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

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Date:   Mon, 23 Dec 2019 06:40:01 +0000
From:   Peter Chen <peter.chen@....com>
To:     Dmitry Osipenko <digetx@...il.com>
CC:     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

On 19-12-20 07:31:08, Dmitry Osipenko wrote:
> 20.12.2019 06:56, Peter Chen пишет:
> > On 19-12-20 04:52:38, Dmitry Osipenko wrote:
> >> Now, when ci_hdrc_tegra kernel module is loaded, the phy_tegra_usb module
> >> is loaded too regardless of kernel's configuration. Previously this
> >> problem was masked because Tegra's EHCI driver is usually enabled in
> >> kernel's config and thus PHY driver was getting loaded because of it, but
> >> now I was making some more thorough testing and noticed that PHY's module
> >> isn't getting auto-loaded without the host driver.
> >>
> >> Note that ChipIdea's driver doesn't use any of the exported functions of
> >> phy_tegra_usb module and thus the module needs to be requested explicitly.
> >>
> >> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> >> ---
> >>  drivers/usb/chipidea/Kconfig         | 1 +
> >>  drivers/usb/chipidea/ci_hdrc_tegra.c | 6 ++++++
> >>  2 files changed, 7 insertions(+)
> >>
> >> diff --git a/drivers/usb/chipidea/Kconfig b/drivers/usb/chipidea/Kconfig
> >> index ae850b3fddf2..d53db520e209 100644
> >> --- a/drivers/usb/chipidea/Kconfig
> >> +++ b/drivers/usb/chipidea/Kconfig
> >> @@ -7,6 +7,7 @@ config USB_CHIPIDEA
> >>  	select RESET_CONTROLLER
> >>  	select USB_ULPI_BUS
> >>  	select USB_ROLE_SWITCH
> >> +	select USB_TEGRA_PHY if ARCH_TEGRA
> >>  	help
> >>  	  Say Y here if your system has a dual role high speed USB
> >>  	  controller based on ChipIdea silicon IP. It supports:
> >> diff --git a/drivers/usb/chipidea/ci_hdrc_tegra.c b/drivers/usb/chipidea/ci_hdrc_tegra.c
> >> index 7455df0ede49..8bc11100245d 100644
> >> --- 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.
> 
> So if you'll do:
> 
> # rmmod ci_hdrc_tegra; rmmod ci_hdrc; rmmod phy_tegra_usb;
> # modprobe ci_hdrc_tegra
> # lsmod
> Module                  Size  Used by
> ci_hdrc_tegra          16384  0
> ci_hdrc                45056  1 ci_hdrc_tegra
> 
> After this patch:
> 
> # rmmod ci_hdrc_tegra; rmmod ci_hdrc; rmmod phy_tegra_usb;
> # modprobe ci_hdrc_tegra
> # lsmod
> Module                  Size  Used by
> Module                  Size  Used by
> phy_tegra_usb          20480  1
> ci_hdrc_tegra          16384  0
> ci_hdrc                45056  1 ci_hdrc_tegra

I wonder why the driver needs such dependency? If there are two phy
drivers could work with this controller driver, you may request two
modules. Doesn't such dependency should be done by the board
level script? Do you know are there any other drivers do such things?

-- 

Thanks,
Peter Chen