drm/panthor: Implement soft reset via PWR_CONTROL

Add helpers to issue reset commands through the PWR_CONTROL interface
and wait for reset completion using IRQ signaling. This enables support
for RESET_SOFT operations with timeout handling and status verification.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Karunika Choo <karunika.choo@arm.com>
Link: https://patch.msgid.link/20251125125548.3282320-6-karunika.choo@arm.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

2 files changed, 52 insertions, 0 deletions

diff --git a/drivers/gpu/drm/panthor/panthor_pwr.c b/drivers/gpu/drm/panthor/panthor_pwr.c
index 6dff5daf77d2..57cfc7ce715b 100644
--- a/drivers/gpu/drm/panthor/panthor_pwr.c
+++ b/drivers/gpu/drm/panthor/panthor_pwr.c
@@ -3,6 +3,7 @@
 
 #include <linux/platform_device.h>
 #include <linux/interrupt.h>
+#include <linux/cleanup.h>
 #include <linux/iopoll.h>
 #include <linux/wait.h>
 
@@ -32,6 +33,8 @@
 
 #define PWR_RETRACT_TIMEOUT_US		(2ULL * USEC_PER_MSEC)
 
+#define PWR_RESET_TIMEOUT_MS		500
+
 /**
  * struct panthor_pwr - PWR_CONTROL block management data.
  */
@@ -76,6 +79,43 @@ static void panthor_pwr_write_command(struct panthor_device *ptdev, u32 command,
 	gpu_write(ptdev, PWR_COMMAND, command);
 }
 
+static bool reset_irq_raised(struct panthor_device *ptdev)
+{
+	return gpu_read(ptdev, PWR_INT_RAWSTAT) & PWR_IRQ_RESET_COMPLETED;
+}
+
+static bool reset_pending(struct panthor_device *ptdev)
+{
+	return (ptdev->pwr->pending_reqs & PWR_IRQ_RESET_COMPLETED);
+}
+
+static int panthor_pwr_reset(struct panthor_device *ptdev, u32 reset_cmd)
+{
+	scoped_guard(spinlock_irqsave, &ptdev->pwr->reqs_lock) {
+		if (reset_pending(ptdev)) {
+			drm_WARN(&ptdev->base, 1, "Reset already pending");
+		} else {
+			ptdev->pwr->pending_reqs |= PWR_IRQ_RESET_COMPLETED;
+			gpu_write(ptdev, PWR_INT_CLEAR, PWR_IRQ_RESET_COMPLETED);
+			panthor_pwr_write_command(ptdev, reset_cmd, 0);
+		}
+	}
+
+	if (!wait_event_timeout(ptdev->pwr->reqs_acked, !reset_pending(ptdev),
+				msecs_to_jiffies(PWR_RESET_TIMEOUT_MS))) {
+		guard(spinlock_irqsave)(&ptdev->pwr->reqs_lock);
+
+		if (reset_pending(ptdev) && !reset_irq_raised(ptdev)) {
+			drm_err(&ptdev->base, "RESET timed out (0x%x)", reset_cmd);
+			return -ETIMEDOUT;
+		}
+
+		ptdev->pwr->pending_reqs &= ~PWR_IRQ_RESET_COMPLETED;
+	}
+
+	return 0;
+}
+
 static const char *get_domain_name(u8 domain)
 {
 	switch (domain) {
@@ -429,6 +469,16 @@ int panthor_pwr_init(struct panthor_device *ptdev)
 	return 0;
 }
 
+int panthor_pwr_reset_soft(struct panthor_device *ptdev)
+{
+	if (!(gpu_read64(ptdev, PWR_STATUS) & PWR_STATUS_ALLOW_SOFT_RESET)) {
+		drm_err(&ptdev->base, "RESET_SOFT not allowed");
+		return -EOPNOTSUPP;
+	}
+
+	return panthor_pwr_reset(ptdev, PWR_COMMAND_RESET_SOFT);
+}
+
 void panthor_pwr_l2_power_off(struct panthor_device *ptdev)
 {
 	const u64 l2_allow_mask = PWR_STATUS_DOMAIN_ALLOWED(PWR_COMMAND_DOMAIN_L2);
diff --git a/drivers/gpu/drm/panthor/panthor_pwr.h b/drivers/gpu/drm/panthor/panthor_pwr.h
index 3c834059a860..adf1f6136abc 100644
--- a/drivers/gpu/drm/panthor/panthor_pwr.h
+++ b/drivers/gpu/drm/panthor/panthor_pwr.h
@@ -10,6 +10,8 @@ void panthor_pwr_unplug(struct panthor_device *ptdev);
 
 int panthor_pwr_init(struct panthor_device *ptdev);
 
+int panthor_pwr_reset_soft(struct panthor_device *ptdev);
+
 void panthor_pwr_l2_power_off(struct panthor_device *ptdev);
 
 int panthor_pwr_l2_power_on(struct panthor_device *ptdev);