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Subject: Re: [PATCH] opp: Return genpd virtual devices from
 dev_pm_opp_attach_genpd()
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>, linux-pm@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        linux-kernel@vger.kernel.org
References: <027985ce35873cd218298302a1408da06d48458b.1562565567.git.viresh.kumar@linaro.org>
 <2ed7993d-523b-270a-2be9-83ad2426e946@codeaurora.org>
 <20190717054713.vn65cfiqebhzdvjq@vireshk-i7>
From:   Rajendra Nayak <rnayak@codeaurora.org>
Message-ID: <2fbfc0fc-7d61-bf8c-67de-28183d03e26a@codeaurora.org>
Date:   Wed, 17 Jul 2019 15:34:38 +0530
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On 7/17/2019 11:17 AM, Viresh Kumar wrote:
> On 11-07-19, 15:09, Rajendra Nayak wrote:
>> Sorry for the delay
> 
> Same here :)
> 
>> I seem to have completely missed this patch.
>> I just gave this a try and here are some observations,
>>
>> I have a case where I have one device with 2 power domains, one of them
>> is scale-able (supports perf state) and the other one supports only being
>> turned on and off.
>>
>> 1. In the driver I now need to use dev_pm_domain_attach_by_name/id to attach the
>> power domain which supports only on/off and then use dev_pm_opp_attach_genpd()
>> for the one which supports perf states.
>>
>> 2. My OPP table has only 1 required_opps, so the required_opp_count for the OPP table is 1.
>> Now if my device tree has my scale-able powerdomain at index 1 (it works if its at index 0)
>> then I end up with this error
>>
>> [    2.858628] ufshcd-qcom 1d84000.ufshc: Index can't be greater than required-opp-count - 1, rpmh_pd (1 : 1)
>>
>> so it looks like a lot of the OPP core today just assumes that if a device has multiple power domains,
>> all of them are scale-able which isn't necessarily true.
> 
> I don't think a lot of OPP core has these problems, but maybe only
> this place. I was taking care of this since the beginning just forgot
> it now.
> 
> What about this over this commit:

Yes, this does seem to fix my concern mentioned in 2. above.

> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index d76ead4eff4c..1f11f8c92337 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1789,13 +1789,16 @@ static void _opp_detach_genpd(struct opp_table *opp_table)
>    *
>    * This helper needs to be called once with a list of all genpd to attach.
>    * Otherwise the original device structure will be used instead by the OPP core.
> + *
> + * The order of entries in the names array must match the order in which
> + * "required-opps" are added in DT.
>    */
>   struct opp_table *dev_pm_opp_attach_genpd(struct device *dev,
>                  const char **names, struct device ***virt_devs)
>   {
>          struct opp_table *opp_table;
>          struct device *virt_dev;
> -       int index, ret = -EINVAL;
> +       int index = 0, ret = -EINVAL;
>          const char **name = names;
>   
>          opp_table = dev_pm_opp_get_opp_table(dev);
> @@ -1821,14 +1824,6 @@ struct opp_table *dev_pm_opp_attach_genpd(struct device *dev,
>                  goto unlock;
>   
>          while (*name) {
> -               index = of_property_match_string(dev->of_node,
> -                                                "power-domain-names", *name);
> -               if (index < 0) {
> -                       dev_err(dev, "Failed to find power domain: %s (%d)\n",
> -                               *name, index);
> -                       goto err;
> -               }
> -
>                  if (index >= opp_table->required_opp_count) {
>                          dev_err(dev, "Index can't be greater than required-opp-count - 1, %s (%d : %d)\n",
>                                  *name, opp_table->required_opp_count, index);
> @@ -1849,6 +1844,7 @@ struct opp_table *dev_pm_opp_attach_genpd(struct device *dev,
>                  }
>   
>                  opp_table->genpd_virt_devs[index] = virt_dev;
> +               index++;
>                  name++;
>          }
>   
> 

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