Register SCP core 1 as a subdevice of core 0 for the boot sequence
and watchdog timeout handling. The core 1 has to boot after core 0
because the SCP clock and SRAM power is controlled by SCP core 0.
As for watchdog timeout handling, the remoteproc framework helps to
stop/start subdevices automatically when SCP driver receives watchdog
timeout event.

Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/remoteproc/mtk_common.h |  9 +++++
 drivers/remoteproc/mtk_scp.c    | 66 +++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/drivers/remoteproc/mtk_common.h b/drivers/remoteproc/mtk_common.h
index 7821cb15d6fd..d333cefc29da 100644
--- a/drivers/remoteproc/mtk_common.h
+++ b/drivers/remoteproc/mtk_common.h
@@ -112,6 +112,13 @@ struct mtk_scp_of_data {
 	size_t ipi_buf_offset;
 };
 
+struct mtk_scp_core_subdev {
+	struct rproc_subdev subdev;
+	struct mtk_scp *scp;
+};
+
+#define to_core_subdev(d) container_of(d, struct mtk_scp_core_subdev, subdev)
+
 struct mtk_scp {
 	struct device *dev;
 	struct rproc *rproc;
@@ -144,6 +151,8 @@ struct mtk_scp {
 	struct list_head elem;
 	struct list_head cluster_cores;
 	struct list_head *cluster;
+
+	struct mtk_scp_core_subdev *core_subdev;
 };
 
 /**
diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
index 6588e5acb159..be995c88d333 100644
--- a/drivers/remoteproc/mtk_scp.c
+++ b/drivers/remoteproc/mtk_scp.c
@@ -861,6 +861,60 @@ static void scp_remove_rpmsg_subdev(struct mtk_scp *scp)
 	}
 }
 
+static int scp_core_subdev_start(struct rproc_subdev *subdev)
+{
+	struct mtk_scp_core_subdev *core_subdev = to_core_subdev(subdev);
+	struct mtk_scp *scp = core_subdev->scp;
+
+	rproc_boot(scp->rproc);
+
+	return 0;
+}
+
+static void scp_core_subdev_stop(struct rproc_subdev *subdev, bool crashed)
+{
+	struct mtk_scp_core_subdev *core_subdev = to_core_subdev(subdev);
+	struct mtk_scp *scp = core_subdev->scp;
+
+	rproc_shutdown(scp->rproc);
+}
+
+static int scp_core_subdev_register(struct mtk_scp *scp)
+{
+	struct device *dev = scp->dev;
+	struct mtk_scp_core_subdev *core_subdev;
+	struct mtk_scp *scp_c0;
+
+	scp_c0 = list_first_entry(scp->cluster, struct mtk_scp, elem);
+	if (!scp_c0)
+		return -ENODATA;
+
+	core_subdev = devm_kzalloc(dev, sizeof(*core_subdev), GFP_KERNEL);
+	if (!core_subdev)
+		return -ENOMEM;
+
+	core_subdev->scp = scp;
+	core_subdev->subdev.start = scp_core_subdev_start;
+	core_subdev->subdev.stop = scp_core_subdev_stop;
+
+	scp->core_subdev = core_subdev;
+	rproc_add_subdev(scp_c0->rproc, &scp->core_subdev->subdev);
+
+	return 0;
+}
+
+static void scp_core_subdev_unregister(struct mtk_scp *scp)
+{
+	struct mtk_scp *scp_c0;
+
+	if (scp->core_subdev) {
+		scp_c0 = list_first_entry(scp->cluster, struct mtk_scp, elem);
+		rproc_remove_subdev(scp_c0->rproc, &scp->core_subdev->subdev);
+		devm_kfree(scp->dev, scp->core_subdev);
+		scp->core_subdev = NULL;
+	}
+}
+
 static int scp_rproc_init(struct platform_device *pdev,
 			  struct mtk_scp_of_regs *of_regs,
 			  const struct mtk_scp_of_data *of_data,
@@ -958,6 +1012,7 @@ static void scp_rproc_free(struct mtk_scp *scp)
 {
 	int i;
 
+	scp_core_subdev_unregister(scp);
 	scp_remove_rpmsg_subdev(scp);
 	scp_ipi_unregister(scp, SCP_IPI_INIT);
 	scp_unmap_memory_region(scp);
@@ -1034,6 +1089,17 @@ static int scp_cluster_init(struct platform_device *pdev,
 	}
 
 	list_for_each_entry_safe_reverse(scp, temp, cluster, elem) {
+		if (!list_is_first(&scp->elem, cluster)) {
+			ret = scp_core_subdev_register(scp);
+			if (ret) {
+				dev_err_probe(scp->dev, ret, "Failed to register as subdev\n");
+				goto add_fail;
+			}
+
+			/* sub cores are booted as subdevices of core 0 */
+			scp->rproc->auto_boot = false;
+		}
+
 		ret = rproc_add(scp->rproc);
 		if (ret)
 			goto add_fail;
-- 
2.18.0