Re: [PATCH] usb: phy: mxs: Add DT bindings to configure TX settings

[Peter Chen <hzpeterchen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Tue, Aug 16, 2016 at 06:31:48PM -0400, Jaret Cantu wrote:
> The TX settings can be calibrated for particular hardware.  The
> phy is reset by Linux, so this cannot be handled by the bootloader.
> 
> The TRM mentions that the maximum resistance should be used for the
> DN/DP calibration in order to pass USB certification.
> 
> The values for the TX registers are poorly described in the TRM.
> The meanings of the register values were taken from another
> NXP-provided document:
> https://community.nxp.com/message/566147#comment-566912
> 
> Signed-off-by: Jaret Cantu <jaret.cantu-jEh4hwF5bVhBDgjK7y7TUQ@public.gmane.org>
> ---
> v4. Corrected tx-d-cal register value by rounding up.
>     Changed Freescale web site reference to NXP.
> 
> v3. Added unit suffix (-ohms) to tx-cal-45-d*
> 
> v2. Copying devicetree list
>     Removed prettifying extra whitespace
>     Removed unnecessary register rewrite on resume
>     Use min and max constants for clarity
> 
>  .../devicetree/bindings/phy/mxs-usb-phy.txt        |   10 ++++
>  drivers/usb/phy/phy-mxs-usb.c                      |   61 ++++++++++++++++++++
>  2 files changed, 71 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt b/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt
> index 379b84a..1d25b04 100644
> --- a/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt
> +++ b/Documentation/devicetree/bindings/phy/mxs-usb-phy.txt
> @@ -12,6 +12,16 @@ Required properties:
>  - interrupts: Should contain phy interrupt
>  - fsl,anatop: phandle for anatop register, it is only for imx6 SoC series
>  
> +Optional properties:
> +- fsl,tx-cal-45-dn-ohms: Integer [30-55]. Resistance (in ohms) of switchable
> +  high-speed trimming resistor connected in parallel with the 45 ohm resistor
> +  that terminates the DN output signal. Default: 45
> +- fsl,tx-cal-45-dp-ohms: Integer [30-55]. Resistance (in ohms) of switchable
> +  high-speed trimming resistor connected in parallel with the 45 ohm resistor
> +  that terminates the DP output signal. Default: 45
> +- fsl,tx-d-cal: Integer [79-119]. Current trimming value (as a percentage) of
> +  the 17.78mA TX reference current. Default: 100
> +
>  Example:
>  usbphy1: usbphy@020c9000 {
>  	compatible = "fsl,imx6q-usbphy", "fsl,imx23-usbphy";
> diff --git a/drivers/usb/phy/phy-mxs-usb.c b/drivers/usb/phy/phy-mxs-usb.c
> index 00bfea0..0e2f1a3 100644
> --- a/drivers/usb/phy/phy-mxs-usb.c
> +++ b/drivers/usb/phy/phy-mxs-usb.c
> @@ -27,6 +27,7 @@
>  #define DRIVER_NAME "mxs_phy"
>  
>  #define HW_USBPHY_PWD				0x00
> +#define HW_USBPHY_TX				0x10
>  #define HW_USBPHY_CTRL				0x30
>  #define HW_USBPHY_CTRL_SET			0x34
>  #define HW_USBPHY_CTRL_CLR			0x38
> @@ -38,6 +39,10 @@
>  #define HW_USBPHY_IP_SET			0x94
>  #define HW_USBPHY_IP_CLR			0x98
>  
> +#define GM_USBPHY_TX_TXCAL45DP(x)            (((x) & 0xf) << 16)
> +#define GM_USBPHY_TX_TXCAL45DN(x)            (((x) & 0xf) << 8)
> +#define GM_USBPHY_TX_D_CAL(x)                (((x) & 0xf) << 0)
> +
>  #define BM_USBPHY_CTRL_SFTRST			BIT(31)
>  #define BM_USBPHY_CTRL_CLKGATE			BIT(30)
>  #define BM_USBPHY_CTRL_OTG_ID_VALUE		BIT(27)
> @@ -115,6 +120,12 @@
>   */
>  #define MXS_PHY_NEED_IP_FIX			BIT(3)
>  
