linux-kernel - Re: [PATCH 6/6 v6] cpufreq, highbank: add support for highbank cpufreq

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Message-ID: <50B60E9C.9000405@calxeda.com>
Date:	Wed, 28 Nov 2012 07:16:12 -0600
From:	Mark Langsdorf <mark.langsdorf@...xeda.com>
To:	Shawn Guo <shawn.guo@...aro.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH 6/6 v6] cpufreq, highbank: add support for highbank cpufreq

On 11/27/2012 08:32 PM, Shawn Guo wrote:
> On Tue, Nov 27, 2012 at 02:04:32PM -0600, Mark Langsdorf wrote:
>> Highbank processors depend on the external ECME to perform voltage
>> management based on a requested frequency. Communication between the
>> A9 cores and the ECME happens over the pl320 IPC channel.
> 
> ...
> 
>> +static int hb_voltage_change(unsigned int freq)
>> +{
>> +	int i;
>> +	u32 msg[7];
>> +
>> +	msg[0] = HB_CPUFREQ_CHANGE_NOTE;
>> +	msg[1] = freq / 1000;
>> +	for (i = 2; i < 7; i++)
>> +		msg[i] = 0;
>> +
>> +	return pl320_ipc_transmit(msg);
> 
> Is it possible to have this handled inside clk_set_rate() call of cpu
> clock?

Standard practice is to have cpufreq_set_target() handle voltage
transitions and leave clk_set_rate() handle the frequency changes. I'd
have to move most of the logic of hb_set_target() into
clk_highbank.c:clk_pll_set_rate() and then add extra logic for when
cpufreq is not enabled/loaded. I don't think the clk maintainers would
take that patch, either.

So no.

--Mark Langsdorf
Calxeda, Inc.

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