Message-ID: <20251024202117.3241292-5-karunika.choo@arm.com>
Date: Fri, 24 Oct 2025 21:21:13 +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 4/8] drm/panthor: Implement L2 power on/off via PWR_CONTROL

This patch adds common helpers to issue power commands, poll
transitions, and validate domain state, then wires them into the L2
on/off paths.

The L2 power-on sequence now delegates control of the SHADER and TILER
domains to the MCU when allowed, while the L2 itself is never delegated.
On power-off, dependent domains beneath the L2 are checked, and if
necessary, retracted and powered down to maintain proper domain
ordering.

Signed-off-by: Karunika Choo <karunika.choo@....com>
---
v2:
 * Updated GENMASK to GENMASK_U64 to address kernel test robot warnings
   for 32-bit systems.
 * Removed panthor_pwr_read_status() in favour of a simple gpu_read64()
   operation on the PWR_STATUS register.
 * Renamed panthor_pwr_info_show() to panthor_pwr_debug_info_show() for
   more clarity.
 * Added additional WARN_ON for an invalid domain when requesting power
   domain transition.
 * Made panthor_pwr_domain_transition()'s expected val logic more
   readable and clearer.
 * Wait on domain power transition instead of failing the operation.
 * Fixed inconsistent error return value vs kerneldoc.
 * Removed confusing drm_dbg in delegate_domain() in favor of a comment.
 * Add unwind to panthor_pwr_delegate_domains().
 * Moved child domain handling logic from panthor_pwr_l2_power_off()
   into panthor_pwr_domain_force_off().
 * Added additional clarification regarding delegation and retraction of
   power domains.
 * Minor formatting and readability changes and remove unnecessary
   checks.
---
 drivers/gpu/drm/panthor/panthor_pwr.c  | 378 +++++++++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_pwr.h  |   4 +
 drivers/gpu/drm/panthor/panthor_regs.h |   1 +
 3 files changed, 383 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_pwr.c b/drivers/gpu/drm/panthor/panthor_pwr.c
index da64fe006a8b..cd529660a276 100644
--- a/drivers/gpu/drm/panthor/panthor_pwr.c
+++ b/drivers/gpu/drm/panthor/panthor_pwr.c
@@ -23,6 +23,14 @@
 	 PWR_IRQ_COMMAND_NOT_ALLOWED | \
 	 PWR_IRQ_COMMAND_INVALID)

+#define PWR_ALL_CORES_MASK		GENMASK_U64(63, 0)
+
+#define PWR_DOMAIN_MAX_BITS		16
+
+#define PWR_TRANSITION_TIMEOUT_US	(2ULL * USEC_PER_SEC)
+
+#define PWR_RETRACT_TIMEOUT_US		(2ULL * USEC_PER_MSEC)
+
 /**
  * struct panthor_pwr - PWR_CONTROL block management data.
  */
@@ -59,6 +67,323 @@ static void panthor_pwr_irq_handler(struct panthor_device *ptdev, u32 status)
 }
 PANTHOR_IRQ_HANDLER(pwr, PWR, panthor_pwr_irq_handler);

