Thread (48 messages) 48 messages, 7 authors, 2017-09-06

[PATCH v2 17/18] cpufreq: add support for CPU DVFS based on SCMI message protocol

From: viresh.kumar@linaro.org (Viresh Kumar)
Date: 2017-08-09 10:06:58
Also in: linux-devicetree, linux-pm, lkml

On 09-08-17, 10:59, Sudeep Holla wrote:
On 09/08/17 05:18, Viresh Kumar wrote:
quoted
This stores the same handle pointer which is stored in the global variable
below. Right? Why keep a local variable here at all ?
Yes, you are right. Initially, started with just private pointers and
then added global. I was thinking of calling devm_scmi_handle_get per
policy to reflect the refcount correctly and drop global variable. Let
me know what you think.
A refcount of 1 should be fine as well, i.e. For the cpufreq driver. Why would
SCMI care if we manage multiple policies here ? Unless it makes something within
SCMI core better.
quoted
This is something special which is used only when we are returning indexes and
I am not sure if this will have benefit here. I will rather return 0 here.
That's what other drivers are doing.
Indeed had 0 initially but changed as per Juri's suggestion.
Maybe he suggested doing that in the fast switch routine ? As that's the normal
protocol there. Though I have sent a patch today to propose using 0 there as
well (you cc'd).
But is 0
treated as failure and still running at current OPP ?
You have used that in the ->get() routine. So the OPP isn't changing, but we are
just trying to fetch it. cpufreq core doesn't do a lot with the value returned
from here, but at one place we break early if 0 is returned. And so all drivers
are returning that.
and not 0KHz I assume.
Yeah, 0 KHz is dead CPU really :)
quoted
I suppose any CPU can change the frequency of any other CPU here, right? You
must set policy->dvfs_possible_from_any_cpu = true, from ->init() then.
OK, I missed to see something like that exists, will do.
Fairly recent stuff, present in pm/linux-next only.
quoted
quoted
+	/*
+	 * But we need OPP table to function so if it is not there let's
+	 * give platform code chance to provide it for us.
+	 */
How are we getting the OPPs? DT or non DT ?
Non DT :), from the firmware.
I would improve the above comment in that case to clearly say that OPPs are
added by the platform, lets wait for it.

-- 
viresh
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