Re: [PATCH v3 5/7] drivers: firmware: psci: Add hierarchical domain idle states converter

Maulik Shah
2020-02-05T12:23:12Z

On 2/4/2020 8:51 PM, Sudeep Holla wrote:
> On Tue, Feb 04, 2020 at 10:22:42AM +0530, Maulik Shah wrote:
>> On 2/3/2020 10:38 PM, Sudeep Holla wrote:
>>> On Mon, Feb 03, 2020 at 07:05:38PM +0530, Maulik Shah wrote:
>>>> From: Ulf Hansson <ulf.hansson@linaro.org>
>>>>
>>>> If the hierarchical CPU topology is used, but the OS initiated mode isn't
>>>> supported, we need to rely solely on the regular cpuidle framework to
>>>> manage the idle state selection, rather than using genpd and its
>>>> governor.
>>>>
>>>> For this reason, introduce a new PSCI DT helper function,
>>>> psci_dt_pm_domains_parse_states(), which parses and converts the
>>>> hierarchically described domain idle states from DT, into regular flattened
>>>> cpuidle states. The converted states are added to the existing cpuidle
>>>> driver's array of idle states, which make them available for cpuidle.
>>>>
>>> And what's the main motivation for this if OSI is not supported in the
>>> firmware ?
>> Hi Sudeep,
>>
>> Main motivation is to do last-man activities before the CPU cluster can
>> enter a deep idle state.
>>
> Details on those last-man activities will help the discussion. Basically
> I am wondering what they are and why they need to done in OSPM ?

Hi Sudeep,

there are cases like,

Last cpu going to deepest idle mode need to lower various resoruce
requirements (for eg DDR freq).

This is done by calling rpmh_flush which send SLEEP values for various
shared resources.

>>>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>>>> [applied to new path, resolved conflicts]
>>>> Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
>>>> ---
>>>> drivers/cpuidle/cpuidle-psci-domain.c | 137 +++++++++++++++++++++++++++++-----
>>>> drivers/cpuidle/cpuidle-psci.c | 41 +++++-----
>>>> drivers/cpuidle/cpuidle-psci.h | 11 +++
>>>> 3 files changed, 153 insertions(+), 36 deletions(-)
>>>>
>>>> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
>>>> index 423f03b..3c417f7 100644
>>>> --- a/drivers/cpuidle/cpuidle-psci-domain.c
>>>> +++ b/drivers/cpuidle/cpuidle-psci-domain.c
>>>> @@ -26,13 +26,17 @@ struct psci_pd_provider {
>>>> };
>>>>
>>>> static LIST_HEAD(psci_pd_providers);
>>>> -static bool osi_mode_enabled __initdata;
>>>> +static bool osi_mode_enabled;
>>>>
>>>> static int psci_pd_power_off(struct generic_pm_domain *pd)
>>>> {
>>>> struct genpd_power_state *state = &pd->states[pd->state_idx];
>>>> u32 *pd_state;
>>>>
>>>> + /* If we have failed to enable OSI mode, then abort power off. */
>>>> + if ((psci_has_osi_support()) && !osi_mode_enabled)
>>>> + return -EBUSY;
>>>> +
>>> Why is this needed ? IIUC we don't create genpd domains if OSI is not
>>> enabled.
>> we do create genpd domains, for cpu domains, we just abort power off here
>> since idle states are converted into regular flattened mode.
>>
> OK, IIRC the OSI patches from Ulf didn't add the genpd or rather removed
> them in case of any failure to enable OSI. Has that been changed ? If so,
> why ?
>
>> however genpd poweroff will be used by parent domain (rsc in this case)
>> which is kept in hireachy in DTSI with cluster domain to do last man
>> activities.
>>
> I am bit confused here. Either we do OSI or PC and what you are describing
> sounds like a mix-n-match to me and I am totally against it.

we still do PC based on sc7180. there is no OSI.

can you please check v4 series, i have cleaned this change by remove
converter part.

Thanks,

Maulik

>
> --
> Regards,
> Sudeep

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