+static void panthor_pwr_write_command(struct panthor_device *ptdev, u32 command, u64 args)
+{
+	if (args)
+		gpu_write64(ptdev, PWR_CMDARG, args);
+
+	gpu_write(ptdev, PWR_COMMAND, command);
+}
+
+static const char *get_domain_name(u8 domain)
+{
+	switch (domain) {
+	case PWR_COMMAND_DOMAIN_L2:
+		return "L2";
+	case PWR_COMMAND_DOMAIN_TILER:
+		return "Tiler";
+	case PWR_COMMAND_DOMAIN_SHADER:
+		return "Shader";
+	case PWR_COMMAND_DOMAIN_BASE:
+		return "Base";
+	case PWR_COMMAND_DOMAIN_STACK:
+		return "Stack";
+	}
+	return "Unknown";
+}
+
+static u32 get_domain_base(u8 domain)
+{
+	switch (domain) {
+	case PWR_COMMAND_DOMAIN_L2:
+		return PWR_L2_PRESENT;
+	case PWR_COMMAND_DOMAIN_TILER:
+		return PWR_TILER_PRESENT;
+	case PWR_COMMAND_DOMAIN_SHADER:
+		return PWR_SHADER_PRESENT;
+	case PWR_COMMAND_DOMAIN_BASE:
+		return PWR_BASE_PRESENT;
+	case PWR_COMMAND_DOMAIN_STACK:
+		return PWR_STACK_PRESENT;
+	}
+	return 0;
+}
+
+static u32 get_domain_ready_reg(u32 domain)
+{
+	return get_domain_base(domain) + (PWR_L2_READY - PWR_L2_PRESENT);
+}
+
+static u32 get_domain_pwrtrans_reg(u32 domain)
+{
+	return get_domain_base(domain) + (PWR_L2_PWRTRANS - PWR_L2_PRESENT);
+}
+
+static bool is_valid_domain(u32 domain)
+{
+	return get_domain_base(domain) != 0;
+}
+
+static bool has_rtu(struct panthor_device *ptdev)
+{
+	return ptdev->gpu_info.gpu_features & GPU_FEATURES_RAY_TRAVERSAL;
+}
+
+static u8 get_domain_subdomain(struct panthor_device *ptdev, u32 domain)
+{
+	if ((domain == PWR_COMMAND_DOMAIN_SHADER) && has_rtu(ptdev))
+		return PWR_COMMAND_SUBDOMAIN_RTU;
+
+	return 0;
+}
+
+static int panthor_pwr_domain_wait_transition(struct panthor_device *ptdev, u32 domain,
+					      u32 timeout_us)
+{
+	u32 pwrtrans_reg = get_domain_pwrtrans_reg(domain);
+	u64 val;
+	int ret = 0;
+
+	ret = gpu_read64_poll_timeout(ptdev, pwrtrans_reg, val, !(PWR_ALL_CORES_MASK & val), 100,
+				      timeout_us);
+	if (ret) {
+		drm_err(&ptdev->base, "%s domain power in transition, pwrtrans(0x%llx)",
+			get_domain_name(domain), val);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void panthor_pwr_debug_info_show(struct panthor_device *ptdev)
+{
+	drm_info(&ptdev->base, "GPU_FEATURES:    0x%016llx", gpu_read64(ptdev, GPU_FEATURES));
+	drm_info(&ptdev->base, "PWR_STATUS:      0x%016llx", gpu_read64(ptdev, PWR_STATUS));
+	drm_info(&ptdev->base, "L2_PRESENT:      0x%016llx", gpu_read64(ptdev, PWR_L2_PRESENT));
+	drm_info(&ptdev->base, "L2_PWRTRANS:     0x%016llx", gpu_read64(ptdev, PWR_L2_PWRTRANS));
+	drm_info(&ptdev->base, "L2_READY:        0x%016llx", gpu_read64(ptdev, PWR_L2_READY));
+	drm_info(&ptdev->base, "TILER_PRESENT:   0x%016llx", gpu_read64(ptdev, PWR_TILER_PRESENT));
+	drm_info(&ptdev->base, "TILER_PWRTRANS:  0x%016llx", gpu_read64(ptdev, PWR_TILER_PWRTRANS));
+	drm_info(&ptdev->base, "TILER_READY:     0x%016llx", gpu_read64(ptdev, PWR_TILER_READY));
+	drm_info(&ptdev->base, "SHADER_PRESENT:  0x%016llx", gpu_read64(ptdev, PWR_SHADER_PRESENT));
+	drm_info(&ptdev->base, "SHADER_PWRTRANS: 0x%016llx", gpu_read64(ptdev, PWR_SHADER_PWRTRANS));
+	drm_info(&ptdev->base, "SHADER_READY:    0x%016llx", gpu_read64(ptdev, PWR_SHADER_READY));
+}
+
