linux-kernel - Re: [RFC] usb issue on imx27: 3 clocks are needed

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Message-ID: <20140818092635.GI2114@dragon>
Date:	Mon, 18 Aug 2014 17:26:37 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Peter Chen <peter.chen@...escale.com>
CC:	Philippe Reynes <tremyfr@...il.com>,
	<Linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	<gwenhael.goavec-merou@...bucayre.com>
Subject: Re: [RFC] usb issue on imx27: 3 clocks are needed

On Mon, Aug 18, 2014 at 05:00:59PM +0800, Peter Chen wrote:
> On Sat, Aug 16, 2014 at 05:38:30PM +0200, Philippe Reynes wrote:
> > Hi all,
> > 
> > i.MX27's usb needs three clocks (usb_ipg_gate, usb_ahb_gate and usb_div)
> > but the current chipidea driver implementation, and devicetree, provides
> > only ipg and ahb. Consequently, if the bootloader don't enable the last
> > one, the kernel will crash.
> > 
> > Our approach/idea is to add a second, optionnal, clock in ci_hdrc_imx.c
> > with 'per' name in devicetree  and to add  clock name 'main_clk' for mandatory clock.
> > This approach it correct? Or an other approach seems better?
> > Thank you very much for your point of view.
> > 
> 
> It is ok for me to have ipg, ahb and per clocks at driver, but how can you maintain
> DT consistent?

Adding new clock as optional one will just maintain the DT
compatibility.

> Can you accept open ipg and per always on at clock.c?

No, usb driver should manage its clocks.

Shawn
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