linux-kernel - Re: [linux-pm] [PATCH] opp: introduce library for device-specific OPPs

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Date:	Fri, 17 Sep 2010 10:53:06 -0500
From:	Nishanth Menon <nm@...com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Phil Carmody <ext-phil.2.carmody@...ia.com>,
	linux-doc <linux-doc@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Chikkature Rajashekar, Madhusudhan" <madhu.cr@...com>,
	"Aguirre, Sergio" <saaguirre@...com>,
	Andi Kleen <ak@...ux.intel.com>,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	Matthew Garrett <mjg@...hat.com>,
	Len Brown <len.brown@...el.com>,
	Eduardo Valentin <eduardo.valentin@...ia.com>,
	linux-omap <linux-omap@...r.kernel.org>,
	"Gopinath, Thara" <thara@...com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	"Granados Dorado, Roberto" <x0095451@...com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Romit Dasgupta <ro.mit@...com>,
	Tero Kristo <Tero.Kristo@...ia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Premi, Sanjeev" <premi@...com>
Subject: Re: [linux-pm] [PATCH] opp: introduce library for device-specific
 OPPs

Mark Brown had written, on 09/17/2010 10:36 AM, the following:
> On Thu, Sep 16, 2010 at 08:29:33PM -0500, Nishanth Menon wrote:
> 
>> +struct opp_def {
>> +	unsigned long freq;
>> +	unsigned long u_volt;
>> +
>> +	bool enabled;
>> +};
> 
> It might be clearer to use some term other than enabled in the code -
> when reading I wasn't immediately sure if enabled meant that it was
> available to be selected or if it was the active operating point.  How
> about 'allowed' (though I'm not 100% happy with that)?
;).. The opp is enabled or disabled if it is populated, it is implicit 
as being available but not enabled- how about active? this would change 
the opp_enable/disable functions to opp_activate, opp_deactivate..

Recommendations folks?

> 
>> +static inline int opp_add(struct device *dev, const struct opp_def *opp_def)
>> +{
>> +	return ERR_PTR(-EINVAL);
>> +}
> 
> Mismatch with the return type and value here.
/me kicks himself.. ouch.. thanks.. will fix in v2.

> 
>> +/**
>> + * opp_enable() - Enable a specific OPP
>> + * @opp:	Pointer to opp
>> + *
>> + * Enables a provided opp. If the operation is valid, this returns 0, else the
>> + * corresponding error value.
>> + *
>> + * OPP used here is from the the opp_is_valid/opp_has_freq or other search
>> + * functions
>> + */
>> +int opp_enable(struct opp *opp)
>> +{
>> +	if (unlikely(!opp || IS_ERR(opp))) {
>> +		pr_err("%s: Invalid parameters being passed\n", __func__);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (!opp->enabled && opp->dev_opp)
>> +		opp->dev_opp->enabled_opp_count++;
>> +
>> +	opp->enabled = true;
>> +
>> +	return 0;
>> +}
> 
> When reading the description I'd expected to see some facility to
> trigger selection of an active operating point in the library (possibly
> as a separate call since you might have a bunch of operating points
> being updated in quick succession) but it looks like that needs to be
> supplied externally at the minute?
The intent is we use the opp_search* functions to pick up the opp and 
enable/activate it and disable/deactivate it.

-- 
Regards,
Nishanth Menon
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