[PATCH 1/3] ASoC: qcom: q6apm: Wait for SPF to be ready before registering

[Shawn Guo <shengchao.guo@oss.qualcomm.com>]

apm_probe() sends APM_CMD_GET_SPF_STATE once and ignores the result.
At cold boot this is harmless: module loading and PDR lookup delay the
probe by tens of milliseconds after the DSP is up, so SPF is listening
by the time the command is sent.

After an ADSP restart, everything is already loaded and PDR reports the
audio PD up at once. The GPR service is added about 0.5 ms after the
remoteproc reports the DSP up, and SPF drops a command sent that early
without replying:

  remoteproc remoteproc0: remote processor adsp is now up
  qcom,apr ...: Adding APR/GPR dev: gprsvc:service:2:1
  qcom-apm gprsvc:service:2:1: CMD timeout for [1001021] opcode

Once the q6apm component is registered, a sound card whose other
components are still bound can bind right away, inside apm_probe(), and
issue APM_CMD_SHARED_MEM_MAP_REGIONS before SPF can handle it. The map
times out and the card fails to come up:

  qcom-apm gprsvc:service:2:1: CMD timeout for [100100c] opcode

Poll GET_SPF_STATE before registering the component. Simply retrying
q6apm_get_apm_state() is not enough: it goes through
audioreach_send_cmd_sync(), whose 5 second timeout makes every dropped
command stall the probe, and the card with it, for 5 seconds. Instead,
send the command directly and wait only 100 ms for the reply, for up to
5 seconds in total, which is the worst case of the single command sent
before. A timed out try is retried at once, while a "not ready" reply
or a send failure backs off for 100 ms first. On Nord, SPF answers
within 100-200 ms of the restart. If it still does not answer, warn and
carry on as before rather than failing the probe.

Signed-off-by: Shawn Guo <shengchao.guo@oss.qualcomm.com>
---
 sound/soc/qcom/qdsp6/q6apm.c | 50 +++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/sound/soc/qcom/qdsp6/q6apm.c b/sound/soc/qcom/qdsp6/q6apm.c
index 4cb597d737b1..e7ba6bc93142 100644
--- a/sound/soc/qcom/qdsp6/q6apm.c
+++ b/sound/soc/qcom/qdsp6/q6apm.c
@@ -26,6 +26,8 @@ struct apm_graph_mgmt_cmd {
 } __packed;
 
 #define APM_GRAPH_MGMT_PSIZE(p, n) ALIGN(struct_size(p, sub_graph_id_list, n), 8)
+#define Q6APM_SPF_POLL_MS	100
+#define Q6APM_SPF_READY_MS	5000
 
 static struct q6apm *g_apm;
 
@@ -154,6 +156,47 @@ static int q6apm_get_apm_state(struct q6apm *apm)
 	return apm->state;
 }
 
+/*
+ * Right after the DSP boots, the SPF drops commands without replying. Poll
+ * GET_SPF_STATE with a short timeout per try instead of the 5 s one of
+ * q6apm_send_cmd_sync(), so a dropped command does not stall the probe.
+ */
+static bool q6apm_wait_spf_ready(struct q6apm *apm)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(Q6APM_SPF_READY_MS);
+	gpr_device_t *gdev = apm->gdev;
+
+	do {
+		struct gpr_pkt *pkt __free(kfree) =
+			audioreach_alloc_apm_cmd_pkt(0, APM_CMD_GET_SPF_STATE, 0);
+		long rc;
+
+		if (IS_ERR(pkt))
+			return false;
+
+		pkt->hdr.dest_domain = audioreach_gpr_dest_domain(gdev);
+
+		mutex_lock(&apm->lock);
+		apm->result.opcode = 0;
+		apm->state = 0;
+		rc = gpr_send_pkt(gdev, pkt);
+		if (rc >= 0)
+			rc = wait_event_timeout(apm->wait,
+					apm->result.opcode == APM_CMD_RSP_GET_SPF_STATE,
+					msecs_to_jiffies(Q6APM_SPF_POLL_MS));
+		mutex_unlock(&apm->lock);
+
+		if (apm->state)
+			return true;
+
+		/* A timeout has already waited, anything else backs off */
+		if (rc)
+			msleep(Q6APM_SPF_POLL_MS);
+	} while (time_before(jiffies, timeout));
+
+	return false;
+}
+
 bool q6apm_is_adsp_ready(void)
 {
 	if (g_apm)
@@ -906,7 +949,12 @@ static int apm_probe(gpr_device_t *gdev)
 	dev_set_drvdata(dev, apm);
 	g_apm = apm;
 
-	q6apm_get_apm_state(apm);
+	/*
+	 * Once the component is registered a card can bind and send commands
+	 * at once, so wait for the SPF first.
+	 */
+	if (!q6apm_wait_spf_ready(apm))
+		dev_warn(dev, "SPF not ready\n");
 
 	ret = snd_soc_register_component(dev, &q6apm_audio_component, NULL, 0);
 	if (ret < 0) {
-- 
2.43.0