linux-kernel - Re: [PATCH 3/6] xhci: probe phy before add usb

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Message-ID: <556D2A6E.4070802@ti.com>
Date:	Tue, 2 Jun 2015 07:00:46 +0300
From:	Roger Quadros <rogerq@...com>
To:	Mathias Nyman <mathias.nyman@...el.com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>, <balbi@...com>
CC:	<chunfeng.yun@...iatek.com>, Mark Rutland <mark.rutland@....com>,
	<devicetree@...r.kernel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	<linux-mediatek@...ts.infradead.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 3/6] xhci: probe phy before add usb_hcd

Mathias.

On 01/06/15 18:17, Mathias Nyman wrote:
> On 01.06.2015 17:52, Yingjoe Chen wrote:
>> On Wed, 2015-05-27 at 07:18 -0500, Felipe Balbi wrote:
>>> On Wed, May 27, 2015 at 07:48:00PM +0800, chunfeng.yun@...iatek.com wrote:
>>>> From: Chunfeng Yun <chunfeng.yun@...iatek.com>
>>>>
>>>> find the phy driver before add primary usb_hcd to avoid acessing
>>>> xHCI register which may hangup the system when the phy is not loaded
>>>> yet and the related powers or clocks put in phy driver are not
>>>> enabled.
>>>
>>> it seems like the same clock is needed by PHY and XHCI. This patch looks
>>> incorrect.
>>
>>
>> Hi,
>>
>> I agree that the driver should enable clock it used by itself and not
>> depends on init order. This should be fixed.
>>
>> But in general, I think it make sense to only add hcd after all required
>> resource are ready. At least it remove unnecessary calls to
>> usb_add_hcd/usb_remove_hcd. Is it better if the commit message is
>> changed to something like the below?
>>
>> Currently xhci_plat_probe() call usb_add_hcd before trying to init the
>> phy. However if the phy is not ready at the moment, it have to remove
>> the hcd and probe again later
>>
>> Change the init order so we only add hcd when all required resource are
>> ready.
>>
> Hi
>
> Rogers Quadros patchseries that changes how HCDs are created and added for
> xhci-plat was just sent forward. It first creates both HCDs, then adds them.
>
> Doesn't usb_add_hcd() as it's first task take care of the PHYs?
> I'm hoping to remove that part completely from xhci-plat.c but haven't
> looked into it properly yet.
>

usb_add_hcd() does

         if (IS_ENABLED(CONFIG_USB_PHY) && !hcd->usb_phy) {
                 struct usb_phy *phy = usb_get_phy_dev(hcd->self.controller, 0);
...
         if (IS_ENABLED(CONFIG_GENERIC_PHY) && !hcd->phy) {
                 struct phy *phy = phy_get(hcd->self.controller, "usb");
...

but xhci-plat.c does
	hcd->usb_phy = devm_usb_get_phy_by_phandle(&pdev->dev, "usb-phy", 0);


So there needs to be some alignment.

cheers,
-roger
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