linux-kernel - Re: [PATCH v6 1/9] drivers: phy: add generic PHY framework

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Date:	Wed, 5 Jun 2013 10:55:58 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Sylwester Nawrocki <s.nawrocki@...sung.com>
CC:	<grant.likely@...aro.org>, <tony@...mide.com>, <balbi@...com>,
	<arnd@...db.de>, <swarren@...dia.com>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-usb@...r.kernel.org>, <rob.herring@...xeda.com>,
	<rob@...dley.net>, <b-cousson@...com>, <linux@....linux.org.uk>,
	<gregkh@...uxfoundation.org>, <benoit.cousson@...aro.org>,
	<mchehab@...hat.com>, <akpm@...ux-foundation.org>,
	<cesarb@...arb.net>, <davem@...emloft.net>, <rnayak@...com>,
	<shawn.guo@...aro.org>, <santosh.shilimkar@...com>,
	<devicetree-discuss@...ts.ozlabs.org>, <linux-doc@...r.kernel.org>,
	<nsekhar@...com>
Subject: Re: [PATCH v6 1/9] drivers: phy: add generic PHY framework

Hi,

On Tuesday 04 June 2013 07:13 PM, Sylwester Nawrocki wrote:
> Hi,
>
> On 06/04/2013 02:26 PM, Kishon Vijay Abraham I wrote:
>>>> +static inline int phy_init(struct phy *phy)
>>>> +{
>>>> +	pm_runtime_get_sync(&phy->dev);
>>>
>>> Hmm, no need to check return value here ? Also it looks a bit unexpected to
>>
>> I purposely dint check the return values in order to support platforms
>> that don’t enable pm_runtime.
>
> Then I guess this should be called conditionally and any errors returned
> if runtime PM is enabled ? Not sure if pm_runtime_enabled() would be
> helpful such situation.
Indeed. I think it can be used.
>
>>> possibly have runtime_resume callback of a PHY device called before ops->init()
>>> call ? It seems a bit unclear what the purpose of init() callback is.
>>
>> Not really. Anything that is used to initialize the PHY (internal
>> configuration) can go in phy_init. Usually in runtime_resume callback,
>> optional functional clocks are enabled and also in some cases context
>> restore is done. So it really makes sense to enable clocks/module
>> (pm_runtime_get_sync) before doing a PHY configuration (phy_init).
>
> OK, that makes sense. All PHY device resources must be prepared anyway
> before a PHY object is registered with the PHY core.
>
>>>> +	if (phy->ops->init)
>>>> +		return phy->ops->init(phy);
>>>> +
>>>> +	return -EINVAL;
>>>> +}
>>>> +
>>>> +static inline int phy_exit(struct phy *phy)
>>>> +{
>>>> +	int ret = -EINVAL;
>>>> +
>>>> +	if (phy->ops->exit)
>>>> +		ret = phy->ops->exit(phy);
>>>> +
>>>> +	pm_runtime_put_sync(&phy->dev);
>>>> +
>>>> +	return ret;
>>>> +}
>>>
>>> Do phy_init/phy_exit need to be mandatory ? What if there is really
>>
>> No. phy_init/phy_exit is not mandatory at all.
>>> nothing to do in those callbacks ? Perhaps -ENOIOCTLCMD should be
>>> returned if a callback is not implemented, so PHY users can recognize
>>> such situation and proceed ?
>>
>> So currently these APIs return -EINVAL if these callbacks are not
>> populated which is good enough IMHO.
>
> But -EINVAL could be well returned from the callback function. Perhaps
> ENOTSUPP could be used instead ?

hmm.. could be..

Thanks
Kishon
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