[PATCH 2/2] drm/xe/lrc: Prepare WA BB setup for more users

[Umesh Nerlige Ramappa]

On Wed, Jun 04, 2025 at 08:03:06AM -0700, Lucas De Marchi wrote:
>The post context restore (WA BB) is a mechanism in HW that may be used
>for things other than the utilization setup. Create a new function
>called setup_wa_bb() that wraps any function writing useful commands in
>the buffer.
>
>Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>

LGTM,

Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>

Thanks,
Umesh

>---
> drivers/gpu/drm/xe/xe_lrc.c | 69 ++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 55 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
>index bf7c3981897de..529c6a972a55b 100644
>--- a/drivers/gpu/drm/xe/xe_lrc.c
>+++ b/drivers/gpu/drm/xe/xe_lrc.c
>@@ -914,9 +914,8 @@ static void xe_lrc_finish(struct xe_lrc *lrc)
> }
>
> /*
>- * xe_lrc_setup_utilization() - Setup wa bb to assist in calculating active
>- * context run ticks.
>- * @lrc: Pointer to the lrc.
>+ * wa_bb_setup_utilization() - Write commands to wa bb to assist
>+ * in calculating active context run ticks.
>  *
>  * Context Timestamp (CTX_TIMESTAMP) in the LRC accumulates the run ticks of the
>  * context, but only gets updated when the context switches out. In order to
>@@ -941,18 +940,13 @@ static void xe_lrc_finish(struct xe_lrc *lrc)
>  * store it in the PPHSWP.
>  */
> #define CONTEXT_ACTIVE 1ULL
>-static int xe_lrc_setup_utilization(struct xe_lrc *lrc)
>+static ssize_t wa_bb_setup_utilization(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
>+				       u32 *batch, size_t max_len)
> {
>-	u32 *cmd, *buf = NULL;
>+	u32 *cmd = batch;
>
>-	if (lrc->bb_per_ctx_bo->vmap.is_iomem) {
>-		buf = kmalloc(lrc->bb_per_ctx_bo->size, GFP_KERNEL);
>-		if (!buf)
>-			return -ENOMEM;
>-		cmd = buf;
>-	} else {
>-		cmd = lrc->bb_per_ctx_bo->vmap.vaddr;
>-	}
>+	if (xe_gt_WARN_ON(lrc->gt, max_len < 12))
>+		return -ENOSPC;
>
> 	*cmd++ = MI_STORE_REGISTER_MEM | MI_SRM_USE_GGTT | MI_SRM_ADD_CS_OFFSET;
> 	*cmd++ = ENGINE_ID(0).addr;
>@@ -971,6 +965,49 @@ static int xe_lrc_setup_utilization(struct xe_lrc *lrc)
> 		*cmd++ = upper_32_bits(CONTEXT_ACTIVE);
> 	}
>
>+	return cmd - batch;
>+}
>+
>+struct wa_bb_setup {
>+	ssize_t (*setup)(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
>+			 u32 *batch, size_t max_size);
>+};
>+
>+static int setup_wa_bb(struct xe_lrc *lrc, struct xe_hw_engine *hwe)
>+{
>+	const size_t max_size = lrc->bb_per_ctx_bo->size;
>+	static const struct wa_bb_setup funcs[] = {
>+		{ .setup = wa_bb_setup_utilization },
>+	};
>+	ssize_t remain;
>+	u32 *cmd, *buf = NULL;
>+
>+	if (lrc->bb_per_ctx_bo->vmap.is_iomem) {
>+		buf = kmalloc(max_size, GFP_KERNEL);
>+		if (!buf)
>+			return -ENOMEM;
>+		cmd = buf;
>+	} else {
>+		cmd = lrc->bb_per_ctx_bo->vmap.vaddr;
>+	}
>+
>+	remain = max_size / sizeof(*cmd);
>+
>+	for (size_t i = 0; i < ARRAY_SIZE(funcs); i++) {
>+		ssize_t len = funcs[i].setup(lrc, hwe, cmd, remain);
>+
>+		remain -= len;
>+
>+		/*
>+		 * There should always be at least 1 additional dword for
>+		 * the end marker
>+		 */
>+		if (len < 0 || xe_gt_WARN_ON(lrc->gt, remain < 1))
>+			goto fail;
>+
>+		cmd += len;
>+	}
>+
> 	*cmd++ = MI_BATCH_BUFFER_END;
>
> 	if (buf) {
>@@ -983,6 +1020,10 @@ static int xe_lrc_setup_utilization(struct xe_lrc *lrc)
> 			     xe_bo_ggtt_addr(lrc->bb_per_ctx_bo) | 1);
>
> 	return 0;
>+
>+fail:
>+	kfree(buf);
>+	return -ENOSPC;
> }
>
> #define PVC_CTX_ASID		(0x2e + 1)
>@@ -1139,7 +1180,7 @@ static int xe_lrc_init(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
> 	map = __xe_lrc_start_seqno_map(lrc);
> 	xe_map_write32(lrc_to_xe(lrc), &map, lrc->fence_ctx.next_seqno - 1);
>
>-	err = xe_lrc_setup_utilization(lrc);
>+	err = setup_wa_bb(lrc, hwe);
> 	if (err)
> 		goto err_lrc_finish;
>
>
>-- 
>2.49.0
>