linux-kernel - Re: [RESEND PATCH 2/2] soc: qcom: rpmhpd: Make power

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Date:   Thu, 15 Jul 2021 17:54:21 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Sibi Sankar <sibis@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH 2/2] soc: qcom: rpmhpd: Make power_on actually
 enable the domain


On 7/15/2021 5:46 PM, Sibi Sankar wrote:
> Hey Bjorn,
> 
> Thanks for the patch.
> 
> On 2021-07-03 08:24, Bjorn Andersson wrote:
>> The general expectation is that powering on a power-domain should make
>> the power domain deliver some power, and if a specific performace state
> 
> s/performace/performance/
> 
>> is needed further requests has to be made.
>>
>> But in contrast with other power-domain implementations (e.g. rpmpd) the
>> RPMh does not have an interface to enable the power, so the driver has
>> to vote for a particular corner (performance level) in rpmh_power_on().
>>
>> But the corner is never initialized, so a typical request to simply
>> enable the power domain would not actually turn on the hardware. Further
>> more, when no more clients vote for a performance state (i.e. the
>> aggregated vote is 0) the power domain would be turn off.
>>
>> Fix both of these issues by always voting for a corner with non-zero
>> value, when the power domain is enabled.
>>
>> The tracking of the lowest non-zero corner is performed to handle the
>> corner case if there's ever a domain with a non-zero lowest corner, in
>> which case both rpmh_power_on() and rpmh_rpmhpd_set_performance_state()
>> would be allowed to use this lowest corner.
>>
>> Fixes: 279b7e8a62cc ("soc: qcom: rpmhpd: Add RPMh power domain driver")
>> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>> ---
>>
>> Resending because the hunk in rpmhpd_update_level_mapping() was left in the
>> index.
>>
>>  drivers/soc/qcom/rpmhpd.c | 18 ++++++++++++++----
>>  1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/soc/qcom/rpmhpd.c b/drivers/soc/qcom/rpmhpd.c
>> index fa209b479ab3..76ea6b053ef0 100644
>> --- a/drivers/soc/qcom/rpmhpd.c
>> +++ b/drivers/soc/qcom/rpmhpd.c
>> @@ -30,6 +30,7 @@
>>   * @active_only:    True if it represents an Active only peer
>>   * @corner:        current corner
>>   * @active_corner:    current active corner
>> + * @enable_corner:    lowest non-zero corner
>>   * @level:        An array of level (vlvl) to corner (hlvl) mappings
>>   *            derived from cmd-db
>>   * @level_count:    Number of levels supported by the power domain. max
>> @@ -47,6 +48,7 @@ struct rpmhpd {
>>      const bool    active_only;
>>      unsigned int    corner;
>>      unsigned int    active_corner;
>> +    unsigned int    enable_corner;
>>      u32        level[RPMH_ARC_MAX_LEVELS];
>>      size_t        level_count;
>>      bool        enabled;
>> @@ -385,13 +387,13 @@ static int rpmhpd_aggregate_corner(struct rpmhpd
>> *pd, unsigned int corner)
>>  static int rpmhpd_power_on(struct generic_pm_domain *domain)
>>  {
>>      struct rpmhpd *pd = domain_to_rpmhpd(domain);
>> -    int ret = 0;
>> +    unsigned int corner;
>> +    int ret;
>>
>>      mutex_lock(&rpmhpd_lock);
>>
>> -    if (pd->corner)
>> -        ret = rpmhpd_aggregate_corner(pd, pd->corner);
>> -
>> +    corner = max(pd->corner, pd->enable_corner);
>> +    ret = rpmhpd_aggregate_corner(pd, corner);
>>      if (!ret)
>>          pd->enabled = true;
>>
>> @@ -436,6 +438,10 @@ static int rpmhpd_set_performance_state(struct
>> generic_pm_domain *domain,
>>          i--;
>>
>>      if (pd->enabled) {
>> +        /* Ensure that the domain isn't turn off */
>> +        if (i < pd->enable_corner)
>> +            i = pd->enable_corner;
>> +
>>          ret = rpmhpd_aggregate_corner(pd, i);
>>          if (ret)
>>              goto out;
>> @@ -472,6 +478,10 @@ static int rpmhpd_update_level_mapping(struct
>> rpmhpd *rpmhpd)
>>      for (i = 0; i < rpmhpd->level_count; i++) {
>>          rpmhpd->level[i] = buf[i];
>>
>> +        /* Remember the first non-zero corner */
> 
> Shouldn't we be tracking the corner that
> corresponds to the first non-zero level
> instead?

Thats correct, thanks for spotting this, the first non-zero
corner is always 1 :)

> 
>> +        if (!rpmhpd->enable_corner)
>> +            rpmhpd->enable_corner = i;
>> +
>>          /*
>>           * The AUX data may be zero padded.  These 0 valued entries at
>>           * the end of the map must be ignored.
> 

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