linux-kernel - Re: [PATCH 2/3] mfd: tps65090: Stop caching registers

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Date:	Wed, 16 Apr 2014 11:27:25 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Lee Jones <lee.jones@...aro.org>,
	Anton Vorontsov <anton@...msg.org>,
	Olof Johansson <olof@...om.net>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	AJAY KUMAR RAMAKRISHNA SHYMALAMMA <ajaykumar.rs@...sung.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] mfd: tps65090: Stop caching registers

Mark,

On Wed, Apr 16, 2014 at 3:13 AM, Mark Brown <broonie@...nel.org> wrote:
> On Wed, Apr 16, 2014 at 10:59:22AM +0100, Lee Jones wrote:
>
>> > NOTE: the IRQnMASK and CG_CTRLn registers are the exception and could
>> > be cached.  If we find that we spend a lot of time reading those we
>> > can turn on cache for just those registers.
>
>> > -static bool is_volatile_reg(struct device *dev, unsigned int reg)
>> > -{
>> > -   if ((reg == TPS65090_INT_STS) || (reg == TPS65090_INT_STS2))
>> > -           return true;
>> > -   else
>> > -           return false;
>> > -}
>> > -
>
>> I don't know enough about Regmap internals to know what this actually
>> affects in real terms.
>
>> Mark,
>>   Does this change seem sane to you?
>
> It does what it says, it stops us caching stuff.  It would seem better
> to do what the changelog suggests above and keep caching the registers
> that can be cached - especially the interrupt masks, they should get
> read in the interrupt path and that tends to be a bit latency sensitive.

Done
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