linux-kernel - Re: [PATCH] phy: exynos5-usbdrd: Add facility to toggle vbus gpio on/off

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Message-ID: <CAFp+6iHKT6wFBimhzEGVJRiY_y-2rAur_e-TPFS9=RTLckf-rA@mail.gmail.com>
Date:	Thu, 10 Apr 2014 16:02:52 +0530
From:	Vivek Gautam <gautamvivek1987@...il.com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-doc@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>,
	Kamil Debski <k.debski@...sung.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Sylwester Nawrocki <sylvester.nawrocki@...il.com>
Subject: Re: [PATCH] phy: exynos5-usbdrd: Add facility to toggle vbus gpio on/off

Hi Kishon,


On Thu, Apr 10, 2014 at 2:39 PM, Kishon Vijay Abraham I <kishon@...com> wrote:
> Hi.
>
> On Wednesday 09 April 2014 05:24 PM, Vivek Gautam wrote:
>> Adding support to enable/disable VBUS hooked to a gpio
>> to enable vbus supply on the port.
>>
>> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
>> ---
>>
>> Based on 'phy-exynos5-usbdrd' patches:
>> [PATCH V4 0/5] Add Exynos5 USB 3.0 phy driver based on generic PHY framework
>> http://www.spinics.net/lists/linux-usb/msg105507.html
>>
>>  drivers/phy/phy-exynos5-usbdrd.c |   18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/phy/phy-exynos5-usbdrd.c b/drivers/phy/phy-exynos5-usbdrd.c
>> index ff54a7c..5ca7485 100644
>> --- a/drivers/phy/phy-exynos5-usbdrd.c
>> +++ b/drivers/phy/phy-exynos5-usbdrd.c
>> @@ -18,6 +18,7 @@
>>  #include <linux/module.h>
>>  #include <linux/of.h>
>>  #include <linux/of_address.h>
>> +#include <linux/of_gpio.h>
>>  #include <linux/phy/phy.h>
>>  #include <linux/platform_device.h>
>>  #include <linux/mutex.h>
>> @@ -176,6 +177,7 @@ struct exynos5_usbdrd_phy {
>>       struct clk *ref_clk;
>>       unsigned long ref_rate;
>>       unsigned int refclk_reg;
>> +     int gpio;
>>  };
>>
>>  #define to_usbdrd_phy(inst) \
>> @@ -460,6 +462,9 @@ static int exynos5_usbdrd_phy_power_on(struct phy *phy)
>>       if (!IS_ERR(phy_drd->usb30_sclk))
>>               clk_prepare_enable(phy_drd->usb30_sclk);
>>
>> +     /* Toggle VBUS gpio - on */
>> +     gpio_set_value(phy_drd->gpio, 1);
>> +
>>       /* Power-on PHY*/
>>       inst->phy_cfg->phy_isol(inst, 0);
>>
>> @@ -476,6 +481,9 @@ static int exynos5_usbdrd_phy_power_off(struct phy *phy)
>>       /* Power-off the PHY */
>>       inst->phy_cfg->phy_isol(inst, 1);
>>
>> +     /* Toggle VBUS gpio - off */
>> +     gpio_set_value(phy_drd->gpio, 0);
>> +
>>       if (!IS_ERR(phy_drd->usb30_sclk))
>>               clk_disable_unprepare(phy_drd->usb30_sclk);
>>
>> @@ -585,6 +593,16 @@ static int exynos5_usbdrd_phy_probe(struct platform_device *pdev)
>>
>>       phy_drd->drv_data = drv_data;
>>
>> +     /* Get required GPIO for vbus */
>> +     phy_drd->gpio = of_get_named_gpio(dev->of_node,
>> +                                       "samsung,vbus-gpio", 0);
>
> Is this dt property documented somewhere?
>> +     if (!gpio_is_valid(phy_drd->gpio))
>> +             dev_dbg(dev, "no usbdrd-phy vbus gpio defined\n");
>
> No return here? Can the PHY be functional even without the VBUS?

On few boards, the switch IC's enable may no be controlled by a GPIO,
rather enabled by default.
So in those cases we may not want to stop PHY probe, when the VBUS
GPIO is not present.


-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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