+static int panthor_pwr_domain_transition(struct panthor_device *ptdev, u32 cmd, u32 domain,
+					 u64 mask, u32 timeout_us)
+{
+	u32 ready_reg = get_domain_ready_reg(domain);
+	u32 pwr_cmd = PWR_COMMAND_DEF(cmd, domain, get_domain_subdomain(ptdev, domain));
+	u64 expected_val = 0;
+	u64 val;
+	int ret = 0;
+
+	if (drm_WARN_ON(&ptdev->base, !is_valid_domain(domain)))
+		return -EINVAL;
+
+	switch (cmd) {
+	case PWR_COMMAND_POWER_DOWN:
+		expected_val = 0;
+		break;
+	case PWR_COMMAND_POWER_UP:
+		expected_val = mask;
+		break;
+	default:
+		drm_err(&ptdev->base, "Invalid power domain transition command (0x%x)", cmd);
+		return -EINVAL;
+	}
+
+	ret = panthor_pwr_domain_wait_transition(ptdev, domain, timeout_us);
+	if (ret)
+		return ret;
+
+	/* domain already in target state, return early */
+	if ((gpu_read64(ptdev, ready_reg) & mask) == expected_val)
+		return 0;
+
+	panthor_pwr_write_command(ptdev, pwr_cmd, mask);
+
+	ret = gpu_read64_poll_timeout(ptdev, ready_reg, val, (mask & val) == expected_val, 100,
+				      timeout_us);
+	if (ret) {
+		drm_err(&ptdev->base,
+			"timeout waiting on %s power domain transition, cmd(0x%x), arg(0x%llx)",
+			get_domain_name(domain), pwr_cmd, mask);
+		panthor_pwr_debug_info_show(ptdev);
+		return ret;
+	}
+
+	return 0;
+}
+
+#define panthor_pwr_domain_power_off(__ptdev, __domain, __mask, __timeout_us)            \
+	panthor_pwr_domain_transition(__ptdev, PWR_COMMAND_POWER_DOWN, __domain, __mask, \
+				      __timeout_us)
+
+#define panthor_pwr_domain_power_on(__ptdev, __domain, __mask, __timeout_us) \
+	panthor_pwr_domain_transition(__ptdev, PWR_COMMAND_POWER_UP, __domain, __mask, __timeout_us)
+
+/**
+ * retract_domain() - Retract control of a domain from MCU
+ * @ptdev: Device.
+ * @domain: Domain to retract the control
+ *
+ * Retracting L2 domain is not expected since it won't be delegated.
+ *
+ * Return: 0 on success or retracted already.
+ *         -EPERM if domain is L2.
+ *         A negative error code otherwise.
+ */
+static int retract_domain(struct panthor_device *ptdev, u32 domain)
+{
+	const u32 pwr_cmd = PWR_COMMAND_DEF(PWR_COMMAND_RETRACT, domain, 0);
+	const u64 pwr_status = gpu_read64(ptdev, PWR_STATUS);
+	const u64 delegated_mask = PWR_STATUS_DOMAIN_DELEGATED(domain);
+	const u64 allow_mask = PWR_STATUS_DOMAIN_ALLOWED(domain);
+	u64 val;
+	int ret;
+
+	if (drm_WARN_ON(&ptdev->base, domain == PWR_COMMAND_DOMAIN_L2))
+		return -EPERM;
+
+	ret = gpu_read64_poll_timeout(ptdev, PWR_STATUS, val, !(PWR_STATUS_RETRACT_PENDING & val),
+				      0, PWR_RETRACT_TIMEOUT_US);
+	if (ret) {
+		drm_err(&ptdev->base, "%s domain retract pending", get_domain_name(domain));
+		return ret;
+	}
+
+	if (!(pwr_status & delegated_mask)) {
+		drm_dbg(&ptdev->base, "%s domain already retracted", get_domain_name(domain));
+		return 0;
+	}
+
+	panthor_pwr_write_command(ptdev, pwr_cmd, 0);
+
+	/*
+	 * On successful retraction
+	 * allow-flag will be set with delegated-flag being cleared.
+	 */
+	ret = gpu_read64_poll_timeout(ptdev, PWR_STATUS, val,
+				      ((delegated_mask | allow_mask) & val) == allow_mask, 10,
+				      PWR_TRANSITION_TIMEOUT_US);
+	if (ret) {
+		drm_err(&ptdev->base, "Retracting %s domain timeout, cmd(0x%x)",
