[PATCH v7 10/17] 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.poir...@linaro.org>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliq...@st.com>
---
 drivers/remoteproc/remoteproc_core.c | 58 +++++++++++++++++++++++++++-
 include/linux/remoteproc.h           |  1 +
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_core.c 
b/drivers/remoteproc/remoteproc_core.c
index f2a005eadfd5..5eaa47c3ba92 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -1709,7 +1709,7 @@ 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;
@@ -1948,6 +1948,62 @@ 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_attach()).
+ *
+ * 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 the remote proc is still needed, bail out */
+       if (!atomic_dec_and_test(&rproc->power)) {
+               ret = 0;
+               goto out;
+       }
+
+       ret = __rproc_detach(rproc);
+       if (ret) {
+               atomic_inc(&rproc->power);
+               goto out;
+       }
+
+       /* clean up all acquired resources */
+       rproc_resource_cleanup(rproc);
+
+       /* release HW resources if needed */
+       rproc_unprepare_device(rproc);
+
+       rproc_disable_iommu(rproc);
+
+       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 eff55ec72e80..e1c843c19cc6 100644
--- a/include/linux/remoteproc.h
+++ b/include/linux/remoteproc.h
@@ -662,6 +662,7 @@ 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);
 void rproc_coredump_using_sections(struct rproc *rproc);
-- 
2.25.1