Message-ID: <50D0F9EA.9090002@gmail.com>
Date:	Wed, 19 Dec 2012 00:19:06 +0100
From:	Sylwester Nawrocki <sylvester.nawrocki@...il.com>
To:	Vivek Gautam <gautam.vivek@...sung.com>
CC:	linux-usb@...r.kernel.org, l.majewski@...sung.com,
	linux-samsung-soc@...r.kernel.org, p.paneri@...sung.com,
	gregkh@...uxfoundation.org, devicetree-discuss@...ts.ozlabs.org,
	broonie@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org,
	balbi@...com, kyungmin.park@...sung.com, kgene.kim@...sung.com,
	ben-linux@...ff.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] usb: phy: samsung: Add support to set pmu isolation

Hi Vivek,

On 12/18/2012 02:56 PM, Vivek Gautam wrote:
> Adding support to parse device node data in order to get
> required properties to set pmu isolation for usb-phy.
>
> Signed-off-by: Vivek Gautam<gautam.vivek@...sung.com>
> ---
>
> Changes from v1:
>   - Changed the name of property for phy handler from'samsung,usb-phyctrl'
>     to 'samsung,usb-phyhandle' to make it look more generic.
>   - Similarly 'samsung,phyctrl-reg' is changed to 'samsung,phyhandle-reg'
>   - Added a check for 'samsung,usb-phyhandle' before getting node from
>     phandle.
>   - Putting the node using 'of_node_put()' which had been missed.
>   - Adding necessary check for the pointer in 'samsung_usbphy_set_isolation()'
>     to avoid any NULL pointer dereferencing.
>   - Unmapping the register ioremapped in 'samsung_usbphy_parse_dt_param()'.
>
>
>   .../devicetree/bindings/usb/samsung-usbphy.txt     |   12 +++
>   drivers/usb/phy/samsung-usbphy.c                   |   94 ++++++++++++++++++--
>   2 files changed, 98 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/usb/samsung-usbphy.txt b/Documentation/devicetree/bindings/usb/samsung-usbphy.txt
> index 7b26e2d..a7b28b2 100644
> --- a/Documentation/devicetree/bindings/usb/samsung-usbphy.txt
> +++ b/Documentation/devicetree/bindings/usb/samsung-usbphy.txt
> @@ -9,3 +9,15 @@ Required properties:
>   - compatible : should be "samsung,exynos4210-usbphy"
>   - reg : base physical address of the phy registers and length of memory mapped
>   	region.
> +
> +Optional properties:
> +- samsung,usb-phyhandle : should point to usb-phyhandle sub-node which provides
> +			binding data to enable/disable device PHY handled by
> +			PMU register.
> +
> +			Required properties:
> +			- compatible : should be "samsung,usbdev-phyctrl" for
> +					DEVICE type phy.
> +			- samsung,phyhandle-reg: base physical address of
> +						PHY_CONTROL register in PMU.
> +- samsung,enable-mask : should be '1'

This should only be 1 for Exynos4210+ SoCs, right ?
S5PV210 uses bit 0 for OTG and bit1 for USB host, doesn't it ? And for 
s3c64xx
it seems to be bit 16.

How about deriving this information from 'compatible' property instead ?

Maybe you could just encode the USB PMU registers (I assume those aren't
touched by anything but the usb drivers) in a regular 'reg' property in
an usbphy subnode. Then the driver could interpret it also with help
of 'compatible' property. And you could just use of_iomap(). E.g.

  usbphy@...30000 {
  	compatible = "samsung,exynos5250-usbphy";
	reg = <0x12130000 0x100>, <0x12100000 0x100>;
	usbphy-pmu {
		/* USB device and host PHY_CONTROL registers */
		reg = <0x10040704 8>;
	};
  };

Your "samsung,usb-phyhandle" approach seems over-engineered to me.
I might be missing something though.

> diff --git a/drivers/usb/phy/samsung-usbphy.c b/drivers/usb/phy/samsung-usbphy.c
> index 5c5e1bb5..4ceabe3 100644
> --- a/drivers/usb/phy/samsung-usbphy.c
> +++ b/drivers/usb/phy/samsung-usbphy.c
> @@ -72,6 +72,8 @@ enum samsung_cpu_type {
>    * @dev: The parent device supplied to the probe function
>    * @clk: usb phy clock
>    * @regs: usb phy register memory base
> + * @devctrl_reg: usb device phy-control pmu register memory base

hum, this name is not really helpful in understanding what's going
on here.

Looking at arch/arm/mach-s5pv210/setup-usb-phy.c, there is only one
PHY_CONTROL (Power Management Unit) register for both OTG and USB host
PHYs. So are you really taking care of that case as well ?

