linux-kernel - [PATCH v3 11/14] remoteproc: Deal with synchronisation when changing FW image

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Message-Id: <20200424200135.28825-12-mathieu.poirier@linaro.org>
Date:   Fri, 24 Apr 2020 14:01:32 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     bjorn.andersson@...aro.org, ohad@...ery.com
Cc:     loic.pallardy@...com, arnaud.pouliquen@...com, s-anna@...com,
        linux-remoteproc@...r.kernel.org, corbet@....net,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 11/14] remoteproc: Deal with synchronisation when changing FW image

This patch prevents the firmware image from being displayed or changed
when the remoteproc core is synchronising with a remote processor. This
is 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@...aro.org>
---
 drivers/remoteproc/remoteproc_sysfs.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
index 7f8536b73295..cdd322a6ecfa 100644
--- a/drivers/remoteproc/remoteproc_sysfs.c
+++ b/drivers/remoteproc/remoteproc_sysfs.c
@@ -13,9 +13,20 @@
 static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
+	ssize_t ret;
 	struct rproc *rproc = to_rproc(dev);
 
-	return sprintf(buf, "%s\n", rproc->firmware);
+	/*
+	 * In most instances there is no guarantee about the firmware
+	 * that was loaded by the external entity.  As such simply don't
+	 * print anything.
+	 */
+	if (rproc_needs_syncing(rproc))
+		ret = sprintf(buf, "\n");
+	else
+		ret = sprintf(buf, "%s\n", rproc->firmware);
+
+	return ret;
 }
 
 /* Change firmware name via sysfs */
@@ -39,6 +50,17 @@ static ssize_t firmware_store(struct device *dev,
 		goto out;
 	}
 
+	/*
+	 * There is no point in trying to change the firmware if loading the
+	 * image of the remote processor is done by another entity.
+	 */
+	if (rproc_needs_syncing(rproc)) {
+		dev_err(dev,
+			"can't change firmware while synchronising with MCU\n");
+		err = -EBUSY;
+		goto out;
+	}
+
 	len = strcspn(buf, "\n");
 	if (!len) {
 		dev_err(dev, "can't provide a NULL firmware\n");
-- 
2.20.1