[Intel-gfx] [PATCH] drm/i915/gt: prevent forcewake releases during BAR resize

[Andrzej Hajda]

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.

Signed-off-by: Andrzej Hajda <andrzej.hajda at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_region_lmem.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
index 89fdfc67f8d1e0..5a01dc6ca08324 100644
--- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
+++ b/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;
 
@@ -102,6 +103,14 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t
 		return;
 	}
 
+	/*
+	 * 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);
+
 	/* First disable PCI memory decoding references */
 	pci_read_config_dword(pdev, PCI_COMMAND, &pci_cmd);
 	pci_write_config_dword(pdev, PCI_COMMAND,
@@ -111,6 +120,9 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t
 
 	pci_assign_unassigned_bus_resources(pdev->bus);
 	pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd);
+
+	with_intel_runtime_pm(i915->uncore.rpm, wakeref)
+		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) {}
-- 
2.34.1