[PATCH v2 01/23] drm/xe: Error handling in xe_force_wake_get()

[Himal Prasad Ghimiray]

If an acknowledgment timeout occurs for a domain awake request, do not
increment the reference count for the domain. This ensures that
subsequent _get calls do not incorrectly assume the domain is awake. The
return value is a mask of domains whose reference counts were
incremented, and these domains need to be released using
xe_force_wake_put.

The caller needs to compare the return value with the input domains to
determine the success or failure of the operation and decide whether to
continue or return accordingly.

While at it, add simple kernel-doc for xe_force_wake_get()

Cc: Badal Nilawar <badal.nilawar at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Cc: Nirmoy Das <nirmoy.das at intel.com>
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
---
 drivers/gpu/drm/xe/xe_force_wake.c | 35 +++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_force_wake.c b/drivers/gpu/drm/xe/xe_force_wake.c
index a64c14757c84..fa42d652d23f 100644
--- a/drivers/gpu/drm/xe/xe_force_wake.c
+++ b/drivers/gpu/drm/xe/xe_force_wake.c
@@ -150,26 +150,49 @@ static int domain_sleep_wait(struct xe_gt *gt,
 					 (ffs(tmp__) - 1))) && \
 					 domain__->reg_ctl.addr)
 
+/**
+ * xe_force_wake_get : Increase the domain refcount; if it was 0 initially, wake the domain
+ * @fw: struct xe_force_wake
+ * @domains: forcewake domains to get refcount on
+ *
+ * Increment refcount for the force-wake domain. If the domain is
+ * asleep, awaken it and wait for acknowledgment within the specified
+ * timeout. If a timeout occurs, decrement the refcount.
+ * The caller should compare the return value with the @domains to
+ * determine the success or failure of the operation.
+ *
+ * Return: mask of refcount increased domains. If the return value is
+ * equal to the input parameter @domains, the operation is considered
+ * successful. Otherwise, the operation is considered a failure, and
+ * the caller should handle the failure case, potentially returning
+ * -ETIMEDOUT.
+ */
 int xe_force_wake_get(struct xe_force_wake *fw,
 		      enum xe_force_wake_domains domains)
 {
 	struct xe_gt *gt = fw->gt;
 	struct xe_force_wake_domain *domain;
-	enum xe_force_wake_domains tmp, woken = 0;
+	enum xe_force_wake_domains tmp, awake_rqst = 0, awake_ack = 0;
 	unsigned long flags;
-	int ret = 0;
+	int ret = domains;
 
 	spin_lock_irqsave(&fw->lock, flags);
 	for_each_fw_domain_masked(domain, domains, fw, tmp) {
 		if (!domain->ref++) {
-			woken |= BIT(domain->id);
+			awake_rqst |= BIT(domain->id);
 			domain_wake(gt, domain);
 		}
 	}
-	for_each_fw_domain_masked(domain, woken, fw, tmp) {
-		ret |= domain_wake_wait(gt, domain);
+	for_each_fw_domain_masked(domain, awake_rqst, fw, tmp) {
+		if (domain_wake_wait(gt, domain) == 0) {
+			awake_ack |= BIT(domain->id);
+		} else {
+			ret &= ~BIT(domain->id);
+			--domain->ref;
+		}
 	}
-	fw->awake_domains |= woken;
+
+	fw->awake_domains |= awake_ack;
 	spin_unlock_irqrestore(&fw->lock, flags);
 
 	return ret;
-- 
2.34.1