Subject: Re: [PATCH V7 6/7] remoteproc: imx_rproc: request mbox channel
later

On Mon, Oct 17, 2022 at 03:13:16AM +0000, Peng Fan wrote:

quoted

Hi Mathieu,

quoted

Subject: Re: [PATCH V7 6/7] remoteproc: imx_rproc: request mbox
channel later

On Fri, Oct 14, 2022 at 11:10:36AM +0800, Peng Fan (OSS) wrote:

quoted

From: Peng Fan <peng.fan@nxp.com>

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.

quoted

quoted

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Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/remoteproc/imx_rproc.c | 39
++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/remoteproc/imx_rproc.c

b/drivers/remoteproc/imx_rproc.c index

917e6db39572..1183de84a4c0

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100644

--- a/drivers/remoteproc/imx_rproc.c
+++ b/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
dcfg->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 = {

quoted

 	.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 +745,9 @@ static int imx_rproc_xtr_mbox_init(struct

rproc

*rproc)

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 	struct device *dev = priv->dev;
 	struct mbox_client *cl;

+	if (priv->tx_ch && priv->rx_ch)
+		return 0;
+

You did exactly the same things as in V6.  I asked you why this is
needed and all you did is point me to the code in _probe(), which I can

read on my own.

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Sorry for not wrote down clear.

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Again - why is this needed when we know it will be done in start()
and attach()?

start() and attach() not able to handle mbox defer probe. So I add

We are finally at the heart of the problem.  I had to go look at the
implementation of imx_rproc_xtr_mbox_init() to understand that it can
return -EPROBE_DEFER.  Had there been a comment in the code to highlight
_why_ the if() condition is needed, I would have understood right away and
all this waste of time avoided.

My bad. I could add comment in V8 if no major comments after you review.
Thanks for your time.

Thanks,
Peng.

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the mbox requesting in probe to handle mbox defer probe, and add a
check when requesting mbox channel in start/attach. During first time
attach/start remote core, the imx_rproc_xtr_mbox_init just return,
because channel requested in probe flow.

Since mbox requested in probe, why still add it in start() and attach()?
It is to support runtime stop and start(M4 is under control of Linux),
to support runtime detach(only for i.MX8QM/QXP attach recovery,
m4 out of control from linux) and attach.

Thanks,
Peng.

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 	if (!of_get_property(dev->of_node, "mbox-names", NULL))
 		return 0;

@@ -749,8 +777,15 @@ 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)
--
2.37.1

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