From: Ville Syrjälä <[email protected]>

We use forcewake to prevent the SoC from actually entering
PC8 while performing the PC8 disable sequence. Hide that
behind a new parent interface to eliminate the naked
forcewake/uncore usage from the display power code.

v2: Mark the interface optional and warn if
    someone calls it when not provided (Jani)
    Include the header to make sure the extern
    declaration matches the definition (Jani)

Cc: Jani Nikula <[email protected]>
Signed-off-by: Ville Syrjälä <[email protected]>
---
 drivers/gpu/drm/i915/Makefile                 |  1 +
 .../drm/i915/display/intel_display_power.c    |  8 ++---
 drivers/gpu/drm/i915/display/intel_parent.c   | 17 ++++++++++
 drivers/gpu/drm/i915/display/intel_parent.h   |  3 ++
 drivers/gpu/drm/i915/i915_display_pc8.c       | 31 +++++++++++++++++++
 drivers/gpu/drm/i915/i915_display_pc8.h       |  9 ++++++
 drivers/gpu/drm/i915/i915_driver.c            |  2 ++
 include/drm/intel/display_parent_interface.h  |  8 +++++
 8 files changed, 75 insertions(+), 4 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/i915_display_pc8.c
 create mode 100644 drivers/gpu/drm/i915/i915_display_pc8.h

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 175bd99e1d0d..b57e51d626b1 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -76,6 +76,7 @@ i915-$(CONFIG_PERF_EVENTS) += \
 
 # core display adaptation
 i915-y += \
+       i915_display_pc8.o \
        i915_hdcp_gsc.o
 
 # "Graphics Technology" (aka we talk to the gpu)
diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c 
b/drivers/gpu/drm/i915/display/intel_display_power.c
index 9f323c39d798..47042a4c3a30 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -1339,10 +1339,10 @@ static void hsw_restore_lcpll(struct intel_display 
*display)
                return;
 
        /*
-        * Make sure we're not on PC8 state before disabling PC8, otherwise
-        * we'll hang the machine. To prevent PC8 state, just enable force_wake.
+        * Make sure we're not on PC8 state before disabling
+        * PC8, otherwise we'll hang the machine.
         */
-       intel_uncore_forcewake_get(&dev_priv->uncore, FORCEWAKE_ALL);
+       intel_parent_pc8_block(display);
 
        if (val & LCPLL_POWER_DOWN_ALLOW) {
                val &= ~LCPLL_POWER_DOWN_ALLOW;
@@ -1372,7 +1372,7 @@ static void hsw_restore_lcpll(struct intel_display 
*display)
                                "Switching back to LCPLL failed\n");
        }
 
-       intel_uncore_forcewake_put(&dev_priv->uncore, FORCEWAKE_ALL);
+       intel_parent_pc8_unblock(display);
 
        intel_update_cdclk(display);
        intel_cdclk_dump_config(display, &display->cdclk.hw, "Current CDCLK");
diff --git a/drivers/gpu/drm/i915/display/intel_parent.c 
b/drivers/gpu/drm/i915/display/intel_parent.c
index 2ea310cc3509..ceb8ceea4ba4 100644
--- a/drivers/gpu/drm/i915/display/intel_parent.c
+++ b/drivers/gpu/drm/i915/display/intel_parent.c
@@ -17,6 +17,7 @@
  * function pointer interface.
  */
 
+#include <drm/drm_print.h>
 #include <drm/intel/display_parent_interface.h>
 
 #include "intel_display_core.h"
@@ -56,6 +57,22 @@ void intel_parent_irq_synchronize(struct intel_display 
*display)
        display->parent->irq->synchronize(display->drm);
 }
 
+void intel_parent_pc8_block(struct intel_display *display)
+{
+       if (drm_WARN_ON_ONCE(display->drm, !display->parent->pc8))
+               return;
+
+       display->parent->pc8->block(display->drm);
+}
+
+void intel_parent_pc8_unblock(struct intel_display *display)
+{
+       if (drm_WARN_ON_ONCE(display->drm, !display->parent->pc8))
+               return;
+
+       display->parent->pc8->unblock(display->drm);
+}
+
 bool intel_parent_rps_available(struct intel_display *display)
 {
        return display->parent->rps;
diff --git a/drivers/gpu/drm/i915/display/intel_parent.h 
b/drivers/gpu/drm/i915/display/intel_parent.h
index 8f91a6f75c53..974a016ab3be 100644
--- a/drivers/gpu/drm/i915/display/intel_parent.h
+++ b/drivers/gpu/drm/i915/display/intel_parent.h
@@ -22,6 +22,9 @@ void intel_parent_hdcp_gsc_context_free(struct intel_display 
*display,
 bool intel_parent_irq_enabled(struct intel_display *display);
 void intel_parent_irq_synchronize(struct intel_display *display);
 
