OPP: Rework _set_required_devs() to manage a single device per call

JIRA: https://issues.redhat.com/browse/RHEL-81536

commit 0e8158b
Author: Ulf Hansson <ulf.hansson@linaro.org>
Date:   Wed Oct 2 14:22:24 2024 +0200

At this point there are no consumer drivers that makes use of
_set_required_devs(), hence it should be straightforward to rework the code
to enable it to better integrate with the PM domain attach procedure.

During attach, one device at the time is being hooked up to its
corresponding PM domain. Therefore, let's update the _set_required_devs()
to align to this behaviour, allowing callers to fill out one required_dev
per call. Subsequent changes starts making use of this.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20241002122232.194245-4-ulf.hansson@linaro.org
Signed-off-by: Mark Langsdorf <mlangsdo@redhat.com>

Author: mlangsdorf

drivers/opp/core.c

@@ -2509,47 +2509,73 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
 
 }
 
-static int _opp_set_required_devs(struct opp_table *opp_table,
-				  struct device *dev,
-				  struct device **required_devs)
+static int _opp_set_required_dev(struct opp_table *opp_table,
+				 struct device *dev,
+				 struct device *required_dev,
+				 unsigned int index)
 {
-	int i;
+	struct opp_table *required_table, *pd_table;
+	struct device *gdev;
 
-	if (!opp_table->required_devs) {
+	/* Genpd core takes care of propagation to parent genpd */
+	if (opp_table->is_genpd) {
+		dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
+		return -EOPNOTSUPP;
+	}
+
+	if (index >= opp_table->required_opp_count) {
 		dev_err(dev, "Required OPPs not available, can't set required devs\n");
 		return -EINVAL;
 	}
 
-	/* Another device that shares the OPP table has set the required devs ? */
-	if (opp_table->required_devs[0])
-		return 0;
+	required_table = opp_table->required_opp_tables[index];
+	if (IS_ERR(required_table)) {
+		dev_err(dev, "Missing OPP table, unable to set the required devs\n");
+		return -ENODEV;
+	}
 
-	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;
+	/*
+	 * The required_opp_tables parsing is not perfect, as the OPP core does
+	 * the parsing solely based on the DT node pointers. The core sets the
+	 * required_opp_tables entry to the first OPP table in the "opp_tables"
+	 * list, that matches with the node pointer.
+	 *
+	 * If the target DT OPP table is used by multiple devices and they all
+	 * create separate instances of 'struct opp_table' from it, then it is
+	 * possible that the required_opp_tables entry may be set to the
+	 * incorrect sibling device.
+	 *
+	 * Cross check it again and fix if required.
+	 */
+	gdev = dev_to_genpd_dev(required_dev);
+	if (IS_ERR(gdev))
+		return PTR_ERR(gdev);
+
+	pd_table = _find_opp_table(gdev);
+	if (!IS_ERR(pd_table)) {
+		if (pd_table != required_table) {
+			dev_pm_opp_put_opp_table(required_table);
+			opp_table->required_opp_tables[index] = pd_table;
+		} else {
+			dev_pm_opp_put_opp_table(pd_table);
 		}
-
-		opp_table->required_devs[i] = required_devs[i];
 	}
 
+	opp_table->required_devs[index] = required_dev;
 	return 0;
 }
 
-static void _opp_put_required_devs(struct opp_table *opp_table)
+static void _opp_put_required_dev(struct opp_table *opp_table,
+				  unsigned int index)
 {
-	int i;
-
-	for (i = 0; i < opp_table->required_opp_count; i++)
-		opp_table->required_devs[i] = NULL;
+	opp_table->required_devs[index] = NULL;
 }
 
 static void _opp_clear_config(struct opp_config_data *data)
 {
-	if (data->flags & OPP_CONFIG_REQUIRED_DEVS)
-		_opp_put_required_devs(data->opp_table);
+	if (data->flags & OPP_CONFIG_REQUIRED_DEV)
+		_opp_put_required_dev(data->opp_table,
+				      data->required_dev_index);
 	else if (data->flags & OPP_CONFIG_GENPD)
 		_opp_detach_genpd(data->opp_table);
 
@@ -2666,7 +2692,7 @@ int dev_pm_opp_set_config(struct device *dev, struct dev_pm_opp_config *config)
 
 	/* Attach genpds */
 	if (config->genpd_names) {
-		if (config->required_devs) {
+		if (config->required_dev) {
 			ret = -EINVAL;
 			goto err;
 		}
@@ -2677,13 +2703,15 @@ int dev_pm_opp_set_config(struct device *dev, struct dev_pm_opp_config *config)
 			goto err;
 
 		data->flags |= OPP_CONFIG_GENPD;
-	} else if (config->required_devs) {
-		ret = _opp_set_required_devs(opp_table, dev,
-					     config->required_devs);
+	} else if (config->required_dev) {
+		ret = _opp_set_required_dev(opp_table, dev,
+					    config->required_dev,
+					    config->required_dev_index);
 		if (ret)
 			goto err;
 
-		data->flags |= OPP_CONFIG_REQUIRED_DEVS;
+		data->required_dev_index = config->required_dev_index;
+		data->flags |= OPP_CONFIG_REQUIRED_DEV;
 	}
 
 	ret = xa_alloc(&opp_configs, &id, data, XA_LIMIT(1, INT_MAX),

drivers/opp/opp.h

@@ -35,19 +35,21 @@ extern struct list_head opp_tables;
 #define OPP_CONFIG_PROP_NAME		BIT(3)
 #define OPP_CONFIG_SUPPORTED_HW		BIT(4)
 #define OPP_CONFIG_GENPD		BIT(5)
-#define OPP_CONFIG_REQUIRED_DEVS	BIT(6)
+#define OPP_CONFIG_REQUIRED_DEV		BIT(6)
 
 /**
  * struct opp_config_data - data for set config operations
  * @opp_table: OPP table
  * @flags: OPP config flags
+ * @required_dev_index: The position in the array of required_devs
  *
  * This structure stores the OPP config information for each OPP table
  * configuration by the callers.
  */
 struct opp_config_data {
 	struct opp_table *opp_table;
 	unsigned int flags;
+	unsigned int required_dev_index;
 };
 
 /*

include/linux/pm_opp.h

@@ -74,10 +74,11 @@ typedef int (*config_clks_t)(struct device *dev, struct opp_table *opp_table,
  * @supported_hw_count: Number of elements in the array.
  * @regulator_names: Array of pointers to the names of the regulator, NULL terminated.
  * @genpd_names: Null terminated array of pointers containing names of genpd to
- *		attach. Mutually exclusive with required_devs.
+ *		attach. Mutually exclusive with required_dev.
  * @virt_devs: Pointer to return the array of genpd virtual devices. Mutually
- *		exclusive with required_devs.
- * @required_devs: Required OPP devices. Mutually exclusive with genpd_names/virt_devs.
+ *		exclusive with required_dev.
+ * @required_dev: Required OPP device. Mutually exclusive with genpd_names/virt_devs.
+ * @required_dev_index: The index of the required OPP for the @required_dev.
  *
  * This structure contains platform specific OPP configurations for the device.
  */
@@ -92,7 +93,8 @@ struct dev_pm_opp_config {
 	const char * const *regulator_names;
 	const char * const *genpd_names;
 	struct device ***virt_devs;
-	struct device **required_devs;
+	struct device *required_dev;
+	unsigned int required_dev_index;
 };
 
 #define OPP_LEVEL_UNSET			U32_MAX