[PATCH v8 4/5] drm/panthor: Use existing OPP table if present

Nicolas Frattaroli
2025-10-17T15:32:21Z

On SoCs where the GPU's power-domain is in charge of setting performance
levels, the OPP table of the GPU node will have already been populated
during said power-domain's attach_dev operation.

To avoid initialising an OPP table twice, only set the OPP regulator and
the OPPs from DT if there's no OPP table present.

Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
---
drivers/gpu/drm/panthor/panthor_devfreq.c | 32 ++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.c b/drivers/gpu/drm/panthor/panthor_devfreq.c
index a6dca599f0a5..ec63e27f4883 100644
--- a/drivers/gpu/drm/panthor/panthor_devfreq.c
+++ b/drivers/gpu/drm/panthor/panthor_devfreq.c
@@ -141,6 +141,7 @@ int panthor_devfreq_init(struct panthor_device *ptdev)
struct thermal_cooling_device *cooling;
struct device *dev = ptdev->base.dev;
struct panthor_devfreq *pdevfreq;
+ struct opp_table *table;
struct dev_pm_opp *opp;
unsigned long cur_freq;
unsigned long freq = ULONG_MAX;
@@ -152,17 +153,30 @@ int panthor_devfreq_init(struct panthor_device *ptdev)

ptdev->devfreq = pdevfreq;

- ret = devm_pm_opp_set_regulators(dev, reg_names);
- if (ret && ret != -ENODEV) {
- if (ret != -EPROBE_DEFER)
- DRM_DEV_ERROR(dev, "Couldn't set OPP regulators\n");
- return ret;
+ /*
+ * The power domain associated with the GPU may have already added an
+ * OPP table, complete with OPPs, as part of the platform bus
+ * initialization. If this is the case, the power domain is in charge of
+ * also controlling the performance, with a set_performance callback.
+ * Only add a new OPP table from DT if there isn't such a table present
+ * already.
+ */
+ table = dev_pm_opp_get_opp_table(dev);
+ if (IS_ERR_OR_NULL(table)) {
+ ret = devm_pm_opp_set_regulators(dev, reg_names);
+ if (ret && ret != -ENODEV) {
+ if (ret != -EPROBE_DEFER)
+ DRM_DEV_ERROR(dev, "Couldn't set OPP regulators\n");
+ return ret;
+ }
+
+ ret = devm_pm_opp_of_add_table(dev);
+ if (ret)
+ return ret;
+ } else {
+ dev_pm_opp_put_opp_table(table);
}

- ret = devm_pm_opp_of_add_table(dev);
- if (ret)
- return ret;
-
spin_lock_init(&pdevfreq->lock);

panthor_devfreq_reset(pdevfreq);

--
2.51.0