RE: [PATCH V1 1/3] scsi: ufs: set the device reference clock setting

[sayali]

Hi Adrain,

Updated my comments inline. Please check.

Thanks,
Sayali
-----Original Message-----
From: Adrian Hunter [mailto:adrian.hunter@xxxxxxxxx] 
Sent: Friday, June 01, 2018 5:59 PM
To: Sayali Lokhande <sayalil@xxxxxxxxxxxxxx>; subhashj@xxxxxxxxxxxxxx; cang@xxxxxxxxxxxxxx; vivek.gautam@xxxxxxxxxxxxxx; rnayak@xxxxxxxxxxxxxx; vinholikatti@xxxxxxxxx; jejb@xxxxxxxxxxxxxxxxxx; martin.petersen@xxxxxxxxxx; asutoshd@xxxxxxxxxxxxxx; evgreen@xxxxxxxxxxxx
Cc: linux-scsi@xxxxxxxxxxxxxxx; open list <linux-kernel@xxxxxxxxxxxxxxx>
Subject: Re: [PATCH V1 1/3] scsi: ufs: set the device reference clock setting

On 01/06/18 13:42, Sayali Lokhande wrote:
> From: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
> 
> UFS host supplies the reference clock to UFS device and UFS device 
> specification allows host to provide one of the 4 frequencies (19.2 
> MHz,
> 26 MHz, 38.4 MHz, 52 MHz) for reference clock. Host should set the 
> device reference clock frequency setting in the device based on what 
> frequency it is supplying to UFS device.
> 
> Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
> [cang@xxxxxxxxxxxxxx: Resolved trivial merge conflicts]
> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> Signed-off-by: Sayali Lokhande <sayalil@xxxxxxxxxxxxxx>
> ---
>  drivers/scsi/ufs/ufs.h    |  9 +++++++
>  drivers/scsi/ufs/ufshcd.c | 62 
> +++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/scsi/ufs/ufshcd.h |  1 +
>  3 files changed, 72 insertions(+)
> 
> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h index 
> 14e5bf7..e15deb0 100644
> --- a/drivers/scsi/ufs/ufs.h
> +++ b/drivers/scsi/ufs/ufs.h
> @@ -378,6 +378,15 @@ enum query_opcode {
>  	UPIU_QUERY_OPCODE_TOGGLE_FLAG	= 0x8,
>  };
>  
> +/* bRefClkFreq attribute values */
> +enum ref_clk_freq {
> +	REF_CLK_FREQ_19_2_MHZ	= 0x0,
> +	REF_CLK_FREQ_26_MHZ	= 0x1,
> +	REF_CLK_FREQ_38_4_MHZ	= 0x2,
> +	REF_CLK_FREQ_52_MHZ	= 0x3,
> +	REF_CLK_FREQ_MAX	= REF_CLK_FREQ_52_MHZ,
> +};
> +
>  /* Query response result code */
>  enum {
>  	QUERY_RESULT_SUCCESS                    = 0x00,
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c 
> index c5b1bf1..3669bc4 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -6297,6 +6297,63 @@ static void ufshcd_def_desc_sizes(struct 
> ufs_hba *hba)  }
>  
>  /**
> + * ufshcd_set_dev_ref_clk - set the device bRefClkFreq
> + * @hba: per-adapter instance
> + * @ref_clk_freq: refrerence clock frequency to be set
> + *
> + * Read the current value of the bRefClkFreq attribute from device 
> +and update it
> + * if host is supplying different reference clock frequency than one 
> +mentioned
> + * in bRefClkFreq attribute.
> + *
> + * Returns zero on success, non-zero error value on failure.
> + */
> +static int ufshcd_set_dev_ref_clk(struct ufs_hba *hba, u32 
> +ref_clk_freq) {
> +	int err = 0;
> +	int ref_clk = -1;
> +	static const char * const ref_clk_freqs[] = {"19.2 MHz", "26 MHz",
> +						     "38.4 MHz", "52 MHz"};
> +
> +	hba->dev_ref_clk_freq = ref_clk_freq;
> +	err = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_READ_ATTR,
> +			QUERY_ATTR_IDN_REF_CLK_FREQ, 0, 0, &ref_clk);
> +
> +	if (err) {
> +		dev_err(hba->dev, "%s: failed reading bRefClkFreq. err = %d\n",
> +			 __func__, err);
> +		goto out;
> +	}
> +
> +	if ((ref_clk < 0) || (ref_clk > REF_CLK_FREQ_52_MHZ)) {

If you used u32 ref_clk then you wouldn't have to check < 0, also you should use REF_CLK_FREQ_MAX not REF_CLK_FREQ_52_MHZ, but really why is this check needed anyway?
[Sayali] Here ref_clk is defined as integer with value -1. We are then reading bRefClkFreq attribute from device into ref_clk and hence the sanity check is required before we update/write bRefClkFreq attribute.

> +		dev_err(hba->dev, "%s: invalid ref_clk setting = %d\n",
> +			 __func__, ref_clk);
> +		err = -EINVAL;
> +		goto out;
> +	}
> +
> +	if (ref_clk == hba->dev_ref_clk_freq)
> +		goto out; /* nothing to update */
> +
> +	err = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_WRITE_ATTR,
> +			QUERY_ATTR_IDN_REF_CLK_FREQ, 0, 0,
> +			&hba->dev_ref_clk_freq);
> +
> +	if (err)
> +		dev_err(hba->dev, "%s: bRefClkFreq setting to %s failed\n",
> +			__func__, ref_clk_freqs[hba->dev_ref_clk_freq]);
> +	else
> +		/*
> +		 * It is good to print this out here to debug any later failures
> +		 * related to gear switch.
> +		 */
> +		dev_info(hba->dev, "%s: bRefClkFreq setting to %s succeeded\n",
> +			__func__, ref_clk_freqs[hba->dev_ref_clk_freq]);

Why not make this dev_dbg and print always even when there is no update.
[Sayali] Agreed. Will update in next patchsets.

> +
> +out:
> +	return err;
> +}
> +
> +/**
>   * ufshcd_probe_hba - probe hba to detect device and initialize
>   * @hba: per-adapter instance
>   *
> @@ -6361,6 +6418,11 @@ static int ufshcd_probe_hba(struct ufs_hba *hba)
>  			"%s: Failed getting max supported power mode\n",
>  			__func__);
>  	} else {
> +		/*
> +		 * Set the right value to bRefClkFreq before attempting to
> +		 * switch to HS gears.
> +		 */
> +		ufshcd_set_dev_ref_clk(hba, REF_CLK_FREQ_19_2_MHZ);
>  		ret = ufshcd_config_pwr_mode(hba, &hba->max_pwr_info.info);
>  		if (ret) {
>  			dev_err(hba->dev, "%s: Failed setting power mode, err = %d\n", 
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h 
> index 8110dcd..b026ad8 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -548,6 +548,7 @@ struct ufs_hba {
>  	void *priv;
>  	unsigned int irq;
>  	bool is_irq_enabled;
> +	u32 dev_ref_clk_freq;
>  
>  	/* Interrupt aggregation support is broken */
>  	#define UFSHCD_QUIRK_BROKEN_INTR_AGGR			0x1
>