linux-kernel - Re: [PATCH 2/2] cpufreq: cpu0: Extend support beyond CPU0

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Message-ID: <53ACB568.4000903@codeaurora.org>
Date:	Thu, 26 Jun 2014 17:06:00 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Shawn Guo <shawn.guo@...aro.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arvind Chauhan <arvind.chauhan@....com>,
	Mike Turquette <mturquette@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-arm-msm@...r.kernel.org, Sachin Kamat <spk.linux@...il.com>,
	Thomas P Abraham <thomas.ab@...sung.com>,
	Nishanth Menon <nm@...com>, Tomasz Figa <t.figa@...sung.com>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <Mark.Rutland@....com>
Subject: Re: [PATCH 2/2] cpufreq: cpu0: Extend support beyond CPU0

On 06/26/14 03:52, Viresh Kumar wrote:
> On 26 June 2014 00:32, Stephen Boyd <sboyd@...eaurora.org> wrote:
>> I don't think this driver should be using regulator_get_optional() (Mark
>> B. please correct me if I'm wrong). I doubt a supply is actually
>> optional for CPUs, just some DTs aren't specifying them. In those cases,
>> the regulator core will insert a dummy supply and the code will work
>> without having to check for probe defer and error pointers.
> Hi Stephen,
>
> Thanks for your comments.
>
> Leaving the above one, I have tried to fix all you mentioned. And it surely
> looks much better now.
>
> I would like to wait for a day or two before sending V2, as people might
> be reviewing it and the above issue is still wide open..
>
> But in case you wanna test it (completely changed I must say, but
> for good), its here:
>
> git://git.linaro.org/people/viresh.kumar/linux.git cpufreq/cpu0-krait-v2

I gave it a spin. It looks mostly good except for the infinite loop:

diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
index b7ee67c4d1c0..6744321ae33d 100644
--- a/drivers/cpufreq/cpufreq-cpu0.c
+++ b/drivers/cpufreq/cpufreq-cpu0.c
@@ -138,8 +138,10 @@ try_again:
                }
 
                /* Try with "cpu-supply" */
-               if (reg == reg_cpu0)
+               if (reg == reg_cpu0) {
+                       reg = reg_cpu;
                        goto try_again;
+               }
 
                dev_warn(cpu_dev, "failed to get cpu%d regulator: %ld\n",
                         cpu, PTR_ERR(cpu_reg));

and I think we just want reg_cpu to be "cpu", not "cpu-supply" because I
think the regulator core adds in the "-supply" part already.

After fixing that I can get cpufreq going. I'm currently working on
populating the OPPs at runtime without relying on DT. So eventually I'll
need this patch:

diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
index b7ee67c4d1c0..6744321ae33d 100644
--- a/drivers/cpufreq/cpufreq-cpu0.c
+++ b/drivers/cpufreq/cpufreq-cpu0.c
@@ -239,11 +241,6 @@ static int cpu0_cpufreq_init(struct cpufreq_policy *policy)
        }
 
        ret = of_init_opp_table(cpu_dev);
-       if (ret) {
-               dev_err(cpu_dev, "failed to init OPP table: %d\n", ret);
-               goto out_put_node;
-       }
-
        ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
        if (ret) {
                dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);

which I hope is ok.

Finally, checking for equivalent pointers from clk_get() will work now,
but it isn't future-proof if/when the clock framework starts returning
dynamically allocated clock pointers for each clk_get() invocation.
Maybe we need a function in the common clock framework that tells us if
the clocks are the same either via DT or by taking two clock pointers?

-- 
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