linux-kernel - Re: [PATCH 2/5 v11] arm: omap: usb: ehci and ohci hwmod structures for omap3

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Date:	Tue, 4 Oct 2011 17:25:34 +0530
From:	"Munegowda, Keshava" <keshava_mgowda@...com>
To:	Paul Walmsley <paul@...an.com>
Cc:	Benoit Cousson <b-cousson@...com>, parthab@...ia.ti.com,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, balbi@...com, gadiyar@...com,
	sameo@...ux.intel.com, tony@...mide.com, khilman@...com,
	johnstul@...ibm.com, vishwanath.bs@...com
Subject: Re: [PATCH 2/5 v11] arm: omap: usb: ehci and ohci hwmod structures
 for omap3

On Fri, Sep 30, 2011 at 11:46 PM, Paul Walmsley <paul@...an.com> wrote:
> On Fri, 30 Sep 2011, Munegowda, Keshava wrote:
>
>> On Fri, Sep 30, 2011 at 2:02 PM, Paul Walmsley <paul@...an.com> wrote:
>> > On Wed, 28 Sep 2011, Munegowda, Keshava wrote:
>> >
>> >> Thanks paul,
>> >>
>> >> But In USB Host case, there is a challenge!
>> >>
>> >> I need both usbhost_48m_fck and usbhost_120m_fck to be turned on when
>> >> I invoke pm_runtime_get_sync ; so there are couple of options to do this
>> >>
>> >> 1. use clk_get with hard coded  usbhost_120m_fck name in  usbhs driver
>> >>        enable this clock after invoking pm_runtime_get_sync
>> >>
>> >> 2. add an additional flag in hwmod ; so that pm_runtime_get_sync will enable
>> >>            main clock as well as optional clocks
>> >>
>> >> please comment on these two approaches..
>> >
>> > Looks like you picked approach #1 which is fine with me.
>> >
>> > Here's what I don't understand about how this clock is used, though.
>> > According to the 34xx TRM vZR Section 24.2.3.1.2 "High-Speed USB Host
>> > Subsystem Clocks", this is only used to "clock EHCI controller internal
>> > logic".  So if EHCI is not being used, it would seem to me that this clock
>> > shouldn't be enabled?  But patch #5 seems to enable and disable it
>> > unconditionally.  Am I missing something here?
>>
>> OK. are you suggesting that this clock should be enabled/disabled; only
>> if atleast one port is selected for ehci?
>
> Seems to make sense to me?  If the clock really isn't needed for OHCI,
> then it shouldn't be enabled when only OHCI is in use?

thanks. I will make this :-)

regards
keshava
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