linux-kernel - [PATCH v2 5/8] drm/panthor: Implement soft reset via PWR

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Message-ID: <20251024202117.3241292-6-karunika.choo@arm.com>
Date: Fri, 24 Oct 2025 21:21:14 +0100
From: Karunika Choo <karunika.choo@....com>
To: dri-devel@...ts.freedesktop.org
Cc: nd@....com,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Steven Price <steven.price@....com>,
	Liviu Dudau <liviu.dudau@....com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/8] 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.

Signed-off-by: Karunika Choo <karunika.choo@....com>
---
v2:
 * Dropped RESET_FAST implementation as it is not currently being used.
 * Renamed reset_completed to reset_pending to align with underlying
   logic and fixed the logic of its callers accordingly.
 * Improved readability of panthor_pwr_reset() and removed inline
   ternary expressions.
---
 drivers/gpu/drm/panthor/panthor_pwr.c | 50 +++++++++++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_pwr.h |  2 ++
 2 files changed, 52 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_pwr.c b/drivers/gpu/drm/panthor/panthor_pwr.c
index cd529660a276..4edb818c7ac4 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>

@@ -31,6 +32,8 @@

 #define PWR_RETRACT_TIMEOUT_US		(2ULL * USEC_PER_MSEC)

+#define PWR_RESET_TIMEOUT_MS		500
+
 /**
  * struct panthor_pwr - PWR_CONTROL block management data.
  */
@@ -75,6 +78,43 @@ 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) {
@@ -428,6 +468,16 @@ 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);
--
2.49.0