linux-kernel - Re: [Patch V3 03/18] phy: tegra: xusb: Add usb-role-switch support

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Date:   Wed, 29 Jan 2020 14:45:38 +0530
From:   Nagarjuna Kristam <nkristam@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>
CC:     <balbi@...nel.org>, <gregkh@...uxfoundation.org>,
        <jonathanh@...dia.com>, <mark.rutland@....com>,
        <robh+dt@...nel.org>, <kishon@...com>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Patch V3 03/18] phy: tegra: xusb: Add usb-role-switch support



On 28-01-2020 23:02, Thierry Reding wrote:
> On Mon, Dec 30, 2019 at 04:39:40PM +0530, Nagarjuna Kristam wrote:
>> If usb-role-switch property is present in USB 2 port, register
>> usb-role-switch to receive usb role changes.
>>
>> Signed-off-by: Nagarjuna Kristam<nkristam@...dia.com>
>> ---
>> V3:
>>   - Driver aborts if usb-role-switch is not added in dt forotg/peripheral
>>     roles.
>>   - Added role name strings instead of enum values in debug prints.
>>   - Updated arguments and variable allignments as per Thierry inputs.
>> ---
>> V2:
>>   - Removed dev_set_drvdata for port->dev.
>>   - Added of_platform_depopulate during error handling and driver removal.
>> ---
>>   drivers/phy/tegra/Kconfig |  1 +
>>   drivers/phy/tegra/xusb.c  | 57 +++++++++++++++++++++++++++++++++++++++++++++++
>>   drivers/phy/tegra/xusb.h  |  3 +++
>>   3 files changed, 61 insertions(+)
>>
>> diff --git a/drivers/phy/tegra/Kconfig b/drivers/phy/tegra/Kconfig
>> index f9817c3..df07c4d 100644
>> --- a/drivers/phy/tegra/Kconfig
>> +++ b/drivers/phy/tegra/Kconfig
>> @@ -2,6 +2,7 @@
>>   config PHY_TEGRA_XUSB
>>   	tristate "NVIDIA Tegra XUSB pad controller driver"
>>   	depends on ARCH_TEGRA
>> +	select USB_CONN_GPIO
>>   	help
>>   	  Choose this option if you have an NVIDIA Tegra SoC.
>>   
>> diff --git a/drivers/phy/tegra/xusb.c b/drivers/phy/tegra/xusb.c
>> index f98ec39..11ea9b5 100644
>> --- a/drivers/phy/tegra/xusb.c
>> +++ b/drivers/phy/tegra/xusb.c
>> @@ -523,6 +523,7 @@ static int tegra_xusb_port_init(struct tegra_xusb_port *port,
>>   	port->dev.type = &tegra_xusb_port_type;
>>   	port->dev.of_node = of_node_get(np);
>>   	port->dev.parent = padctl->dev;
>> +	port->dev.driver = padctl->dev->driver;
> This looks wrong. I don't think driver's are supposed to set this
> because it basically means that the device is being attached to the
> driver, but in this case it doesn't get probed by the driver and in
> fact the ports don't match the pad controller, so they can't really
> be driven by the same driver.
> 
> Is there any particular reason why you need this?
> 
> Thierry

Yes, port->dev.driver->owner is accessed in USB role switch driver in 
API usb_role_switch_get. If driver param is not updated, it causes NULL 
pointer exception. Based on your inputs, since this assignment is not 
supposed to used, I believe option available is to create a new 
device_driver structure and assign the same here.
Please share your thoughts.

- Nagarjuna