remoteproc: imx_rproc: Request mbox channel later

It is possible that when remote processor crash, the communication
channel will be broken with garbage value in mailbox, such as
when Linux is issuing a message through mailbox, remote processor
crashes, we need free & rebuild the mailbox channels to make sure
no garbage value in mailbox channels.

So move the request/free to start/stop for managing remote procesosr in
Linux, move to attach/detach for remote processor is out of control of
Linux.

Previous, we just request mbox when attach for CM4 boot early before
Linux, but if mbox defer probe, remoteproc core will do resource cleanup
and corrupt resource table for later probe.

So move request mbox ealier and still keep mbox request when attach
for self recovery case, but keep a check when request/free mbox.
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20221021041526.3696483-7-peng.fan@oss.nxp.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/imx_rproc.c

@@ -84,6 +84,8 @@ struct imx_rproc_mem {
 #define ATT_CORE_MASK   0xffff
 #define ATT_CORE(I)     BIT((I))
 
+static int imx_rproc_xtr_mbox_init(struct rproc *rproc);
+static void imx_rproc_free_mbox(struct rproc *rproc);
 static int imx_rproc_detach_pd(struct rproc *rproc);
 
 struct imx_rproc {
@@ -357,6 +359,10 @@ static int imx_rproc_start(struct rproc *rproc)
 	struct arm_smccc_res res;
 	int ret;
 
+	ret = imx_rproc_xtr_mbox_init(rproc);
+	if (ret)
+		return ret;
+
 	switch (dcfg->method) {
 	case IMX_RPROC_MMIO:
 		ret = regmap_update_bits(priv->regmap, dcfg->src_reg, dcfg->src_mask,
@@ -407,6 +413,8 @@ static int imx_rproc_stop(struct rproc *rproc)
 
 	if (ret)
 		dev_err(dev, "Failed to stop remote core\n");
+	else
+		imx_rproc_free_mbox(rproc);
 
 	return ret;
 }
@@ -592,6 +600,22 @@ static void imx_rproc_kick(struct rproc *rproc, int vqid)
 
 static int imx_rproc_attach(struct rproc *rproc)
 {
+	return imx_rproc_xtr_mbox_init(rproc);
+}
+
+static int imx_rproc_detach(struct rproc *rproc)
+{
+	struct imx_rproc *priv = rproc->priv;
+	const struct imx_rproc_dcfg *dcfg = priv->dcfg;
+
+	if (dcfg->method != IMX_RPROC_SCU_API)
+		return -EOPNOTSUPP;
+
+	if (imx_sc_rm_is_resource_owned(priv->ipc_handle, priv->rsrc_id))
+		return -EOPNOTSUPP;
+
+	imx_rproc_free_mbox(rproc);
+
 	return 0;
 }
 
@@ -610,6 +634,7 @@ static struct resource_table *imx_rproc_get_loaded_rsc_table(struct rproc *rproc
 static const struct rproc_ops imx_rproc_ops = {
 	.prepare	= imx_rproc_prepare,
 	.attach		= imx_rproc_attach,
+	.detach		= imx_rproc_detach,
 	.start		= imx_rproc_start,
 	.stop		= imx_rproc_stop,
 	.kick		= imx_rproc_kick,
@@ -720,6 +745,18 @@ static int imx_rproc_xtr_mbox_init(struct rproc *rproc)
 	struct device *dev = priv->dev;
 	struct mbox_client *cl;
 
+	/*
+	 * stop() and detach() will free the mbox channels, so need
+	 * to request mbox channels in start() and attach().
+	 *
+	 * Because start() and attach() not able to handle mbox defer
+	 * probe, imx_rproc_xtr_mbox_init is also called in probe().
+	 * The check is to avoid request mbox again when start() or
+	 * attach() after probe() returns success.
+	 */
+	if (priv->tx_ch && priv->rx_ch)
+		return 0;
+
 	if (!of_get_property(dev->of_node, "mbox-names", NULL))
 		return 0;
 
@@ -749,8 +786,15 @@ static void imx_rproc_free_mbox(struct rproc *rproc)
 {
 	struct imx_rproc *priv = rproc->priv;
 
-	mbox_free_channel(priv->tx_ch);
-	mbox_free_channel(priv->rx_ch);
+	if (priv->tx_ch) {
+		mbox_free_channel(priv->tx_ch);
+		priv->tx_ch = NULL;
+	}
+
+	if (priv->rx_ch) {
+		mbox_free_channel(priv->rx_ch);
+		priv->rx_ch = NULL;
+	}
 }
 
 static void imx_rproc_put_scu(struct rproc *rproc)