[PATCH V2 13/20] accel/amdxdna: Prepare for AIE4 command submission

[David Zhang <yidong.zhang@amd.com>]

Prepare the data structures and completion wait helpers required for
AIE4 command submission:
- Define struct amdxdna_cmd_start_dpu in amdxdna_ctx.h for the
  ERT_START_DPU payload.
- Extend union amdxdna_job_priv with an aie4 member for queue list
  linkage and job state tracking.
- Implement smp_rmb() ordering and non-sleeping retry in
  get_read_index(), returning the cached last_read_index instead of
  zero when a torn read is detected.
- Update check_cmd_done() and aie4_cmd_wait() to detect asynchronous
  device disconnect and reset via check_cert_comp_linked().

Co-developed-by: Max Zhen <max.zhen@amd.com>
Signed-off-by: Max Zhen <max.zhen@amd.com>
Co-developed-by: Wendy Liang <wendy.liang@amd.com>
Signed-off-by: Wendy Liang <wendy.liang@amd.com>
Signed-off-by: David Zhang <yidong.zhang@amd.com>
---
 drivers/accel/amdxdna/aie4_ctx.c    | 59 ++++++++++++++++++++---------
 drivers/accel/amdxdna/amdxdna_ctx.h | 20 ++++++++++
 2 files changed, 61 insertions(+), 18 deletions(-)

diff --git a/drivers/accel/amdxdna/aie4_ctx.c b/drivers/accel/amdxdna/aie4_ctx.c
index 226570367f71..0672aba7c195 100644
--- a/drivers/accel/amdxdna/aie4_ctx.c
+++ b/drivers/accel/amdxdna/aie4_ctx.c
@@ -394,34 +394,52 @@ static inline bool valid_queue_index(u64 read, u64 write, u32 capacity)
 
 static u64 get_read_index(struct amdxdna_hwctx *hwctx)
 {
-	u64 wi = READ_ONCE(*hwctx->priv->umq_write_index);
-	u64 ri = READ_ONCE(*hwctx->priv->umq_read_index);
+	struct amdxdna_hwctx_priv *priv = hwctx->priv;
 	struct amdxdna_dev *xdna = hwctx->client->xdna;
+	u64 ri, wi;
 
-	/*
-	 * CERT cannot update read index as uint64 atomically. Driver may read
-	 * half-updated read index when it has bits in high 32bit. In case read
-	 * index is not valid, wait for some time and retry once. It should
-	 * allow CERT to complete the read index update.
-	 */
+	/* Sample read_index before write_index to guarantee wi >= ri. */
+	ri = READ_ONCE(*priv->umq_read_index);
+	/* Order the read_index sample before the write_index sample. */
+	smp_rmb();
+	wi = READ_ONCE(priv->write_index);
+
+	/* Non-atomic 64-bit counter update by CERT; re-sample once if invalid. */
 	if (!valid_queue_index(ri, wi, CTX_MAX_CMDS)) {
-		XDNA_WARN(xdna, "Invalid index, ri %llu, wi %llu", ri, wi);
-		usleep_range(100, 200);
-		ri = READ_ONCE(*hwctx->priv->umq_read_index);
+		ri = READ_ONCE(*priv->umq_read_index);
+		/* Order the read_index sample before the write_index sample. */
+		smp_rmb();
+		wi = READ_ONCE(priv->write_index);
 		if (!valid_queue_index(ri, wi, CTX_MAX_CMDS)) {
-			XDNA_ERR(xdna, "Invalid index after retry, ri %llu, wi %llu", ri, wi);
-			ri = 0;
+			/* Fall back to cached read_index if sample is still invalid. */
+			XDNA_DBG(xdna, "Invalid index, ri %llu, wi %llu", ri, wi);
+			return READ_ONCE(priv->last_read_index);
 		}
 	}
 
+	/*
+	 * Cache valid sample as fallback for torn reads. Lockless on purpose:
+	 * a racing caller may store an older value, which only delays seeing
+	 * a completion until the next wakeup, never reports one early.
+	 */
+	WRITE_ONCE(priv->last_read_index, ri);
 	return ri;
 }
 
