[PATCH RFC v2 09/11] remoteproc: imx_rproc: always use non-blocking mailboxes

[Francesco Valla <francesco@valla.it>]

Blocking mailboxes may lead to sleep during the kick operation, which
conflicts with some virtio devices (e.g.: virtio-can) that kicks their
virtqueues with spinlock(s) held.

Align to the behavior of all the other remoteproc drivers that use a
mailbox to perform the kick (i.e.: omap, st, stm32, ti_k3_*, xlnx_r5)
and move to a non-blocking mailbox here as well. Messages need to be
allocated and freed on-the-fly, since they might be sent after
imx_rproc_kick() returns and cannot thus live on the stack.

As a side effect of this modification, the close-reopen action on
the mailboxes during restart and shutdown can be removed, since it was
performed only to have a non-blocking mailbox.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 drivers/remoteproc/imx_rproc.c | 76 ++++++++++++++++--------------------------
 drivers/remoteproc/imx_rproc.h |  1 -
 2 files changed, 28 insertions(+), 49 deletions(-)

diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
index 581bb07f5893..a792b9ca5edd 100644
--- a/drivers/remoteproc/imx_rproc.c
+++ b/drivers/remoteproc/imx_rproc.c
@@ -96,7 +96,7 @@ struct imx_rproc_mem {
 /* Linux has permission to handle the Logical Machine of remote cores */
 #define IMX_RPROC_FLAGS_SM_LMM_CTRL	BIT(0)
 
-static int imx_rproc_xtr_mbox_init(struct rproc *rproc, bool tx_block);
+static int imx_rproc_xtr_mbox_init(struct rproc *rproc);
 static void imx_rproc_free_mbox(void *data);
 
 /* Forward declarations for platform operations */
@@ -441,7 +441,7 @@ static int imx_rproc_start(struct rproc *rproc)
 	struct device *dev = priv->dev;
 	int ret;
 
-	ret = imx_rproc_xtr_mbox_init(rproc, true);
+	ret = imx_rproc_xtr_mbox_init(rproc);
 	if (ret)
 		return ret;
 
@@ -696,28 +696,45 @@ static void imx_rproc_kick(struct rproc *rproc, int vqid)
 {
 	struct imx_rproc *priv = rproc->priv;
 	int err;
-	__u32 mmsg;
+	__u32 *mmsg;
 
 	if (!priv->tx_ch) {
 		dev_err(priv->dev, "No initialized mbox tx channel\n");
 		return;
 	}
 
+	mmsg = kzalloc_obj(*mmsg, GFP_ATOMIC);
+	if (!mmsg) {
+		dev_err_ratelimited(priv->dev, "cannot allocate kick message\n");
+		return;
+	}
+
 	/*
 	 * Send the index of the triggered virtqueue as the mu payload.
 	 * Let remote processor know which virtqueue is used.
 	 */
-	mmsg = vqid << 16;
+	*mmsg = vqid << 16;
 
-	err = mbox_send_message(priv->tx_ch, (void *)&mmsg);
-	if (err < 0)
+	err = mbox_send_message(priv->tx_ch, (void *)mmsg);
+	if (err < 0) {
 		dev_err(priv->dev, "%s: failed (%d, err:%d)\n",
 			__func__, vqid, err);
+		kfree(mmsg);
+	}
+}
+
+static void imx_rproc_kick_tx_done(struct mbox_client *cl, void *mmsg, int r)
+{
+	if (r != 0)
+		dev_err_ratelimited(cl->dev, "failed to kick vqid %u: %d\n",
+				    *(__u32 *)mmsg >> 16, r);
+
+	kfree(mmsg);
 }
 
 static int imx_rproc_attach(struct rproc *rproc)
 {
-	return imx_rproc_xtr_mbox_init(rproc, true);
+	return imx_rproc_xtr_mbox_init(rproc);
 }
 
 static int imx_rproc_scu_api_detach(struct rproc *rproc)
@@ -872,7 +889,7 @@ static void imx_rproc_rx_callback(struct mbox_client *cl, void *msg)
 	idr_for_each(&rproc->notifyids, imx_rproc_notified_idr_cb, rproc);
 }
 
