[PATCH 2/2] drm/imagination: Disable interrupts before suspending the GPU

[Alessio Belle <alessio.belle@imgtec.com>]

This is an additional safety layer to ensure no accesses to the GPU
registers can be made while it is powered off.

While we can disable IRQ generation from GPU, META firmware, MIPS
firmware and for safety events, we cannot do the same for the RISC-V
firmware.
To keep a unified approach, once the firmware has completed its power
off sequence, disable IRQs for the while GPU at the kernel level
instead.

Signed-off-by: Alessio Belle <alessio.belle@imgtec.com>
---
 drivers/gpu/drm/imagination/pvr_power.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_power.c b/drivers/gpu/drm/imagination/pvr_power.c
index f50cdea30680..3f22b07e3301 100644
--- a/drivers/gpu/drm/imagination/pvr_power.c
+++ b/drivers/gpu/drm/imagination/pvr_power.c
@@ -92,9 +92,9 @@ pvr_power_request_pwr_off(struct pvr_device *pvr_dev)
 static int
 pvr_power_fw_disable(struct pvr_device *pvr_dev, bool hard_reset, bool rpm_suspend)
 {
-	if (!hard_reset) {
-		int err;
+	int err;
 
+	if (!hard_reset) {
 		cancel_delayed_work_sync(&pvr_dev->watchdog.work);
 
 		err = pvr_power_request_idle(pvr_dev);
@@ -107,33 +107,46 @@ pvr_power_fw_disable(struct pvr_device *pvr_dev, bool hard_reset, bool rpm_suspe
 	}
 
 	if (rpm_suspend) {
-		/* Wait for late processing of GPU or firmware IRQs in other cores */
-		synchronize_irq(pvr_dev->irq);
+		/* This also waits for late processing of GPU or firmware IRQs in other cores */
+		disable_irq(pvr_dev->irq);
 	}
 
-	return pvr_fw_stop(pvr_dev);
+	err = pvr_fw_stop(pvr_dev);
+	if (err && rpm_suspend)
+		enable_irq(pvr_dev->irq);
+
+	return err;
 }
 
 static int
-pvr_power_fw_enable(struct pvr_device *pvr_dev)
+pvr_power_fw_enable(struct pvr_device *pvr_dev, bool rpm_resume)
 {
 	int err;
 
+	if (rpm_resume)
+		enable_irq(pvr_dev->irq);
+
 	err = pvr_fw_start(pvr_dev);
 	if (err)
-		return err;
+		goto out;
 
 	err = pvr_wait_for_fw_boot(pvr_dev);
 	if (err) {
 		drm_err(from_pvr_device(pvr_dev), "Firmware failed to boot\n");
 		pvr_fw_stop(pvr_dev);
-		return err;
+		goto out;
 	}
 
 	queue_delayed_work(pvr_dev->sched_wq, &pvr_dev->watchdog.work,
 			   msecs_to_jiffies(WATCHDOG_TIME_MS));
 
 	return 0;
+
+out:
+	if (rpm_resume)
+		disable_irq(pvr_dev->irq);
+
+	return err;
 }
 
 bool
@@ -396,7 +409,7 @@ pvr_power_device_resume(struct device *dev)
 		goto err_drm_dev_exit;
 
 	if (pvr_dev->fw_dev.booted) {
-		err = pvr_power_fw_enable(pvr_dev);
+		err = pvr_power_fw_enable(pvr_dev, true);
 		if (err)
 			goto err_power_off;
 	}
@@ -546,7 +559,7 @@ pvr_power_reset(struct pvr_device *pvr_dev, bool hard_reset)
 
 			pvr_fw_irq_clear(pvr_dev);
 
-			err = pvr_power_fw_enable(pvr_dev);
+			err = pvr_power_fw_enable(pvr_dev, false);
 		}
 
 		if (err && hard_reset)

-- 
2.43.0