> + * @en_mask: enable mask
>    * @ref_clk_freq: reference clock frequency selection
>    * @cpu_type: machine identifier
>    */
> @@ -81,12 +83,73 @@ struct samsung_usbphy {
>   	struct device	*dev;
>   	struct clk	*clk;
>   	void __iomem	*regs;
> +	void __iomem	*devctrl_reg;
> +	u32		en_mask;
>   	int		ref_clk_freq;
>   	int		cpu_type;
>   };
>
>   #define phy_to_sphy(x)		container_of((x), struct samsung_usbphy, phy)
>
> +static int samsung_usbphy_parse_dt_param(struct samsung_usbphy *sphy)
> +{
> +	struct device_node *usb_phyctrl;
> +	u32 reg;
> +	int lenp;
> +
> +	if (!sphy->dev->of_node) {
> +		sphy->devctrl_reg = NULL;
> +		return -ENODEV;
> +	}
> +
> +	if (of_get_property(sphy->dev->of_node, "samsung,usb-phyhandle",&lenp)) {
> +		usb_phyctrl = of_parse_phandle(sphy->dev->of_node,
> +						"samsung,usb-phyhandle", 0);
> +		if (!usb_phyctrl) {
> +			dev_warn(sphy->dev, "Can't get usb-phy handle\n");
> +			sphy->devctrl_reg = NULL;
> +		}
> +
> +		of_property_read_u32(usb_phyctrl, "samsung,phyhandle-reg",&reg);
> +
> +		sphy->devctrl_reg = ioremap(reg, SZ_4);

What happens if invalid address value is assigned to 
'samsung,phyhandle-reg' ?

> +		of_property_read_u32(sphy->dev->of_node, "samsung,enable-mask",
> +							&sphy->en_mask);
> +		of_node_put(usb_phyctrl);
> +	} else {
> +		dev_warn(sphy->dev, "Can't get usb-phy handle\n");
> +		sphy->devctrl_reg = NULL;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Set isolation here for phy.
> + * SOCs control this by controlling corresponding PMU registers
> + */
> +static void samsung_usbphy_set_isolation(struct samsung_usbphy *sphy, int on)
> +{
> +	void __iomem *usb_phyctrl_reg;
> +	u32 en_mask = sphy->en_mask;
> +	u32 reg;
> +
> +	usb_phyctrl_reg = sphy->devctrl_reg;
> +
> +	if (!usb_phyctrl_reg) {
> +		dev_warn(sphy->dev, "Can't set pmu isolation\n");
> +		return;
> +	}
> +
> +	reg = readl(usb_phyctrl_reg);
> +
> +	if (on)
> +		writel(reg&  ~en_mask, usb_phyctrl_reg);
> +	else
> +		writel(reg | en_mask, usb_phyctrl_reg);
> +}
> +
>   /*
>    * Returns reference clock frequency selection value
>    */
> @@ -199,6 +262,8 @@ static int samsung_usbphy_init(struct usb_phy *phy)
>   	/* Disable phy isolation */
>   	if (sphy->plat&&  sphy->plat->pmu_isolation)
>   		sphy->plat->pmu_isolation(false);
> +	else
> +		samsung_usbphy_set_isolation(sphy, false);
>
>   	/* Initialize usb phy registers */
>   	samsung_usbphy_enable(sphy);
> @@ -228,6 +293,8 @@ static void samsung_usbphy_shutdown(struct usb_phy *phy)
>   	/* Enable phy isolation */
>   	if (sphy->plat&&  sphy->plat->pmu_isolation)
>   		sphy->plat->pmu_isolation(true);
> +	else
> +		samsung_usbphy_set_isolation(sphy, true);
>
>   	clk_disable_unprepare(sphy->clk);
>   }
> @@ -249,17 +316,12 @@ static inline int samsung_usbphy_get_driver_data(struct platform_device *pdev)
>   static int __devinit samsung_usbphy_probe(struct platform_device *pdev)
>   {
>   	struct samsung_usbphy *sphy;
> -	struct samsung_usbphy_data *pdata;
> +	struct samsung_usbphy_data *pdata = pdev->dev.platform_data;
>   	struct device *dev =&pdev->dev;
>   	struct resource *phy_mem;
>   	void __iomem	*phy_base;
>   	struct clk *clk;
> -
> -	pdata = pdev->dev.platform_data;
> -	if (!pdata) {
> -		dev_err(&pdev->dev, "%s: no platform data defined\n", __func__);
> -		return -EINVAL;
> -	}
> +	int ret;
>
>   	phy_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>   	if (!phy_mem) {
> @@ -283,7 +345,20 @@ static int __devinit samsung_usbphy_probe(struct platform_device *pdev)
>   		return PTR_ERR(clk);
>   	}
>
> -	sphy->dev		=&pdev->dev;
> +	sphy->dev =&pdev->dev;

	sphy->dev = dev;

> +
> +	ret = samsung_usbphy_parse_dt_param(sphy);
> +	if (ret) {
> +		/* fallback to pdata */
> +		if (!pdata) {
> +			dev_err(&pdev->dev,
> +				"%s: no device data found\n", __func__);

I find term "device data" a bit confusing here.

> +			return -ENODEV;

In the original code -EINVAL was returned when platform_data was not set.

> +		} else {
> +			sphy->plat = pdata;
> +		}
> +	}
> +

How about rewriting this to:

	if (dev->of_node) {
		ret = samsung_usbphy_parse_dt_param(sphy);
		if (ret < 0)
			return ret;
	} else {
		if (!pdata) {
			dev_err(dev, "no platform data specified\n");
			return -EINVAL;
		}
	}	

This way we won't be obfuscating any error code returned from the
OF parsing function.

>   	sphy->plat		= pdata;
>   	sphy->regs		= phy_base;
>   	sphy->clk		= clk;
> @@ -305,6 +380,9 @@ static int __exit samsung_usbphy_remove(struct platform_device *pdev)
>
>   	usb_remove_phy(&sphy->phy);
>
> +	if (sphy->devctrl_reg)
> +		iounmap(sphy->devctrl_reg);
> +
>   	return 0;
>   }

--

Regards,
Sylwester
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