From: Stephen Boyd <sboyd@codeaurora.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
nm@ti.com
Subject: Re: [PATCH V2 00/16] PM / OPP: Introduce APIs to transition OPPs
Date: Mon, 1 Feb 2016 11:41:26 -0800 [thread overview]
Message-ID: <20160201194126.GJ4848@codeaurora.org> (raw)
In-Reply-To: <20160201040857.GB13476@vireshk>
On 02/01, Viresh Kumar wrote:
> On 29-01-16, 17:48, Stephen Boyd wrote:
> > Just a note for future work, I think we're going to need to add
> > some sort of enable/disable into the OPP layer. At least in qcom
> > designs, if a clock is off we don't want the voltage requirement
> > for that clock to factor into the final voltage on the regulator.
> > Furthermore, we want to disable the regulator with
> > regulator_disable() if all the clocks are off.
>
> Hmm, we need to discuss more on this, maybe in a HO sometime or at
> connect :)
Sure.
>
> > This is also a problem with cpufreq-dt. The regulators and clocks
> > are assumed to be enabled out of the bootloader, which may not
> > even be true. Now that OPP layer is managing all the clocks and
> > regulators here we're going to need to do something to make sure
> > they're on and controllable.
>
> Also, I fail to understand, how the clock of a 'online' CPU can be
> off?
>
Hmm right. The problem is the clock and regulator frameworks
aren't aware that they're enabled already. In the case of the
clocks, if we switch a mux from one source to another while
frequency switching and the framework doesn't know the clock is
on, it won't turn on the new source for the CPU, effectively
killing the CPU.
In the regulator case I ran into a problem with qcom's RPM
regulator implementation where the voltage isn't sent when the
regulator is disabled (the driver has some check for that case).
I suppose in both cases these could be fixed in the frameworks if
they detected on/off state at boot. That's fine, but it doesn't
seem like that will work for things like GPU where the clock may
not be on in the first place. If we don't want to clk_get() and
regulator_get() in two places (OPP and drivers) then we'll need
on/off in OPP code.
In the CPU case, we've turned clocks on and off when CPUs are
hotplugged in and out on qcom platforms so that we can drop the
clock and voltage requirements of a particular CPU. If we had
that CPU driver on ARM platforms it would be similar to the GPU
case then. We could get the clocks and regulators in two places
and we could put the clock/regulator on/off code in the CPU
driver instead of the OPP layer.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
prev parent reply other threads:[~2016-02-01 19:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 8:20 [PATCH V2 00/16] PM / OPP: Introduce APIs to transition OPPs Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 01/16] PM / OPP: get/put regulators from OPP core Viresh Kumar
2016-02-02 2:29 ` Stephen Boyd
2016-02-02 3:23 ` Viresh Kumar
2016-02-08 22:52 ` Stephen Boyd
2016-02-09 3:53 ` Viresh Kumar
2016-02-09 3:54 ` Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 02/16] PM / OPP: Disable OPPs that aren't supported by the regulator Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 03/16] PM / OPP: Introduce dev_pm_opp_get_max_volt_latency() Viresh Kumar
2016-02-02 2:30 ` Stephen Boyd
2016-01-28 8:20 ` [PATCH V2 04/16] PM / OPP: Introduce dev_pm_opp_get_max_transition_latency() Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 05/16] PM / OPP: Parse clock-latency and voltage-tolerance for v1 bindings Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 06/16] PM / OPP: Manage device clk Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 07/16] PM / OPP: Add dev_pm_opp_set_rate() Viresh Kumar
2016-02-02 2:10 ` Stephen Boyd
2016-02-02 3:38 ` Viresh Kumar
2016-02-02 20:46 ` Stephen Boyd
2016-01-28 8:20 ` [PATCH V2 08/16] cpufreq: dt: Convert few pr_debug/err() calls to dev_dbg/err() Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 09/16] cpufreq: dt: Rename 'need_update' to 'opp_v1' Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 10/16] cpufreq: dt: OPP layers handles clock-latency for V1 bindings as well Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 11/16] cpufreq: dt: Pass regulator name to the OPP core Viresh Kumar
2016-02-02 2:34 ` Stephen Boyd
2016-02-02 6:10 ` Viresh Kumar
2016-02-08 22:55 ` Stephen Boyd
2016-02-09 4:10 ` Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 12/16] cpufreq: dt: Unsupported OPPs are already disabled Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 13/16] cpufreq: dt: Reuse dev_pm_opp_get_max_transition_latency() Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 14/16] cpufreq: dt: Use dev_pm_opp_set_rate() to switch frequency Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 15/16] cpufreq: dt: drop references to DT node Viresh Kumar
2016-02-02 6:11 ` Viresh Kumar
2016-02-08 22:56 ` Stephen Boyd
2016-02-09 4:22 ` Viresh Kumar
2016-01-28 8:20 ` [PATCH V2 16/16] cpufreq: dt: No need to allocate resources anymore Viresh Kumar
2016-02-02 6:12 ` Viresh Kumar
2016-02-08 22:58 ` Stephen Boyd
2016-01-30 1:48 ` [PATCH V2 00/16] PM / OPP: Introduce APIs to transition OPPs Stephen Boyd
2016-02-01 4:08 ` Viresh Kumar
2016-02-01 19:41 ` Stephen Boyd [this message]
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