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: 45832bf9c10f3 ("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>

diff --git a/drivers/gpu/drm/xe/xe_late_bind_fw.c b/drivers/gpu/drm/xe/xe_late_bind_fw.c
index 8f5082e689dc8e49570ac4c6e68b0d49acae0c4f..768442ca7da6d832f722835b893e9a927c815911 100644 (file)
--- a/drivers/gpu/drm/xe/xe_late_bind_fw.c
+++ b/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;