remoteproc: Refactor function rproc_trigger_auto_boot()

Refactor function rproc_trigger_auto_boot() to properly deal
with scenarios where the remoteproc core needs to attach with a
remote processor that has already been booted by an external
entity.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20200714195035.1426873-8-mathieu.poirier@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1571,6 +1571,15 @@ static int rproc_trigger_auto_boot(struct rproc *rproc)
 {
 	int ret;
 
+	/*
+	 * Since the remote processor is in a detached state, it has already
+	 * been booted by another entity.  As such there is no point in waiting
+	 * for a firmware image to be loaded, we can simply initiate the process
+	 * of attaching to it immediately.
+	 */
+	if (rproc->state == RPROC_DETACHED)
+		return rproc_boot(rproc);
+
 	/*
 	 * We're initiating an asynchronous firmware loading, so we can
 	 * be built-in kernel code, without hanging the boot process.