firmware: arm_scmi: Add generic OPP support to the SCMI performance domain

To allow a consumer driver to use the OPP library to scale the performance
for its device, let's dynamically add the OPP table when the device gets
attached to its SCMI performance domain.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20230925131715.138411-10-ulf.hansson@linaro.orgSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/pmdomain/arm/scmi_perf_domain.c

@@ -9,6 +9,7 @@
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/pm_domain.h>
+#include <linux/pm_opp.h>
 #include <linux/scmi_protocol.h>
 #include <linux/slab.h>
 
@@ -42,6 +43,37 @@ scmi_pd_set_perf_state(struct generic_pm_domain *genpd, unsigned int state)
 	return ret;
 }
 
+static int
+scmi_pd_attach_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	struct scmi_perf_domain *pd = to_scmi_pd(genpd);
+	int ret;
+
+	/*
+	 * Allow the device to be attached, but don't add the OPP table unless
+	 * the performance level can be changed.
+	 */
+	if (!pd->info->set_perf)
+		return 0;
+
+	ret = pd->perf_ops->device_opps_add(pd->ph, dev, pd->domain_id);
+	if (ret)
+		dev_warn(dev, "failed to add OPPs for the device\n");
+
+	return ret;
+}
+
+static void
+scmi_pd_detach_dev(struct generic_pm_domain *genpd, struct device *dev)
+{
+	struct scmi_perf_domain *pd = to_scmi_pd(genpd);
+
+	if (!pd->info->set_perf)
+		return;
+
+	dev_pm_opp_remove_all_dynamic(dev);
+}
+
 static int scmi_perf_domain_probe(struct scmi_device *sdev)
 {
 	struct device *dev = &sdev->dev;
@@ -95,6 +127,8 @@ static int scmi_perf_domain_probe(struct scmi_device *sdev)
 		scmi_pd->genpd.flags = GENPD_FLAG_ALWAYS_ON |
 				       GENPD_FLAG_OPP_TABLE_FW;
 		scmi_pd->genpd.set_performance_state = scmi_pd_set_perf_state;
+		scmi_pd->genpd.attach_dev = scmi_pd_attach_dev;
+		scmi_pd->genpd.detach_dev = scmi_pd_detach_dev;
 
 		ret = pm_genpd_init(&scmi_pd->genpd, NULL, false);
 		if (ret)