[PATCH 4/4] remoteproc: k3-r5: support for graceful stop of remote cores

[Richard Genoud <richard.genoud@xxxxxxxxxxx>]

Introduce software IPC handshake between the K3-R5 remote proc driver
and the R5 MCU to gracefully stop/reset the remote core.

Upon a stop request, K3-R5 remote proc driver sends a RP_MBOX_SHUTDOWN
mailbox message to the remote R5 core.
The remote core is expected to:
- relinquish all the resources acquired through Device Manager (DM)
- disable its interrupts
- send back a mailbox acknowledgment RP_MBOX_SHUDOWN_ACK
- enter WFI state.

Meanwhile, the K3-R5 remote proc driver does:
- wait for the RP_MBOX_SHUTDOWN_ACK from the remote core
- wait for the remote proc to enter WFI state
- reset the remote core through device manager

Based on work from: Hari Nagalla <hnagalla@xxxxxx>

Signed-off-by: Richard Genoud <richard.genoud@xxxxxxxxxxx>
---
 drivers/remoteproc/omap_remoteproc.h     |  9 +++++-
 drivers/remoteproc/ti_k3_r5_remoteproc.c | 40 ++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/omap_remoteproc.h b/drivers/remoteproc/omap_remoteproc.h
index 828e13256c02..c008f11fa2a4 100644
--- a/drivers/remoteproc/omap_remoteproc.h
+++ b/drivers/remoteproc/omap_remoteproc.h
@@ -42,6 +42,11 @@
  * @RP_MBOX_SUSPEND_CANCEL: a cancel suspend response from a remote processor
  * on a suspend request
  *
+ * @RP_MBOX_SHUTDOWN: shutdown request for the remote processor
+ *
+ * @RP_MBOX_SHUTDOWN_ACK: successful response from remote processor for a
+ * shutdown request. The remote processor should be in WFI state short after.
+ *
  * Introduce new message definitions if any here.
  *
  * @RP_MBOX_END_MSG: Indicates end of known/defined messages from remote core
@@ -59,7 +64,9 @@ enum omap_rp_mbox_messages {
 	RP_MBOX_SUSPEND_SYSTEM	= 0xFFFFFF11,
 	RP_MBOX_SUSPEND_ACK	= 0xFFFFFF12,
 	RP_MBOX_SUSPEND_CANCEL	= 0xFFFFFF13,
-	RP_MBOX_END_MSG		= 0xFFFFFF14,
+	RP_MBOX_SHUTDOWN	= 0xFFFFFF14,
+	RP_MBOX_SHUTDOWN_ACK	= 0xFFFFFF15,
+	RP_MBOX_END_MSG		= 0xFFFFFF16,
 };
 
 #endif /* _OMAP_RPMSG_H */
diff --git a/drivers/remoteproc/ti_k3_r5_remoteproc.c b/drivers/remoteproc/ti_k3_r5_remoteproc.c
index a2ead87952c7..918a15e1dd9a 100644
--- a/drivers/remoteproc/ti_k3_r5_remoteproc.c
+++ b/drivers/remoteproc/ti_k3_r5_remoteproc.c
@@ -21,6 +21,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/remoteproc.h>
 #include <linux/suspend.h>
+#include <linux/iopoll.h>
 #include <linux/reset.h>
 #include <linux/slab.h>
 
@@ -172,8 +173,23 @@ struct k3_r5_rproc {
 	struct k3_r5_core *core;
 	struct k3_r5_mem *rmem;
 	int num_rmems;
+	struct completion shutdown_complete;
 };
 
+/*
+ * This will return true if the remote core is in Wait For Interrupt state.
+ */
+static bool k3_r5_is_core_in_wfi(struct k3_r5_core *core)
+{
+	int ret;
+	u64 boot_vec;
+	u32 cfg, ctrl, stat;
+
+	ret = ti_sci_proc_get_status(core->tsp, &boot_vec, &cfg, &ctrl, &stat);
+
+	return !ret ? !!(stat & PROC_BOOT_STATUS_FLAG_R5_WFI) : false;
+}
+
 /**
  * k3_r5_rproc_mbox_callback() - inbound mailbox message handler
  * @client: mailbox client pointer used for requesting the mailbox channel
@@ -209,6 +225,10 @@ static void k3_r5_rproc_mbox_callback(struct mbox_client *client, void *data)
 	case RP_MBOX_ECHO_REPLY:
 		dev_info(dev, "received echo reply from %s\n", name);
 		break;
+	case RP_MBOX_SHUTDOWN_ACK:
+		dev_dbg(dev, "received shutdown_ack from %s\n", name);
+		complete(&kproc->shutdown_complete);
+		break;
 	default:
 		/* silently handle all other valid messages */
 		if (msg >= RP_MBOX_READY && msg < RP_MBOX_END_MSG)
@@ -634,6 +654,7 @@ static int k3_r5_rproc_stop(struct rproc *rproc)
 	struct k3_r5_cluster *cluster = kproc->cluster;
 	struct device *dev = kproc->dev;
 	struct k3_r5_core *core1, *core = kproc->core;
+	bool wfi;
 	int ret;
 
 
@@ -650,6 +671,24 @@ static int k3_r5_rproc_stop(struct rproc *rproc)
 		}
 	}
 
+	/* Send SHUTDOWN message to remote proc */
+	reinit_completion(&kproc->shutdown_complete);
+	ret = mbox_send_message(kproc->mbox, (void *)RP_MBOX_SHUTDOWN);
+	if (ret < 0) {
+		dev_err(dev, "Sending SHUTDOWN message failed: %d. Halting core anyway.\n", ret);
+	} else {
+		ret = wait_for_completion_timeout(&kproc->shutdown_complete,
+						  msecs_to_jiffies(1000));
+		if (ret == 0) {
+			dev_err(dev, "Timeout waiting SHUTDOWN_ACK message. Halting core anyway.\n");
+		} else {
+			ret = readx_poll_timeout(k3_r5_is_core_in_wfi, core,
+						 wfi, wfi, 200, 2000);
+			if (ret)
+				dev_err(dev, "Timeout waiting for remote proc to be in WFI state. Halting core anyway.\n");
+		}
+	}
+
 	/* halt all applicable cores */
 	if (cluster->mode == CLUSTER_MODE_LOCKSTEP) {
 		list_for_each_entry(core, &cluster->cores, elem) {
@@ -1410,6 +1449,7 @@ static int k3_r5_cluster_rproc_init(struct platform_device *pdev)
 			goto err_config;
 		}
 
+		init_completion(&kproc->shutdown_complete);
 init_rmem:
 		k3_r5_adjust_tcm_sizes(kproc);