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Subject: Re: [PATCH V2 1/3] scsi: ufs: set the device reference clock setting
To:     Sayali Lokhande <sayalil@codeaurora.org>, subhashj@codeaurora.org,
        cang@codeaurora.org, vivek.gautam@codeaurora.org,
        rnayak@codeaurora.org, vinholikatti@gmail.com,
        jejb@linux.vnet.ibm.com, martin.petersen@oracle.com,
        asutoshd@codeaurora.org, evgreen@chromium.org
Cc:     linux-scsi@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Mathieu Malaterre <malat@debian.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
References: <1528455990-24572-1-git-send-email-sayalil@codeaurora.org>
 <1528455990-24572-2-git-send-email-sayalil@codeaurora.org>
From:   Adrian Hunter <adrian.hunter@intel.com>
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Date:   Fri, 8 Jun 2018 15:01:01 +0300
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On 08/06/18 14:06, Sayali Lokhande 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>
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
> ---
>  .../devicetree/bindings/ufs/ufshcd-pltfrm.txt      |  7 +++
>  drivers/scsi/ufs/ufs.h                             |  9 ++++
>  drivers/scsi/ufs/ufshcd-pltfrm.c                   | 24 ++++++++++
>  drivers/scsi/ufs/ufshcd.c                          | 52 ++++++++++++++++++++++
>  drivers/scsi/ufs/ufshcd.h                          |  1 +
>  5 files changed, 93 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> index c39dfef..4522434 100644
> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> @@ -41,6 +41,12 @@ Optional properties:
>  -lanes-per-direction	: number of lanes available per direction - either 1 or 2.
>  			  Note that it is assume same number of lanes is used both
>  			  directions at once. If not specified, default is 2 lanes per direction.
> +- dev-ref-clk-freq	: Specify the device reference clock frequency, must be one of the following:
> +			  0: 19.2 MHz
> +			  1: 26 MHz
> +			  2: 38.4 MHz
> +			  3: 52 MHz
> +			  Defaults to 26 MHz if not specified.
>  
>  Note: If above properties are not defined it can be assumed that the supply
>  regulators or clocks are always on.
> @@ -66,4 +72,5 @@ Example:
>  		freq-table-hz = <100000000 200000000>, <0 0>, <0 0>;
>  		phys = <&ufsphy1>;
>  		phy-names = "ufsphy";
> +		dev-ref-clk-freq = <0>; /* reference clock freq: 19.2 MHz */
>  	};
> 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-pltfrm.c b/drivers/scsi/ufs/ufshcd-pltfrm.c
> index e82bde0..6c877f3 100644
> --- a/drivers/scsi/ufs/ufshcd-pltfrm.c
> +++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
> @@ -221,6 +221,28 @@ static int ufshcd_parse_regulator_info(struct ufs_hba *hba)
>  	return err;
>  }
>  
> +static void ufshcd_parse_dev_ref_clk_freq(struct ufs_hba *hba)
> +{
> +	struct device *dev = hba->dev;
> +	struct device_node *np = dev->of_node;
> +	int ret;
> +
> +	if (!np)
> +		return;
> +
> +	ret = of_property_read_u32(np, "dev-ref-clk-freq",
> +				   &hba->dev_ref_clk_freq);

This setting is useful for any UFSHC driver.  Please move it to ufshcd.c and
use device_property_read_u32().

> +	if (ret ||
> +	    (hba->dev_ref_clk_freq < 0) ||

u32 cannot be < 0

> +	    (hba->dev_ref_clk_freq > REF_CLK_FREQ_52_MHZ)) {
> +		dev_err(hba->dev,
> +		"%s: invalid ref_clk setting = %d, set to default\n",
> +		__func__, hba->dev_ref_clk_freq);
> +		/* default setting */
> +		hba->dev_ref_clk_freq = REF_CLK_FREQ_26_MHZ;

No, the default is to leave the value unchanged.

> +	}
> +}
> +
>  #ifdef CONFIG_PM
>  /**
>   * ufshcd_pltfrm_suspend - suspend power management function
> @@ -343,6 +365,8 @@ int ufshcd_pltfrm_init(struct platform_device *pdev,
>  	pm_runtime_set_active(&pdev->dev);
>  	pm_runtime_enable(&pdev->dev);
>  
> +	ufshcd_parse_dev_ref_clk_freq(hba);
> +
>  	ufshcd_init_lanes_per_dir(hba);
>  
>  	err = ufshcd_init(hba, mmio_base, irq);
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index c5b1bf1..4abc7ae 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -6297,6 +6297,53 @@ static void ufshcd_def_desc_sizes(struct ufs_hba *hba)
>  }
>  
>  /**
> + * ufshcd_set_dev_ref_clk - set the device bRefClkFreq
> + * @hba: per-adapter instance
> + *
> + * 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)
> +{
> +	int err = 0;
> +	int ref_clk = -1;
> +	static const char * const ref_clk_freqs[] = {"19.2 MHz", "26 MHz",
> +						     "38.4 MHz", "52 MHz"};
> +
> +	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 == 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]);
> +	/*
> +	 * It is good to print this out here to debug any later failures
> +	 * related to gear switch.
> +	 */
> +	dev_dbg(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 +6408,11 @@ 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);
>  		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
>