-static int imx_rproc_xtr_mbox_init(struct rproc *rproc, bool tx_block)
+static int imx_rproc_xtr_mbox_init(struct rproc *rproc)
 {
 	struct imx_rproc *priv = rproc->priv;
 	struct device *dev = priv->dev;
@@ -895,10 +912,10 @@ static int imx_rproc_xtr_mbox_init(struct rproc *rproc, bool tx_block)
 
 	cl = &priv->cl;
 	cl->dev = dev;
-	cl->tx_block = tx_block;
-	cl->tx_tout = 100;
+	cl->tx_block = false;
 	cl->knows_txdone = false;
 	cl->rx_callback = imx_rproc_rx_callback;
+	cl->tx_done = imx_rproc_kick_tx_done;
 
 	priv->tx_ch = mbox_request_channel_byname(cl, "tx");
 	if (IS_ERR(priv->tx_ch))
@@ -1218,22 +1235,6 @@ static int imx_rproc_detect_mode(struct imx_rproc *priv)
 	return priv->ops->detect_mode(priv->rproc);
 }
 
-static int imx_rproc_sys_off_handler(struct sys_off_data *data)
-{
-	struct rproc *rproc = data->cb_data;
-	int ret;
-
-	imx_rproc_free_mbox(rproc);
-
-	ret = imx_rproc_xtr_mbox_init(rproc, false);
-	if (ret) {
-		dev_err(&rproc->dev, "Failed to request non-blocking mbox\n");
-		return NOTIFY_BAD;
-	}
-
-	return NOTIFY_DONE;
-}
-
 static int imx_rproc_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1262,7 +1263,7 @@ static int imx_rproc_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(dev, rproc);
 
-	ret = imx_rproc_xtr_mbox_init(rproc, true);
+	ret = imx_rproc_xtr_mbox_init(rproc);
 	if (ret)
 		return ret;
 
@@ -1292,26 +1293,6 @@ static int imx_rproc_probe(struct platform_device *pdev)
 	if (rproc->state != RPROC_DETACHED)
 		rproc->auto_boot = of_property_read_bool(np, "fsl,auto-boot");
 
-	if (dcfg->flags & IMX_RPROC_NEED_SYSTEM_OFF) {
-		/*
-		 * setup mailbox to non-blocking mode in
-		 * [SYS_OFF_MODE_POWER_OFF_PREPARE, SYS_OFF_MODE_RESTART_PREPARE]
-		 * phase before invoking [SYS_OFF_MODE_POWER_OFF, SYS_OFF_MODE_RESTART]
-		 * atomic chain, see kernel/reboot.c.
-		 */
-		ret = devm_register_sys_off_handler(dev, SYS_OFF_MODE_POWER_OFF_PREPARE,
-						    SYS_OFF_PRIO_DEFAULT,
-						    imx_rproc_sys_off_handler, rproc);
-		if (ret)
-			return dev_err_probe(dev, ret, "register power off handler failure\n");
-
-		ret = devm_register_sys_off_handler(dev, SYS_OFF_MODE_RESTART_PREPARE,
-						    SYS_OFF_PRIO_DEFAULT,
-						    imx_rproc_sys_off_handler, rproc);
-		if (ret)
-			return dev_err_probe(dev, ret, "register restart handler failure\n");
-	}
-
 	pm_runtime_enable(dev);
 	ret = pm_runtime_resume_and_get(dev);
 	if (ret)
@@ -1424,7 +1405,6 @@ static const struct imx_rproc_dcfg imx_rproc_cfg_imx8ulp = {
 static const struct imx_rproc_dcfg imx_rproc_cfg_imx7ulp = {
 	.att		= imx_rproc_att_imx7ulp,
 	.att_size	= ARRAY_SIZE(imx_rproc_att_imx7ulp),
-	.flags		= IMX_RPROC_NEED_SYSTEM_OFF,
 };
 
 static const struct imx_rproc_dcfg imx_rproc_cfg_imx7d = {
diff --git a/drivers/remoteproc/imx_rproc.h b/drivers/remoteproc/imx_rproc.h
index 0d7d48352a10..9a1400d0d081 100644
--- a/drivers/remoteproc/imx_rproc.h
+++ b/drivers/remoteproc/imx_rproc.h
@@ -16,7 +16,6 @@ struct imx_rproc_att {
 };
 
 /* dcfg flags */
-#define IMX_RPROC_NEED_SYSTEM_OFF	BIT(0)
 #define IMX_RPROC_NEED_CLKS		BIT(1)
 
 struct imx_rproc_plat_ops {

-- 
2.56.0