linux-kernel - Re: [PATCH v2 10/10] usb: chipidea: tegra: Add USB_TEGRA

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Date:   Thu, 2 Jan 2020 18:17:47 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     Peter Chen <peter.chen@....com>, Rob Herring <robh-dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Felipe Balbi <balbi@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 10/10] usb: chipidea: tegra: Add USB_TEGRA_PHY module
 to driver's dependencies

31.12.2019 00:02, Michał Mirosław пишет:
> On Tue, Dec 24, 2019 at 07:21:05AM +0300, Dmitry Osipenko wrote:
>> 24.12.2019 00:32, Michał Mirosław пишет:
>>> On Fri, Dec 20, 2019 at 07:31:08AM +0300, Dmitry Osipenko wrote:
>>>> 20.12.2019 06:56, Peter Chen пишет:
>>>>> On 19-12-20 04:52:38, Dmitry Osipenko wrote:
>>> [...]
>>>>>> --- a/drivers/usb/chipidea/ci_hdrc_tegra.c
>>>>>> +++ b/drivers/usb/chipidea/ci_hdrc_tegra.c
>>>>>> @@ -53,6 +53,12 @@ static int tegra_udc_probe(struct platform_device *pdev)
>>>>>>  	struct tegra_udc *udc;
>>>>>>  	int err;
>>>>>>  
>>>>>> +	if (IS_MODULE(CONFIG_USB_TEGRA_PHY)) {
>>>>>> +		err = request_module("phy_tegra_usb");
>>>>>> +		if (err)
>>>>>> +			return err;
>>>>>> +	}
>>>>>> +
>>>>>
>>>>> Why you do this dependency, if this controller driver can't
>>>>> get USB PHY, it should return error. What's the return value
>>>>> after calling below:
>>>>>
>>>>> 	udc->phy = devm_usb_get_phy_by_phandle(&pdev->dev, "nvidia,phy", 0);
>>>>
>>>> It returns -EPROBE_DEFER when phy_tegra_usb isn't loaded.
>>>
>>> How are other driver modules autoloaded? Isn't there an appropriate
>>> MODALIAS or MODULE_DEVICE_TABLE in there?
>>
>> Hello Michał,
>>
>> The phy_tegra_usb module is fine by itself, it's getting autoloaded.
>>
>> The problem is that ci_hdrc_tegra module depends on the phy_tegra_usb
>> module and thus the PHY module should be loaded before the CI module,
>> otherwise CI driver fails with the EPROBE_DEFER.
> 
> Why, then, is CI driver not being probed again after PHY driver loads?
> EPROBE_DEFER is what should cause driver core to re-probe a device after
> other devices appear (PHY in this case).

CI driver is getting re-probed just fine if PHY's driver module is
loaded manually after loading the CI's module. This patch removes this
necessity to manually load PHY's module.

This is just a minor convenience change that brings the CI's driver
loading behaviour on par with the behaviour of loading Tegra's EHCI
driver module.