Re: [PATCH 3/7] OPP: Rework _set_required_devs() to manage a single device per call

On Wed, 26 Jun 2024 at 08:33, Viresh Kumar [off-list ref] wrote:

On 19-06-24, 16:08, Ulf Hansson wrote:

quoted

@@ -2494,36 +2495,68 @@ static int _opp_set_required_devs(struct opp_table *opp_table,
              return -EINVAL;
      }

-     /* Another device that shares the OPP table has set the required devs ? */
-     if (opp_table->required_devs[0])
-             return 0;
+     /* Genpd core takes care of propagation to parent genpd */
+     if (opp_table->is_genpd) {

A genpd can have non-genpd devices in the required OPPs and so this
isn't sufficient. What we were ignoring earlier was genpd having
another genpd as required opp.

Unless I am mistaken, I don't think that is a scenario we should care
about here.

_opp_set_required_dev() is being called for a device that is about to
be attached to its corresponding genpd.

Yes, in some cases, we attach a genpd provider's device to its
genpd-parent, but that is not to control the required-opps.

quoted

+             dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
+             return -EOPNOTSUPP;
+     }

      for (i = 0; i < opp_table->required_opp_count; i++) {
-             /* Genpd core takes care of propagation to parent genpd */
-             if (required_devs[i] && opp_table->is_genpd &&
-                 opp_table->required_opp_tables[i]->is_genpd) {
-                     dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
-                     return -EOPNOTSUPP;
-             }
+             struct opp_table *table = opp_table->required_opp_tables[i];
+
+             /*
+              * The OPP table should be available at this point. If not, it's
+              * not the one we are looking for.
+              */
+             if (IS_ERR(table))
+                     continue;
+
+             /* Move to the next available index. */
+             if (opp_table->required_devs[i])
+                     continue;

-             opp_table->required_devs[i] = required_devs[i];
+             /*
+              * We need to compare the nodes for the OPP tables, rather than
+              * the OPP tables themselves, as we may have separate instances.
+              */
+             if (required_opp_table->np == table->np) {
+

We don't keep such empty lines in OPP core generally at this place.

Yep, let me drop it!

quoted

+                     /* Cross check the OPP tables and fix it if needed. */

Copy the bigger comment from_opp_attach_genpd() here too. It helps
understanding why required_opp_tables entry is getting replaced.

Right, makes sense!

quoted

+                     if (required_opp_table != table) {
+                             dev_pm_opp_put_opp_table(table);
+                             _get_opp_table_kref(required_opp_table);
+                             opp_table->required_opp_tables[i] = required_opp_table;
+                     }
+
+                     opp_table->required_devs[i] = required_dev;
+
+                     /*
+                      * Add the required_dev as a user of the OPP table, so
+                      * we can call dev_pm_opp_set_opp() on it directly.
+                      */
+                     if (!_add_opp_dev(required_dev, required_opp_table)) {
+                             dev_err(dev, "Failed to add the device to the required OPP table\n");
+                             return -ENOMEM;
+                     }
+
+                     return i;
+             }
      }

--
viresh

Kind regards
Uffe