Re: [PATCH v4 11/17] remoteproc: Introduce function __rproc_detach()

On Wed, Jan 27, 2021 at 09:46:58AM +0100, Arnaud POULIQUEN wrote:

On 12/18/20 6:32 PM, Mathieu Poirier wrote:

quoted

Introduce function __rproc_detach() to perform the same kind of
operation as rproc_stop(), but instead of switching off the
remote processor using rproc->ops->stop(), it uses
rproc->ops->detach().  That way it is possible for the core
to release the resources associated with a remote processor while
the latter is kept operating.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/remoteproc/remoteproc_core.c | 42 ++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index fc28053c7f89..e665ed4776c3 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c

@@ -1670,6 +1670,48 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 	return 0;
 }
 
+/*
+ * __rproc_detach(): Does the opposite of rproc_attach()
+ */
+static int __maybe_unused __rproc_detach(struct rproc *rproc)
+{
+	struct device *dev = &rproc->dev;
+	int ret;
+
+	/* No need to continue if a detach() operation has not been provided */
+	if (!rproc->ops->detach)
+		return -EINVAL;

I wonder if this ops should be optional.

Function rproc_validate() doesn't check for it so it is optional.  Returning an
error is to indicate to sysfs the operation is not supported if someone tries to
do a "detach" when rproc::ops doesn't provide it.

quoted

+
+	/* Stop any subdevices for the remote processor */
+	rproc_stop_subdevices(rproc, false);
+
+	/*
+	 * If the remote processors was started by the core then a cached_table
+	 * is present and we must follow the same cleanup sequence as we would
+	 * for a shutdown().  As it is in rproc_stop(), use the cached resource
+	 * table for the rest of the detach process since ->table_ptr will
+	 * become invalid as soon as carveouts are released in
+	 * rproc_resource_cleanup().
+	 */
+	if (rproc->cached_table)
+		rproc->table_ptr = rproc->cached_table;
+
+	/* Tell the remote processor the core isn't available anymore */
+	ret = rproc->ops->detach(rproc);
+	if (ret) {
+		dev_err(dev, "can't detach from rproc: %d\n", ret);
+		rproc_start_subdevices(rproc);

Not sure that this would be possible in all cases, without a unprepare and
prepare. What about having the same behavior as the rproc_stop failure?

I thought rproc_stop()'s failure path was buggy and could be improved but as you
say, there might be other ramifications to take into account.  I agree that it
is more prudent to follow the current behavior from rproc_stop() and leave
enhancements for another patchset.

Thanks
Arnaud.

quoted

+		return ret;
+	}
+
+	rproc_unprepare_subdevices(rproc);
+
+	rproc->state = RPROC_DETACHED;
+
+	dev_info(dev, "detached remote processor %s\n", rproc->name);
+
+	return 0;
+}
 
 /**
  * rproc_trigger_recovery() - recover a remoteproc