[PATCH 1/2] drm/xe/lrc: Use a temporary buffer for WA BB

[Umesh Nerlige Ramappa]

On Wed, Jun 04, 2025 at 08:03:05AM -0700, Lucas De Marchi wrote:
>In case the BO is in iomem, we can't simply take the vaddr and write to
>it. Instead, prepare a separate buffer that is later copied into io
>memory. Right now it's just a few words that could be using
>xe_map_write32(), but the intention is to grow the WA BB for other
>uses.
>
>Fixes: 82b98cadb01f ("drm/xe: Add WA BB to capture active context utilization")
>Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
>Cc: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
>Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>

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

Thanks,
Umesh
>---
> drivers/gpu/drm/xe/xe_lrc.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
>index 63d74e27f54cf..bf7c3981897de 100644
>--- a/drivers/gpu/drm/xe/xe_lrc.c
>+++ b/drivers/gpu/drm/xe/xe_lrc.c
>@@ -941,11 +941,18 @@ static void xe_lrc_finish(struct xe_lrc *lrc)
>  * store it in the PPHSWP.
>  */
> #define CONTEXT_ACTIVE 1ULL
>-static void xe_lrc_setup_utilization(struct xe_lrc *lrc)
>+static int xe_lrc_setup_utilization(struct xe_lrc *lrc)
> {
>-	u32 *cmd;
>+	u32 *cmd, *buf = NULL;
>
>-	cmd = lrc->bb_per_ctx_bo->vmap.vaddr;
>+	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;
>+	}
>
> 	*cmd++ = MI_STORE_REGISTER_MEM | MI_SRM_USE_GGTT | MI_SRM_ADD_CS_OFFSET;
> 	*cmd++ = ENGINE_ID(0).addr;
>@@ -966,9 +973,16 @@ static void xe_lrc_setup_utilization(struct xe_lrc *lrc)
>
> 	*cmd++ = MI_BATCH_BUFFER_END;
>
>+	if (buf) {
>+		xe_map_memcpy_to(gt_to_xe(lrc->gt), &lrc->bb_per_ctx_bo->vmap, 0,
>+				 buf, (cmd - buf) * sizeof(*cmd));
>+		kfree(buf);
>+	}
>+
> 	xe_lrc_write_ctx_reg(lrc, CTX_BB_PER_CTX_PTR,
> 			     xe_bo_ggtt_addr(lrc->bb_per_ctx_bo) | 1);
>
>+	return 0;
> }
>
> #define PVC_CTX_ASID		(0x2e + 1)
>@@ -1125,7 +1139,9 @@ 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);
>
>-	xe_lrc_setup_utilization(lrc);
>+	err = xe_lrc_setup_utilization(lrc);
>+	if (err)
>+		goto err_lrc_finish;
>
> 	return 0;
>
>
>-- 
>2.49.0
>