linux-kernel - Re: [RFC v5 07/15] usb: ehci: add vbus-gpio parameter

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Message-ID: <56C60DF8.1060809@cogentembedded.com>
Date:	Thu, 18 Feb 2016 21:31:20 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Antony Pavlov <antonynpavlov@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Marek Vasut <marex@...x.de>
Cc:	linux-mips@...ux-mips.org, Wills Wang <wills.wang@...e.com>,
	Daniel Schwierzeck <daniel.schwierzeck@...il.com>,
	Alban Bedel <albeu@...e.fr>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v5 07/15] usb: ehci: add vbus-gpio parameter

On 02/18/2016 09:06 PM, Antony Pavlov wrote:

>>> This patch retrieves and configures the vbus control gpio via
>>> the device tree.
>>>
>>> This patch is based on a ehci-s5p.c commit fd81d59c90d38661
>>> ("USB: ehci-s5p: Add vbus setup function to the s5p ehci glue layer").
>>>
>>> Signed-off-by: Antony Pavlov <antonynpavlov@...il.com>
>>> Cc: Alan Stern <stern@...land.harvard.edu>
>>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>> Cc: linux-usb@...r.kernel.org
>>> Cc: linux-kernel@...r.kernel.org
>>> ---
>>>   drivers/usb/host/ehci-platform.c | 22 ++++++++++++++++++++++
>>>   1 file changed, 22 insertions(+)
>>>
>>> diff --git a/drivers/usb/host/ehci-platform.c b/drivers/usb/host/ehci-platform.c
>>> index bd7082f2..0d95ced 100644
>>> --- a/drivers/usb/host/ehci-platform.c
>>> +++ b/drivers/usb/host/ehci-platform.c
>>> @@ -28,6 +28,7 @@
>>>   #include <linux/io.h>
>>>   #include <linux/module.h>
>>>   #include <linux/of.h>
>>> +#include <linux/of_gpio.h>
>>>   #include <linux/phy/phy.h>
>>>   #include <linux/platform_device.h>
>>>   #include <linux/reset.h>
>>> @@ -142,6 +143,25 @@ static struct usb_ehci_pdata ehci_platform_defaults = {
>>>   	.power_off =		ehci_platform_power_off,
>>>   };
>>>
>>> +static void setup_vbus_gpio(struct device *dev)
>>> +{
>>> +	int err;
>>> +	int gpio;
>>> +
>>> +	if (!dev->of_node)
>>> +		return;
>>> +
>>> +	gpio = of_get_named_gpio(dev->of_node, "vbus-gpio", 0);
>>> +	if (!gpio_is_valid(gpio))
>>> +		return;
>>> +
>>> +	err = devm_gpio_request_one(dev, gpio,
>>> +				GPIOF_OUT_INIT_HIGH | GPIOF_EXPORT_DIR_FIXED,
>>> +				"ehci_vbus_gpio");
>>> +	if (err)
>>> +		dev_err(dev, "can't request ehci vbus gpio %d", gpio);
>>
>>
>> I don't understand this.  If you get an error here, what's the point of
>> allowing the probe to continue?  Shouldn't you return an error code so
>> the probe will fail?
>
> Please ignore the 'usb: ehci: add vbus-gpio parameter' patch!
>
> In the new AR9331 patchseries I use chipidea USB driver (thanks to Marek for the suggestion)
> in the AR9331 dtsi-file:
>
>          usb: usb@...00100 {
>                  compatible = "chipidea,usb2";
>                  reg = <0x1b000000 0x200>;
>
>                  interrupt-parent = <&cpuintc>;
>                  interrupts = <3>;
>                  resets = <&rst 5>;
>
>                  phy-names = "usb-phy";
>                  phys = <&usb_phy>;
>
>                  status = "disabled";
>          };
>
>
> so I use regulator in the TL-MR3020 board dts file:
>
>          reg_usb_vbus: reg_usb_vbus {
>                  compatible = "regulator-fixed";
>                  regulator-name = "usb_vbus";
>                  regulator-min-microvolt = <5000000>;

    Not 0?

>                  regulator-max-microvolt = <5000000>;
>                  gpio = <&gpio 8 GPIO_ACTIVE_HIGH>;

    Where's the switch if both voltages are equal?

>                  enable-active-high;
>          };
>
> &usb {
>          dr_mode = "host";
>          vbus-supply = <&reg_usb_vbus>;
>          status = "okay";
> };
>
> As a result there is no need in adding vbus-gpio parameter to ehci anymore!
[...]

MBR, Sergei