+			get_domain_name(domain), pwr_cmd);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * delegate_domain() - Delegate control of a domain to MCU
+ * @ptdev: Device.
+ * @domain: Domain to delegate the control
+ *
+ * Delegating L2 domain is prohibited.
+ *
+ * Return:
+ * *       0 on success or delegated already.
+ * *       -EPERM if domain is L2.
+ * *       A negative error code otherwise.
+ */
+static int delegate_domain(struct panthor_device *ptdev, u32 domain)
+{
+	const u32 pwr_cmd = PWR_COMMAND_DEF(PWR_COMMAND_DELEGATE, domain, 0);
+	const u64 pwr_status = gpu_read64(ptdev, PWR_STATUS);
+	const u64 allow_mask = PWR_STATUS_DOMAIN_ALLOWED(domain);
+	const u64 delegated_mask = PWR_STATUS_DOMAIN_DELEGATED(domain);
+	u64 val;
+	int ret;
+
+	if (drm_WARN_ON(&ptdev->base, domain == PWR_COMMAND_DOMAIN_L2))
+		return -EPERM;
+
+	/* Already delegated, exit early */
+	if (pwr_status & delegated_mask)
+		return 0;
+
+	/* Check if the command is allowed before delegating. */
+	if (!(pwr_status & allow_mask)) {
+		drm_warn(&ptdev->base, "Delegating %s domain not allowed", get_domain_name(domain));
+		return -EPERM;
+	}
+
+	ret = panthor_pwr_domain_wait_transition(ptdev, domain, PWR_TRANSITION_TIMEOUT_US);
+	if (ret)
+		return ret;
+
+	panthor_pwr_write_command(ptdev, pwr_cmd, 0);
+
+	/*
+	 * On successful delegation
+	 * allow-flag will be cleared with delegated-flag being set.
+	 */
+	ret = gpu_read64_poll_timeout(ptdev, PWR_STATUS, val,
+				      ((delegated_mask | allow_mask) & val) == delegated_mask,
+				      10, PWR_TRANSITION_TIMEOUT_US);
+	if (ret) {
+		drm_err(&ptdev->base, "Delegating %s domain timeout, cmd(0x%x)",
+			get_domain_name(domain), pwr_cmd);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int panthor_pwr_delegate_domains(struct panthor_device *ptdev)
+{
+	int ret;
+
+	if (!ptdev->pwr)
+		return 0;
+
+	ret = delegate_domain(ptdev, PWR_COMMAND_DOMAIN_SHADER);
+	if (ret)
+		return ret;
+
+	ret = delegate_domain(ptdev, PWR_COMMAND_DOMAIN_TILER);
+	if (ret)
+		goto err_retract_shader;
+
+	return 0;
+
+err_retract_shader:
+	retract_domain(ptdev, PWR_COMMAND_DOMAIN_SHADER);
+
+	return ret;
+}
+
+/**
+ * panthor_pwr_domain_force_off - Forcefully power down a domain.
+ * @ptdev: Device.
+ * @domain: Domain to forcefully power down.
+ *
+ * This function will attempt to retract and power off the requested power
+ * domain. However, if retraction fails, the operation is aborted. If power off
+ * fails, the domain will remain retracted and under the host control.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+static int panthor_pwr_domain_force_off(struct panthor_device *ptdev, u32 domain)
+{
+	const u64 domain_ready = gpu_read64(ptdev, get_domain_ready_reg(domain));
+	int ret;
+
+	/* Domain already powered down, early exit. */
+	if (!domain_ready)
+		return 0;
+
+	/* Domain has to be in host control to issue power off command. */
+	ret = retract_domain(ptdev, domain);
+	if (ret)
+		return ret;
+
+	return panthor_pwr_domain_power_off(ptdev, domain, domain_ready, PWR_TRANSITION_TIMEOUT_US);
+}
+
 void panthor_pwr_unplug(struct panthor_device *ptdev)
 {
 	unsigned long flags;
@@ -103,6 +428,59 @@ int panthor_pwr_init(struct panthor_device *ptdev)
 	return 0;
 }

