linux-kernel - Re: [PATCH v5 2/2] usb: chipidea: imx: Add binding to disable USB 60Mhz clock

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Date:   Mon, 26 Sep 2016 10:54:52 +0200
From:   Fabien Lahoudere <fabien.lahoudere@...labora.co.uk>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     Peter.Chen@....com, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, robh+dt@...nel.org,
        mark.rutland@....com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] usb: chipidea: imx: Add binding to disable USB
 60Mhz clock

Hi,

On 26/09/16 10:18, Sascha Hauer wrote:
> On Wed, Sep 21, 2016 at 11:07:07AM +0200, Fabien Lahoudere wrote:
>> This binding allow to disable the internal 60Mhz clock for USB host2 or
>> host3.
>>
>> Signed-off-by: Fabien Lahoudere <fabien.lahoudere@...labora.co.uk>
>> ---
>>  Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt |  1 +
>>  drivers/usb/chipidea/ci_hdrc_imx.c                     |  2 ++
>>  drivers/usb/chipidea/ci_hdrc_imx.h                     |  1 +
>>  drivers/usb/chipidea/usbmisc_imx.c                     | 13 +++++++++++++
>>  4 files changed, 17 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
>> index 0e03344..f83da66 100644
>> --- a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
>> +++ b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
>> @@ -84,6 +84,7 @@ i.mx specific properties
>>  - over-current-active-high: over current signal polarity is high active,
>>    typically over current signal polarity is low active.
>>  - external-vbus-divider: enables off-chip resistor divider for Vbus
>> +- disable-int60ck: disable internal 60MHz clock for usb host2 or host3 on imx53
>
> Why do we need a binding for this? I would assume the driver should know
> whether this clock is in use or not. If it doesn't that's a problem we
> should solve.
>

Yes you are right because we can disable this clock for OTG and with 
ULPI PHY. I think that it will be better to have a dt binding but if it 
is useless I can remove it and disable clock when ULPI mode is enabled.

> Sascha
>

Fabien