[PATCH v3 3/7] drm/xe: Add ring start to LRC snapshot

[Matthew Brost <matthew.brost@intel.com>]

Add LRC ring start register to LRC snapshot to verify no LRC register
corruption upon hang. This could be possible if the indirect ring state
was mapped to user space or via an internal KMD memory corruption.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
---
 drivers/gpu/drm/xe/xe_lrc.c | 10 ++++++++++
 drivers/gpu/drm/xe/xe_lrc.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
index cc77e5132157..22e58c6e2a35 100644
--- a/drivers/gpu/drm/xe/xe_lrc.c
+++ b/drivers/gpu/drm/xe/xe_lrc.c
@@ -1061,6 +1061,14 @@ u32 xe_lrc_ring_tail(struct xe_lrc *lrc)
 		return xe_lrc_read_ctx_reg(lrc, CTX_RING_TAIL) & TAIL_ADDR;
 }
 
+static u32 xe_lrc_ring_start(struct xe_lrc *lrc)
+{
+	if (xe_lrc_has_indirect_ring_state(lrc))
+		return xe_lrc_read_indirect_ctx_reg(lrc, INDIRECT_CTX_RING_START);
+	else
+		return xe_lrc_read_ctx_reg(lrc, CTX_RING_START);
+}
+
 void xe_lrc_set_ring_head(struct xe_lrc *lrc, u32 head)
 {
 	if (xe_lrc_has_indirect_ring_state(lrc))
@@ -1641,6 +1649,7 @@ struct xe_lrc_snapshot *xe_lrc_snapshot_capture(struct xe_lrc *lrc)
 	snapshot->head = xe_lrc_ring_head(lrc);
 	snapshot->tail.internal = lrc->ring.tail;
 	snapshot->tail.memory = xe_lrc_ring_tail(lrc);
+	snapshot->start = xe_lrc_ring_start(lrc);
 	snapshot->start_seqno = xe_lrc_start_seqno(lrc);
 	snapshot->seqno = xe_lrc_seqno(lrc);
 	snapshot->lrc_bo = xe_bo_get(lrc->bo);
@@ -1701,6 +1710,7 @@ void xe_lrc_snapshot_print(struct xe_lrc_snapshot *snapshot, struct drm_printer
 	drm_printf(p, "\tLRC Head: (memory) %u\n", snapshot->head);
 	drm_printf(p, "\tLRC Tail: (internal) %u, (memory) %u\n",
 		   snapshot->tail.internal, snapshot->tail.memory);
+	drm_printf(p, "\tRing start: (memory) 0x%08x\n", snapshot->start);
 	drm_printf(p, "\tStart seqno: (memory) %d\n", snapshot->start_seqno);
 	drm_printf(p, "\tSeqno: (memory) %d\n", snapshot->seqno);
 	drm_printf(p, "\tTimestamp: 0x%08x\n", snapshot->ctx_timestamp);
diff --git a/drivers/gpu/drm/xe/xe_lrc.h b/drivers/gpu/drm/xe/xe_lrc.h
index 37ca321ed492..b459dcab8787 100644
--- a/drivers/gpu/drm/xe/xe_lrc.h
+++ b/drivers/gpu/drm/xe/xe_lrc.h
@@ -28,6 +28,7 @@ struct xe_lrc_snapshot {
 	u32 ring_addr;
 	u32 indirect_context_desc;
 	u32 head;
+	u32 start;
 	struct {
 		u32 internal;
 		u32 memory;
-- 
2.34.1