>> Reviewed-by: Asutosh Das <asutoshd@...eaurora.org>
>> ---
>>  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,