Re: [PATCH] opp: Return genpd virtual devices from dev_pm_opp_attach_genpd()

From: Viresh Kumar <viresh.kumar@linaro.org>
To: Rajendra Nayak <rnayak@codeaurora.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
Subject: Re: [PATCH] opp: Return genpd virtual devices from dev_pm_opp_attach_genpd()
Date: Wed, 17 Jul 2019 11:17:13 +0530	[thread overview]
Message-ID: <20190717054713.vn65cfiqebhzdvjq@vireshk-i7> (raw)
In-Reply-To: <2ed7993d-523b-270a-2be9-83ad2426e946@codeaurora.org>

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:

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++;
        }
 

-- 
viresh
