[PATCH v4 12/17] remoteproc: Introduce function rproc_detach()

[Mathieu Poirier]

Introduce function rproc_detach() to enable the remoteproc
core to release the resources associated with a remote processor
without stopping its operation.

Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Reviewed-by: Peng Fan <peng.fan@xxxxxxx>
---
 drivers/remoteproc/remoteproc_core.c | 71 +++++++++++++++++++++++++++-
 include/linux/remoteproc.h           |  2 +
 2 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index e665ed4776c3..ece3f15070b9 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -1673,7 +1673,7 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 /*
  * __rproc_detach(): Does the opposite of rproc_attach()
  */
-static int __maybe_unused __rproc_detach(struct rproc *rproc)
+static int __rproc_detach(struct rproc *rproc)
 {
 	struct device *dev = &rproc->dev;
 	int ret;
@@ -1927,6 +1927,75 @@ void rproc_shutdown(struct rproc *rproc)
 }
 EXPORT_SYMBOL(rproc_shutdown);
 
+/**
+ * rproc_detach() - Detach the remote processor from the
+ * remoteproc core
+ *
+ * @rproc: the remote processor
+ *
+ * Detach a remote processor (previously attached to with rproc_actuate()).
+ *
+ * In case @rproc is still being used by an additional user(s), then
+ * this function will just decrement the power refcount and exit,
+ * without disconnecting the device.
+ *
+ * Function rproc_detach() calls __rproc_detach() in order to let a remote
+ * processor know that services provided by the application processor are
+ * no longer available.  From there it should be possible to remove the
+ * platform driver and even power cycle the application processor (if the HW
+ * supports it) without needing to switch off the remote processor.
+ */
+int rproc_detach(struct rproc *rproc)
+{
+	struct device *dev = &rproc->dev;
+	int ret;
+
+	ret = mutex_lock_interruptible(&rproc->lock);
+	if (ret) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
+		return ret;
+	}
+
+	if (rproc->state != RPROC_RUNNING && rproc->state != RPROC_ATTACHED) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	/* if the remote proc is still needed, bail out */
+	if (!atomic_dec_and_test(&rproc->power)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	ret = __rproc_detach(rproc);
+	if (ret) {
+		atomic_inc(&rproc->power);
+		goto out;
+	}
+
+	/* clean up all acquired resources */
+	rproc_resource_cleanup(rproc);
+
+	rproc_disable_iommu(rproc);
+
+	/*
+	 * If the remote processor was booted by the core the cached table needs
+	 * to be freed and ->table_ptr set to NULL because it will be
+	 * invalidated by rproc_resource_cleanup().  If the remote processor was
+	 * attached to ->cached_table is NULL and kfree() returns right away.
+	 *
+	 * In either case ->table_ptr has to be set to NULL.  It will be set
+	 * again when the remote processor is re-attached to.
+	 */
+	kfree(rproc->cached_table);
+	rproc->cached_table = NULL;
+	rproc->table_ptr = NULL;
+out:
+	mutex_unlock(&rproc->lock);
+	return ret;
+}
+EXPORT_SYMBOL(rproc_detach);
+
 /**
  * rproc_get_by_phandle() - find a remote processor by phandle
  * @phandle: phandle to the rproc
diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
index 9bb34c3eb847..65ece6f177b7 100644
--- a/include/linux/remoteproc.h
+++ b/include/linux/remoteproc.h
@@ -659,6 +659,8 @@ rproc_of_resm_mem_entry_init(struct device *dev, u32 of_resm_idx, size_t len,
 
 int rproc_boot(struct rproc *rproc);
 void rproc_shutdown(struct rproc *rproc);
+int rproc_detach(struct rproc *rproc);
+int rproc_set_firmware(struct rproc *rproc, const char *fw_name);
 void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type);
 int rproc_coredump_add_segment(struct rproc *rproc, dma_addr_t da, size_t size);
 int rproc_coredump_add_custom_segment(struct rproc *rproc,
-- 
2.25.1