[PATCH v7 7/8] drm/panthor: Add suspend, resume and reset handling

[Lukas Zapolskas <lukas.zapolskas@arm.com>]

The sampler must disable and re-enable counter sampling around
suspends, and must re-program the FW interface after a reset to
avoid losing data. Additionally, if a request was pending before the
reset and it was not acked, the reset will have cleared it, so we toggle
the flag and re-request a sample.

Signed-off-by: Lukas Zapolskas <lukas.zapolskas@arm.com>
---
 drivers/gpu/drm/panthor/panthor_device.c |  8 ++-
 drivers/gpu/drm/panthor/panthor_perf.c   | 83 ++++++++++++++++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_perf.h   |  6 +++
 3 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 535383ef629f..c842480472ac 100644
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -138,6 +138,7 @@ static void panthor_device_reset_work(struct work_struct *work)
 	if (!drm_dev_enter(&ptdev->base, &cookie))
 		return;
 
+	panthor_perf_pre_reset(ptdev);
 	panthor_sched_pre_reset(ptdev);
 	panthor_fw_pre_reset(ptdev, true);
 	panthor_mmu_pre_reset(ptdev);
@@ -147,6 +148,8 @@ static void panthor_device_reset_work(struct work_struct *work)
 	ret = panthor_fw_post_reset(ptdev);
 	atomic_set(&ptdev->reset.pending, 0);
 	panthor_sched_post_reset(ptdev, ret != 0);
+	if (!ret)
+		panthor_perf_post_reset(ptdev);
 	drm_dev_exit(cookie);
 
 	if (ret) {
@@ -539,8 +542,10 @@ int panthor_device_resume(struct device *dev)
 			ret = panthor_device_resume_hw_components(ptdev);
 		}
 
-		if (!ret)
+		if (!ret) {
 			panthor_sched_resume(ptdev);
+			panthor_perf_resume(ptdev);
+		}
 
 		drm_dev_exit(cookie);
 
@@ -604,6 +609,7 @@ int panthor_device_suspend(struct device *dev)
 		/* We prepare everything as if we were resetting the GPU.
 		 * The end of the reset will happen in the resume path though.
 		 */
+		panthor_perf_suspend(ptdev);
 		panthor_sched_suspend(ptdev);
 		panthor_fw_suspend(ptdev);
 		panthor_mmu_suspend(ptdev);
diff --git a/drivers/gpu/drm/panthor/panthor_perf.c b/drivers/gpu/drm/panthor/panthor_perf.c
index c66ad658a95d..28b02003f9f9 100644
--- a/drivers/gpu/drm/panthor/panthor_perf.c
+++ b/drivers/gpu/drm/panthor/panthor_perf.c
@@ -1798,6 +1798,57 @@ int panthor_perf_session_sample(struct panthor_file *pfile, u32 handle, u64 user
 	return err;
 }
 
+/**
+ * panthor_perf_suspend - Prepare the performance counter subsystem for system suspend.
+ * @ptdev: Panthor device.
+ *
+ * Indicate to the performance counters that the system is suspending.
+ *
+ * This function must not be used to handle MCU power state transitions: just before MCU goes
+ * from on to any inactive state, an automatic sample will be performed by the firmware, and
+ * the performance counter firmware state will be restored on warm boot.
+ *
+ */
+void panthor_perf_suspend(struct panthor_device *ptdev)
+{
+	struct panthor_perf *perf = ptdev->perf;
+	int ret;
+
+	if (!perf)
+		return;
+
+	guard(mutex)(&perf->op_lock);
+
+	ret = perf_disable(perf);
+
+	if (ret)
+		drm_warn(&ptdev->base, "Could not stop sampling before suspend, err = %d", ret);
+}
+
+/**
+ * panthor_perf_resume - Resume the performance counter subsystem after system resumption.
+ * @ptdev: Panthor device.
+ *
+ * Indicate to the performance counters that the system has resumed. This must not be used
+ * to handle MCU state transitions, for the same reasons as detailed in the kerneldoc for
+ * @panthor_perf_suspend.
+ */
+void panthor_perf_resume(struct panthor_device *ptdev)
+{
+	struct panthor_perf *perf = ptdev->perf;
+	int ret;
+
+	if (!perf)
+		return;
+
+	guard(mutex)(&perf->op_lock);
+
+	ret = perf_enable(perf);
+
+	if (ret)
+		drm_warn(&ptdev->base, "Could not resume sampling, err = %d", ret);
+}
+
 /**
  * panthor_perf_unplug - Terminate the performance counter subsystem.
  * @ptdev: Panthor device.
@@ -1868,3 +1919,35 @@ void panthor_perf_pool_destroy(struct panthor_file *pfile)
 
 	pfile->sessions = NULL;
 }
+
+void panthor_perf_pre_reset(struct panthor_device *ptdev)
+{
+	if (!ptdev->perf)
+		return;
+
+	guard(mutex)(&ptdev->perf->op_lock);
+
+	perf_disable(ptdev->perf);
+}
+
+void panthor_perf_post_reset(struct panthor_device *ptdev)
+{
+	bool rerequest = false;
+
+	if (!ptdev->perf)
+		return;
+
+	guard(mutex)(&ptdev->perf->op_lock);
+
+	perf_enable(ptdev->perf);
+
+	scoped_guard(spinlock_irqsave, &ptdev->perf->pend_lock) {
+		rerequest = ptdev->perf->fw_sample_requested;
+
+		if (rerequest)
+			ptdev->perf->fw_sample_requested = false;
+	}
+
+	if (rerequest)
+		perf_fw_request_sample(ptdev->perf);
+}
diff --git a/drivers/gpu/drm/panthor/panthor_perf.h b/drivers/gpu/drm/panthor/panthor_perf.h
index 0e1172dbae39..e4a323fe6f0d 100644
--- a/drivers/gpu/drm/panthor/panthor_perf.h
+++ b/drivers/gpu/drm/panthor/panthor_perf.h
@@ -18,6 +18,8 @@ int panthor_perf_pool_create(struct panthor_file *pfile);
 void panthor_perf_pool_destroy(struct panthor_file *pfile);
 
 int panthor_perf_init(struct panthor_device *ptdev);
+void panthor_perf_suspend(struct panthor_device *ptdev);
+void panthor_perf_resume(struct panthor_device *ptdev);
 void panthor_perf_unplug(struct panthor_device *ptdev);
 
 int panthor_perf_session_create(struct drm_file *file,
@@ -30,5 +32,9 @@ int panthor_perf_session_sample(struct panthor_file *pfile, unsigned int handle,
 
 void panthor_perf_report_irq(struct panthor_device *ptdev, u32 status);
 
+void panthor_perf_pre_reset(struct panthor_device *ptdev);
+
+void panthor_perf_post_reset(struct panthor_device *ptdev);
+
 #endif /* __PANTHOR_PERF_H__ */
 

-- 
2.43.0