drm/i915/gt: prevent forcewake releases during BAR resize

Tests on DG2 machines show that releasing forcewakes during BAR resize
results later in forcewake ack timeouts. Since forcewakes can be realeased
asynchronously the simplest way to prevent it is to get all forcewakes
for duration of BAR resizing.

v2: hold rpm as well during resizing (Rodrigo)

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6530
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/7853Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230308133624.2131582-1-andrzej.hajda@intel.com

drivers/gpu/drm/i915/gt/intel_region_lmem.c

@@ -54,6 +54,7 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t
 	struct resource *root_res;
 	resource_size_t rebar_size;
 	resource_size_t current_size;
+	intel_wakeref_t wakeref;
 	u32 pci_cmd;
 	int i;
 
@@ -102,15 +103,25 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t
 		return;
 	}
 
-	/* First disable PCI memory decoding references */
-	pci_read_config_dword(pdev, PCI_COMMAND, &pci_cmd);
-	pci_write_config_dword(pdev, PCI_COMMAND,
-			       pci_cmd & ~PCI_COMMAND_MEMORY);
+	/*
+	 * Releasing forcewake during BAR resizing results in later forcewake
+	 * ack timeouts and former can happen any time - it is asynchronous.
+	 * Grabbing all forcewakes prevents it.
+	 */
+	with_intel_runtime_pm(i915->uncore.rpm, wakeref) {
+		intel_uncore_forcewake_get(&i915->uncore, FORCEWAKE_ALL);
 
-	_resize_bar(i915, GEN12_LMEM_BAR, rebar_size);
+		/* First disable PCI memory decoding references */
+		pci_read_config_dword(pdev, PCI_COMMAND, &pci_cmd);
+		pci_write_config_dword(pdev, PCI_COMMAND,
+				       pci_cmd & ~PCI_COMMAND_MEMORY);
 
-	pci_assign_unassigned_bus_resources(pdev->bus);
-	pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd);
+		_resize_bar(i915, GEN12_LMEM_BAR, rebar_size);
+
+		pci_assign_unassigned_bus_resources(pdev->bus);
+		pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd);
+		intel_uncore_forcewake_put(&i915->uncore, FORCEWAKE_ALL);
+	}
 }
 #else
 static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t lmem_size) {}