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

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Message-ID: <556C7770.70506@intel.com>
Date:	Mon, 01 Jun 2015 18:17:04 +0300
From:	Mathias Nyman <mathias.nyman@...el.com>
To:	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>,
	Roger Quadros <rogerq@...com>
Subject: Re: [PATCH 3/6] xhci: probe phy before add usb_hcd

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.

-Mathias
 

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