Re: [PATCH v2] drm/i915/gt: prevent forcewake releases during BAR resize

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On 08.03.2023 18:29, Das, Nirmoy wrote:

On 3/8/2023 2:36 PM, Andrzej Hajda wrote:
Tests on DG2 machines show that releasing forcewakes during BAR resize
results later in forcewake ack timeouts.
Do we have a fdo/issues url for that? Having that as References would be nice.

The patch is result of issue reported internally, but...grepping bugtracker I've found potential candidates:

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6530
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/7853

Maybe it would be good to add them on merge.
Anyway thx for a-b.

Regards
Andrzej

  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)

Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>


Acked-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>


---
Please ignore resend of v1, my mistake.

Regards
Andrzej
---
  drivers/gpu/drm/i915/gt/intel_region_lmem.c | 25 +++++++++++++++------
  1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
index 89fdfc67f8d1e0..2a3217e2890fc7 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;
@@ -102,15 +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) {}




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