drm/xe/topology: Add a function to find the index of the last enabled DSS in a mask

Last enabled DSS in a DSS mask can help estimate the maximum DSSes enabled
in the DSS mask, as the enabled DSSes can be discontiguous.

Reviewed-by: Ashutosh Dixit <[e-mail]>
Signed-off-by: Harish Chegondi <[e-mail]>
Signed-off-by: Ashutosh Dixit <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/79944bb[e-mail]

drivers/gpu/drm/xe/xe_gt_topology.h

···
 
 void xe_gt_topology_dump(struct xe_gt *gt, struct drm_printer *p);
 
+/**
+ * xe_gt_topology_mask_last_dss() - Returns the index of the last DSS in a mask.
+ * @mask: Input DSS mask
+ *
+ * Return: Index of the last DSS in the input DSS mask,
+ *	   XE_MAX_DSS_FUSE_BITS if DSS mask is empty.
+ */
+static inline unsigned int
+xe_gt_topology_mask_last_dss(const xe_dss_mask_t mask)
+{
+	return find_last_bit(mask, XE_MAX_DSS_FUSE_BITS);
+}
+
 unsigned int
 xe_dss_mask_group_ffs(const xe_dss_mask_t mask, int groupsize, int groupnum);