+void intel_parent_pc8_block(struct intel_display *display);
+void intel_parent_pc8_unblock(struct intel_display *display);
+
 bool intel_parent_rps_available(struct intel_display *display);
 void intel_parent_rps_boost_if_not_started(struct intel_display *display, 
struct dma_fence *fence);
 void intel_parent_rps_mark_interactive(struct intel_display *display, bool 
interactive);
diff --git a/drivers/gpu/drm/i915/i915_display_pc8.c 
b/drivers/gpu/drm/i915/i915_display_pc8.c
new file mode 100644
index 000000000000..2af5dbab20ef
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_display_pc8.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2025, Intel Corporation.
+ */
+
+#include <drm/drm_print.h>
+#include <drm/intel/display_parent_interface.h>
+
+#include "i915_display_pc8.h"
+#include "i915_drv.h"
+#include "intel_uncore.h"
+
+static void i915_display_pc8_block(struct drm_device *drm)
+{
+       struct intel_uncore *uncore = &to_i915(drm)->uncore;
+
+       /* to prevent PC8 state, just enable force_wake */
+       intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
+}
+
+static void i915_display_pc8_unblock(struct drm_device *drm)
+{
+       struct intel_uncore *uncore = &to_i915(drm)->uncore;
+
+       intel_uncore_forcewake_put(uncore, FORCEWAKE_ALL);
+}
+
+const struct intel_display_pc8_interface i915_display_pc8_interface = {
+       .block = i915_display_pc8_block,
+       .unblock = i915_display_pc8_unblock,
+};
diff --git a/drivers/gpu/drm/i915/i915_display_pc8.h 
b/drivers/gpu/drm/i915/i915_display_pc8.h
new file mode 100644
index 000000000000..717f313d2a21
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_display_pc8.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: MIT */
+/* Copyright © 2025 Intel Corporation */
+
+#ifndef __I915_DISPLAY_PC8_H__
+#define __I915_DISPLAY_PC8_H__
+
+extern const struct intel_display_pc8_interface i915_display_pc8_interface;
+
+#endif /* __I915_DISPLAY_PC8_H__ */
diff --git a/drivers/gpu/drm/i915/i915_driver.c 
b/drivers/gpu/drm/i915/i915_driver.c
index d98839427ef9..723cb424b2ba 100644
--- a/drivers/gpu/drm/i915/i915_driver.c
+++ b/drivers/gpu/drm/i915/i915_driver.c
@@ -89,6 +89,7 @@
 #include "pxp/intel_pxp_pm.h"
 
 #include "i915_debugfs.h"
+#include "i915_display_pc8.h"
 #include "i915_driver.h"
 #include "i915_drm_client.h"
 #include "i915_drv.h"
@@ -761,6 +762,7 @@ static const struct intel_display_parent_interface parent = 
{
        .hdcp = &i915_display_hdcp_interface,
        .rpm = &i915_display_rpm_interface,
        .irq = &i915_display_irq_interface,
+       .pc8 = &i915_display_pc8_interface,
        .rps = &i915_display_rps_interface,
        .vgpu_active = vgpu_active,
        .has_fenced_regions = has_fenced_regions,
diff --git a/include/drm/intel/display_parent_interface.h 
b/include/drm/intel/display_parent_interface.h
index 61d1b22adc83..f07d265e90e5 100644
--- a/include/drm/intel/display_parent_interface.h
+++ b/include/drm/intel/display_parent_interface.h
@@ -41,6 +41,11 @@ struct intel_display_irq_interface {
        void (*synchronize)(struct drm_device *drm);
 };
 
+struct intel_display_pc8_interface {
+       void (*block)(struct drm_device *drm);
+       void (*unblock)(struct drm_device *drm);
+};
+
 struct intel_display_rps_interface {
        void (*boost_if_not_started)(struct dma_fence *fence);
        void (*mark_interactive)(struct drm_device *drm, bool interactive);
@@ -69,6 +74,9 @@ struct intel_display_parent_interface {
        /** @irq: IRQ interface */
        const struct intel_display_irq_interface *irq;
 
+       /** @pc8: PC8 interface. Optional. */
+       const struct intel_display_pc8_interface *pc8;
+
        /** @rpm: RPS interface. Optional. */
        const struct intel_display_rps_interface *rps;
 
-- 
2.51.2

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