-static inline bool check_cmd_done(struct amdxdna_hwctx *hwctx, u64 seq)
+/* Verify cert_comp remains linked to detect disconnect or reset. */
+static bool check_cert_comp_linked(struct amdxdna_hwctx *hwctx, struct cert_comp *comp)
 {
-	u64 read_idx = get_read_index(hwctx);
+	/* READ_ONCE pairs with the link/unlink WRITE_ONCE. */
+	return comp == READ_ONCE(hwctx->priv->cert_comp);
+}
 
-	return read_idx > seq;
+static inline bool check_cmd_done(struct amdxdna_hwctx *hwctx, u64 seq, struct cert_comp *comp)
+{
+	/* Lockless check for wait_event condition; detects completion or disconnect. */
+	if (!check_cert_comp_linked(hwctx, comp))
+		return true;
+
+	return get_read_index(hwctx) > seq;
 }
 
 int aie4_cmd_wait(struct amdxdna_hwctx *hwctx, u64 seq, u32 timeout)
@@ -437,11 +455,16 @@ int aie4_cmd_wait(struct amdxdna_hwctx *hwctx, u64 seq, u32 timeout)
 		wait_jifs = msecs_to_jiffies(timeout);
 
 	ret = wait_event_interruptible_timeout(cert_comp->waitq,
-					       (check_cmd_done(hwctx, seq)),
+					       check_cmd_done(hwctx, seq, cert_comp),
 					       wait_jifs);
 
-	if (!ret)
+	if (!ret) {
 		ret = -ETIME;
+	} else if (ret > 0 && !check_cert_comp_linked(hwctx, cert_comp) &&
+		   get_read_index(hwctx) <= seq) {
+		/* Disconnect (suspend or TDR) before the command completed. */
+		ret = -EAGAIN;
+	}
 
 	aie4_put_cert_comp(cert_comp);
 
diff --git a/drivers/accel/amdxdna/amdxdna_ctx.h b/drivers/accel/amdxdna/amdxdna_ctx.h
index 9bbc3db4ebde..b3677851d1c5 100644
--- a/drivers/accel/amdxdna/amdxdna_ctx.h
+++ b/drivers/accel/amdxdna/amdxdna_ctx.h
@@ -48,6 +48,18 @@ struct amdxdna_cmd_start_npu {
 	u32 prop_args[];  /* properties and regular kernel arguments */
 };
 
+/*
+ * struct amdxdna_cmd_start_dpu - interpretation of data payload for
+ * ERT_START_DPU in amdxdna_cmd.
+ */
+struct amdxdna_cmd_start_dpu {
+	u64 dtrace_buffer;		/* dtrace buffer address 2 words */
+	u64 instruction_buffer;		/* buffer address 2 words */
+	u32 instruction_buffer_size;	/* size of buffer in bytes */
+	u16 uc_index;			/* microblaze controller index */
+	u16 chained;			/* number of following amdxdna_cmd_start_dpu elements */
+};
+
 /*
  * Interpretation of the beginning of data payload for ERT_CMD_CHAIN in
  * amdxdna_cmd. The rest of the payload in amdxdna_cmd is cmd BO handles.
@@ -138,8 +150,14 @@ struct amdxdna_drv_cmd {
 };
 
 struct app_health_report;
+
 union amdxdna_job_priv {
 	struct app_health_report *aie2_health;
+	/* aie4 kernel submission: queue linkage + job state */
+	struct {
+		struct list_head	list;
+		u32			state;
+	} aie4;
 };
 
 struct amdxdna_sched_job {
@@ -162,6 +180,8 @@ struct amdxdna_sched_job {
 };
 
 #define aie2_job_health priv.aie2_health
+#define aie4_job_list	priv.aie4.list
+#define aie4_job_state	priv.aie4.state
 
 static inline u32
 amdxdna_cmd_get_op(struct amdxdna_gem_obj *abo)
-- 
2.34.1