linux-kernel - [PATCH 7/8] bus: fsl-mc: rescan devices if endpoint not found

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Date:   Thu, 15 Jul 2021 17:07:17 +0300
From:   laurentiu.tudor@....com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Cc:     diana.craciun@....com, ioana.ciornei@....com, jon@...id-run.com,
        leoyang.li@....com, Laurentiu Tudor <laurentiu.tudor@....com>,
        Robert-Ionut Alexa <robert-ionut.alexa@....com>
Subject: [PATCH 7/8] bus: fsl-mc: rescan devices if endpoint not found

From: Laurentiu Tudor <laurentiu.tudor@....com>

If the endpoint of a device is not yet probed on the bus, force
a rescan of the devices and retry to get a reference to the
endpoint device. If the device is still not found then we assume
it's in a different isolation context (container/DPRC) thus
unavailable and return a permission error.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
Signed-off-by: Robert-Ionut Alexa <robert-ionut.alexa@....com>
---
 drivers/bus/fsl-mc/fsl-mc-bus.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index e5b4830cf3c5..31595017d207 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -950,10 +950,28 @@ struct fsl_mc_device *fsl_mc_get_endpoint(struct fsl_mc_device *mc_dev)
 	 * We know that the device has an endpoint because we verified by
 	 * interrogating the firmware. This is the case when the device was not
 	 * yet discovered by the fsl-mc bus, thus the lookup returned NULL.
-	 * Differentiate this case by returning EPROBE_DEFER.
+	 * Force a rescan of the devices in this container and retry the lookup.
+	 */
+	if (!endpoint) {
+		struct fsl_mc_bus *mc_bus = to_fsl_mc_bus(mc_bus_dev);
+
+		if (mutex_trylock(&mc_bus->scan_mutex)) {
+			err = dprc_scan_objects(mc_bus_dev, true);
+			mutex_unlock(&mc_bus->scan_mutex);
+		}
+
+		if (err < 0)
+			return ERR_PTR(err);
+	}
+
+	endpoint = fsl_mc_device_lookup(&endpoint_desc, mc_bus_dev);
+	/*
+	 * This means that the endpoint might reside in a different isolation
+	 * context (DPRC/container). Not much to do, so return a permssion
+	 * error.
 	 */
 	if (!endpoint)
-		return ERR_PTR(-EPROBE_DEFER);
+		return ERR_PTR(-EPERM);
 
 	return endpoint;
 }
-- 
2.17.1