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

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Message-id: <51ADEEF6.1030200@samsung.com>
Date:	Tue, 04 Jun 2013 15:43:18 +0200
From:	Sylwester Nawrocki <s.nawrocki@...sung.com>
To:	Kishon Vijay Abraham I <kishon@...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 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.

>> 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 ?


Thanks,
Sylwester
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