drm/xe: Allow specifying number of extra dwords at the end of wa bb emission

Indirect context setup will need more than one.

Signed-off-by: Tvrtko Ursulin <[e-mail]>
Cc: Lucas De Marchi <[e-mail]>
Reviewed-by: Lucas De Marchi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lucas De Marchi <[e-mail]>

drivers/gpu/drm/xe/xe_lrc.c

···
 	struct xe_lrc		*lrc;
 	struct xe_hw_engine	*hwe;
 	size_t			max_size;
+	size_t                  reserve_dw;
 	unsigned int		offset;
 	const struct bo_setup	*funcs;
 	unsigned int		num_funcs;
···
 		remain -= len;
 
 		/*
-		 * There should always be at least 1 additional dword for
-		 * the end marker
+		 * Caller has asked for at least reserve_dw to remain unused.
 		 */
-		if (len < 0 || xe_gt_WARN_ON(state->lrc->gt, remain < 1))
+		if (len < 0 ||
+		    xe_gt_WARN_ON(state->lrc->gt, remain < state->reserve_dw))
 			goto fail;
 
 		state->ptr += len;
···
 		.lrc = lrc,
 		.hwe = hwe,
 		.max_size = LRC_WA_BB_SIZE,
+		.reserve_dw = 1,
 		.offset = __xe_lrc_wa_bb_offset(lrc),
 		.funcs = funcs,
 		.num_funcs = ARRAY_SIZE(funcs),