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

[Kyuho Choi <chlrbgh0@gmail.com>]

Hi Sayali,

On 6/1/18, Sayali Lokhande <sayalil@codeaurora.org> wrote:
> From: Subhash Jadavani <subhashj@codeaurora.org>
>
> 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@codeaurora.org>
> [cang@codeaurora.org: Resolved trivial merge conflicts]
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
> ---
>  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)) {
> +		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]);
> +
> +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);

How it works in 26MHz refclk support host like exynos series?. As I
understood, there default refclk value are 26MHz for host and device.
In that case, your code maybe set device's refclk to 19.2MHz. It would
be need to set same refclk value both host and device for switch to
HS.

>  		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
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
>

BR,
Kyuho Choi