+void panthor_pwr_l2_power_off(struct panthor_device *ptdev)
+{
+	const u64 l2_allow_mask = PWR_STATUS_DOMAIN_ALLOWED(PWR_COMMAND_DOMAIN_L2);
+	const u64 pwr_status = gpu_read64(ptdev, PWR_STATUS);
+
+	/* Abort if L2 power off constraints are not satisfied */
+	if (!(pwr_status & l2_allow_mask)) {
+		drm_warn(&ptdev->base, "Power off L2 domain not allowed");
+		return;
+	}
+
+	/* It is expected that when halting the MCU, it would power down its
+	 * delegated domains. However, an unresponsive or hung MCU may not do
+	 * so, which is why we need to check and retract the domains back into
+	 * host control to be powered down in the right order before powering
+	 * down the L2.
+	 */
+	if (panthor_pwr_domain_force_off(ptdev, PWR_COMMAND_DOMAIN_TILER))
+		return;
+
+	if (panthor_pwr_domain_force_off(ptdev, PWR_COMMAND_DOMAIN_SHADER))
+		return;
+
+	panthor_pwr_domain_power_off(ptdev, PWR_COMMAND_DOMAIN_L2, ptdev->gpu_info.l2_present,
+				     PWR_TRANSITION_TIMEOUT_US);
+}
+
+int panthor_pwr_l2_power_on(struct panthor_device *ptdev)
+{
+	const u32 pwr_status = gpu_read64(ptdev, PWR_STATUS);
+	const u32 l2_allow_mask = PWR_STATUS_DOMAIN_ALLOWED(PWR_COMMAND_DOMAIN_L2);
+	int ret;
+
+	if ((pwr_status & l2_allow_mask) == 0) {
+		drm_warn(&ptdev->base, "Power on L2 domain not allowed");
+		return -EPERM;
+	}
+
+	ret = panthor_pwr_domain_power_on(ptdev, PWR_COMMAND_DOMAIN_L2, ptdev->gpu_info.l2_present,
+					  PWR_TRANSITION_TIMEOUT_US);
+	if (ret)
+		return ret;
+
+	/* Delegate control of the shader and tiler power domains to the MCU as
+	 * it can better manage which shader/tiler cores need to be powered up
+	 * or can be powered down based on currently running jobs.
+	 *
+	 * If the shader and tiler domains are already delegated to the MCU,
+	 * this call would just return early.
+	 */
+	return panthor_pwr_delegate_domains(ptdev);
+}
+
 void panthor_pwr_suspend(struct panthor_device *ptdev)
 {
 	if (!ptdev->pwr)
diff --git a/drivers/gpu/drm/panthor/panthor_pwr.h b/drivers/gpu/drm/panthor/panthor_pwr.h
index b325e5b7eba3..3c834059a860 100644
--- a/drivers/gpu/drm/panthor/panthor_pwr.h
+++ b/drivers/gpu/drm/panthor/panthor_pwr.h
@@ -10,6 +10,10 @@ void panthor_pwr_unplug(struct panthor_device *ptdev);

 int panthor_pwr_init(struct panthor_device *ptdev);

+void panthor_pwr_l2_power_off(struct panthor_device *ptdev);
+
+int panthor_pwr_l2_power_on(struct panthor_device *ptdev);
+
 void panthor_pwr_suspend(struct panthor_device *ptdev);

 void panthor_pwr_resume(struct panthor_device *ptdev);
diff --git a/drivers/gpu/drm/panthor/panthor_regs.h b/drivers/gpu/drm/panthor/panthor_regs.h
index 5469eec02178..18702d7001e2 100644
--- a/drivers/gpu/drm/panthor/panthor_regs.h
+++ b/drivers/gpu/drm/panthor/panthor_regs.h
@@ -72,6 +72,7 @@

 #define GPU_FEATURES					0x60
 #define   GPU_FEATURES_RAY_INTERSECTION			BIT(2)
+#define   GPU_FEATURES_RAY_TRAVERSAL			BIT(5)

 #define GPU_TIMESTAMP_OFFSET				0x88
 #define GPU_CYCLE_COUNT					0x90
--
2.49.0

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