drm/xe/xe_late_bind_fw: Initialize uval variable in xe_late_bind_fw_num_fans()

Initialize the uval variable to 0 in xe_late_bind_fw_num_fans() to fix
a potential use of uninitialized variable warning and ensure predictable
behavior.

The variable is passed by reference to xe_pcode_read() which should
populate it on success, but initializing it to 0 provides a safe
default value and follows kernel coding best practices.

v2:
- uval = 0 which serves as both a safe default and the fallback
  value when the pcode read operation fails.

v3:
- Handle MMIO failure (Rodrigo)
- The function should probably return the error and make the uval as
  pointer-argument, like the pcode_read.
- Change the caller of this function to propagate the error
  upwards if mmio failed.

Fixes: 45832bf ("drm/xe/xe_late_bind_fw: Initialize late binding firmware")
Signed-off-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
Link: https://lore.kernel.org/r/20251002005648.3185636-1-mallesh.koujalagi@intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit 07abc16c14693df703763c45e9fc0abfefc927d5)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Author: Mallesh-Koujalagi

drivers/gpu/drm/xe/xe_late_bind_fw.c

@@ -184,17 +184,13 @@ static const char *xe_late_bind_parse_status(uint32_t status)
 	}
 }
 
-static int xe_late_bind_fw_num_fans(struct xe_late_bind *late_bind)
+static int xe_late_bind_fw_num_fans(struct xe_late_bind *late_bind, u32 *num_fans)
 {
 	struct xe_device *xe = late_bind_to_xe(late_bind);
 	struct xe_tile *root_tile = xe_device_get_root_tile(xe);
-	u32 uval;
 
-	if (!xe_pcode_read(root_tile,
-			   PCODE_MBOX(FAN_SPEED_CONTROL, FSC_READ_NUM_FANS, 0), &uval, NULL))
-		return uval;
-	else
-		return 0;
+	return xe_pcode_read(root_tile,
+			     PCODE_MBOX(FAN_SPEED_CONTROL, FSC_READ_NUM_FANS, 0), num_fans, NULL);
 }
 
 void xe_late_bind_wait_for_worker_completion(struct xe_late_bind *late_bind)
@@ -314,7 +310,11 @@ static int __xe_late_bind_fw_init(struct xe_late_bind *late_bind, u32 fw_id)
 	lb_fw->flags &= ~INTEL_LB_FLAG_IS_PERSISTENT;
 
 	if (lb_fw->type == INTEL_LB_TYPE_FAN_CONTROL) {
-		num_fans = xe_late_bind_fw_num_fans(late_bind);
+		ret = xe_late_bind_fw_num_fans(late_bind, &num_fans);
+		if (ret) {
+			drm_dbg(&xe->drm, "Failed to read number of fans: %d\n", ret);
+			return 0; /* Not a fatal error, continue without fan control */
+		}
 		drm_dbg(&xe->drm, "Number of Fans: %d\n", num_fans);
 		if (!num_fans)
 			return 0;