> +/* Minimum and maximum values for device tree entries */
> +#define MXS_PHY_TX_CAL45_MIN			30
> +#define MXS_PHY_TX_CAL45_MAX			55
> +#define MXS_PHY_TX_D_CAL_MIN			79
> +#define MXS_PHY_TX_D_CAL_MAX			119
> +
>  struct mxs_phy_data {
>  	unsigned int flags;
>  };
> @@ -164,6 +175,8 @@ struct mxs_phy {
>  	const struct mxs_phy_data *data;
>  	struct regmap *regmap_anatop;
>  	int port_id;
> +	u32 tx_reg_set;
> +	u32 tx_reg_mask;
>  };
>  
>  static inline bool is_imx6q_phy(struct mxs_phy *mxs_phy)
> @@ -185,6 +198,20 @@ static void mxs_phy_clock_switch_delay(void)
>  	usleep_range(300, 400);
>  }
>  
> +static void mxs_phy_tx_init(struct mxs_phy *mxs_phy)
> +{
> +	void __iomem *base = mxs_phy->phy.io_priv;
> +	u32 phytx;
> +
> +	/* Update TX register if there is anything to write */
> +	if (mxs_phy->tx_reg_mask) {
> +		phytx = readl(base + HW_USBPHY_TX);
> +		phytx &= ~mxs_phy->tx_reg_mask;
> +		phytx |= mxs_phy->tx_reg_set;
> +		writel(phytx, base + HW_USBPHY_TX);
> +	}
> +}
> +
>  static int mxs_phy_hw_init(struct mxs_phy *mxs_phy)
>  {
>  	int ret;
> @@ -214,6 +241,8 @@ static int mxs_phy_hw_init(struct mxs_phy *mxs_phy)
>  	if (mxs_phy->data->flags & MXS_PHY_NEED_IP_FIX)
>  		writel(BM_USBPHY_IP_FIX, base + HW_USBPHY_IP_SET);
>  
> +	mxs_phy_tx_init(mxs_phy);
> +
>  	return 0;
>  }
>  
> @@ -459,6 +488,7 @@ static int mxs_phy_probe(struct platform_device *pdev)
>  	int ret;
>  	const struct of_device_id *of_id;
>  	struct device_node *np = pdev->dev.of_node;
> +	u32 val;
>  
>  	of_id = of_match_device(mxs_phy_dt_ids, &pdev->dev);
>  	if (!of_id)
> @@ -491,6 +521,37 @@ static int mxs_phy_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	/* Precompute which bits of the TX register are to be updated, if any */
> +	if (!of_property_read_u32(np, "fsl,tx-cal-45-dn-ohms", &val) &&
> +	    val >= MXS_PHY_TX_CAL45_MIN && val <= MXS_PHY_TX_CAL45_MAX) {
> +		/* Scale to a 4-bit value */
> +		val = (MXS_PHY_TX_CAL45_MAX - val) * 0xF
> +			/ (MXS_PHY_TX_CAL45_MAX - MXS_PHY_TX_CAL45_MIN);
> +		mxs_phy->tx_reg_mask |= GM_USBPHY_TX_TXCAL45DN(~0);
> +		mxs_phy->tx_reg_set  |= GM_USBPHY_TX_TXCAL45DN(val);
> +	}
> +
> +	if (!of_property_read_u32(np, "fsl,tx-cal-45-dp-ohms", &val) &&
> +	    val >= MXS_PHY_TX_CAL45_MIN && val <= MXS_PHY_TX_CAL45_MAX) {
> +		/* Scale to a 4-bit value. */
> +		val = (MXS_PHY_TX_CAL45_MAX - val) * 0xF
> +			/ (MXS_PHY_TX_CAL45_MAX - MXS_PHY_TX_CAL45_MIN);
> +		mxs_phy->tx_reg_mask |= GM_USBPHY_TX_TXCAL45DP(~0);
> +		mxs_phy->tx_reg_set  |= GM_USBPHY_TX_TXCAL45DP(val);
> +	}
> +
> +	if (!of_property_read_u32(np, "fsl,tx-d-cal", &val) &&
> +	    val >= MXS_PHY_TX_D_CAL_MIN && val <= MXS_PHY_TX_D_CAL_MAX) {
> +		/* Scale to a 4-bit value.  Round up the values and heavily
> +		 * weight the rounding by adding 2/3 of the denominator.
> +		 */
> +		val = ((MXS_PHY_TX_D_CAL_MAX - val) * 0xF
> +			+ (MXS_PHY_TX_D_CAL_MAX - MXS_PHY_TX_D_CAL_MIN) * 2/3)
> +			/ (MXS_PHY_TX_D_CAL_MAX - MXS_PHY_TX_D_CAL_MIN);
> +		mxs_phy->tx_reg_mask |= GM_USBPHY_TX_D_CAL(~0);
> +		mxs_phy->tx_reg_set  |= GM_USBPHY_TX_D_CAL(val);
> +	}
> +
>  	ret = of_alias_get_id(np, "usbphy");
>  	if (ret < 0)
>  		dev_dbg(&pdev->dev, "failed to get alias id, errno %d\n", ret);
> -- 

Acked-by: Peter Chen <peter.chen-3arQi8VN3Tc@public.gmane.org>

-- 

Best Regards,
Peter Chen
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