[Intel-xe] [PATCH v3 1/5] drm/xe: hold mem_access.ref for CT fast-path

[Matthew Auld]

Just checking xe_device_mem_access_ongoing() is not enough, we also need
to hold the reference otherwise the ref can transition from 1 -> 0 as we
enter g2h_read(), leading to warnings. While we can't do a full rpm sync
in the IRQ, we can keep the device awake if the ref is non-zero.
Introduce a new helper for this and set it to work in for the CT
fast-path.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: José Roberto de Souza <jose.souza at intel.com>
---
 drivers/gpu/drm/xe/xe_device.c | 5 +++++
 drivers/gpu/drm/xe/xe_device.h | 1 +
 drivers/gpu/drm/xe/xe_guc_ct.c | 5 ++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 07ae208af809..94b0089b0dee 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -412,6 +412,11 @@ u32 xe_device_ccs_bytes(struct xe_device *xe, u64 size)
 		DIV_ROUND_UP(size, NUM_BYTES_PER_CCS_BYTE) : 0;
 }
 
+bool xe_device_mem_access_get_if_ongoing(struct xe_device *xe)
+{
+	return atomic_inc_not_zero(&xe->mem_access.ref);
+}
+
 void xe_device_mem_access_get(struct xe_device *xe)
 {
 	bool resumed = xe_pm_runtime_resume_if_suspended(xe);
diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
index 779f71d066e6..8e01bbadb149 100644
--- a/drivers/gpu/drm/xe/xe_device.h
+++ b/drivers/gpu/drm/xe/xe_device.h
@@ -138,6 +138,7 @@ static inline struct xe_force_wake * gt_to_fw(struct xe_gt *gt)
 }
 
 void xe_device_mem_access_get(struct xe_device *xe);
+bool xe_device_mem_access_get_if_ongoing(struct xe_device *xe);
 void xe_device_mem_access_put(struct xe_device *xe);
 
 static inline bool xe_device_mem_access_ongoing(struct xe_device *xe)
diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index 22bc9ce846db..b7aecc480098 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -1038,7 +1038,8 @@ void xe_guc_ct_fast_path(struct xe_guc_ct *ct)
 	struct xe_device *xe = ct_to_xe(ct);
 	int len;
 
-	if (!xe_device_in_fault_mode(xe) || !xe_device_mem_access_ongoing(xe))
+	if (!xe_device_in_fault_mode(xe) ||
+	    !xe_device_mem_access_get_if_ongoing(xe))
 		return;
 
 	spin_lock(&ct->fast_lock);
@@ -1048,6 +1049,8 @@ void xe_guc_ct_fast_path(struct xe_guc_ct *ct)
 			g2h_fast_path(ct, ct->fast_msg, len);
 	} while (len > 0);
 	spin_unlock(&ct->fast_lock);
+
+	xe_device_mem_access_put(xe);
 }
 
 /* Returns less than zero on error, 0 on done, 1 on more available */
-- 
2.41.0