remoteproc: Properly handle firmware name when attaching

This patch prevents the firmware image name from being displayed when
the remoteproc core is attaching to a remote processor. This is needed
needed since there is no guarantee about the nature of the firmware
image that is loaded by the external entity.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20200714195035.1426873-10-mathieu.poirier@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1627,6 +1627,14 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 
 	rproc->state = RPROC_OFFLINE;
 
+	/*
+	 * The remote processor has been stopped and is now offline, which means
+	 * that the next time it is brought back online the remoteproc core will
+	 * be responsible to load its firmware.  As such it is no longer
+	 * autonomous.
+	 */
+	rproc->autonomous = false;
+
 	dev_info(dev, "stopped remote processor %s\n", rproc->name);
 
 	return 0;
@@ -2145,6 +2153,16 @@ int rproc_add(struct rproc *rproc)
 	/* create debugfs entries */
 	rproc_create_debug_dir(rproc);
 
+	/*
+	 * Remind ourselves the remote processor has been attached to rather
+	 * than booted by the remoteproc core.  This is important because the
+	 * RPROC_DETACHED state will be lost as soon as the remote processor
+	 * has been attached to.  Used in firmware_show() and reset in
+	 * rproc_stop().
+	 */
+	if (rproc->state == RPROC_DETACHED)
+		rproc->autonomous = true;
+
 	/* if rproc is marked always-on, request it to boot */
 	if (rproc->auto_boot) {
 		ret = rproc_trigger_auto_boot(rproc);

drivers/remoteproc/remoteproc_sysfs.c

@@ -15,8 +15,20 @@ static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
 	struct rproc *rproc = to_rproc(dev);
-
-	return sprintf(buf, "%s\n", rproc->firmware);
+	const char *firmware = rproc->firmware;
+
+	/*
+	 * If the remote processor has been started by an external
+	 * entity we have no idea of what image it is running.  As such
+	 * simply display a generic string rather then rproc->firmware.
+	 *
+	 * Here we rely on the autonomous flag because a remote processor
+	 * may have been attached to and currently in a running state.
+	 */
+	if (rproc->autonomous)
+		firmware = "unknown";
+
+	return sprintf(buf, "%s\n", firmware);
 }
 
 /* Change firmware name via sysfs */

include/linux/remoteproc.h

@@ -491,6 +491,7 @@ struct rproc_dump_segment {
  * @table_sz: size of @cached_table
  * @has_iommu: flag to indicate if remote processor is behind an MMU
  * @auto_boot: flag to indicate if remote processor should be auto-started
+ * @autonomous: true if an external entity has booted the remote processor
  * @dump_segments: list of segments in the firmware
  * @nb_vdev: number of vdev currently handled by rproc
  */
@@ -524,6 +525,7 @@ struct rproc {
 	size_t table_sz;
 	bool has_iommu;
 	bool auto_boot;
+	bool autonomous;
 	struct list_head dump_segments;
 	int nb_vdev;
 	u8 elf_class;