[PATCH 2/2] drivers: cci: add missing CCI port availability firmware check

[Lorenzo Pieralisi]

The CCI ports programming interface is available to the kernel
only when booted in secure mode (or when firmware enables
non-secure access to override CCI ports control). In both cases,
firmware reports the CCI ports availability through the device
tree CCI ports nodes, which must be parsed and their status checked
by the kernel probing path.

This check is currently missing and may cause the kernel to
erroneously believe it is free to take control of CCI ports
where in practice CCI ports control is forbidden.

Add the missing CCI port availability check to the CCI driver
in order to guarantee sane CCI usage.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Liviu Dudau <liviu.dudau at arm.com>
Cc: Sudeep Holla <sudeep.holla at arm.com>
Cc: Nicolas Pitre <nicolas.pitre at linaro.org>
Cc: Suzuki K Poulose <suzuki.poulose at arm.com>
Cc: Marc Zyngier <marc.zyngier at arm.com>
---
 drivers/bus/arm-cci.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
index 5755907f..3c7a1c7 100644
--- a/drivers/bus/arm-cci.c
+++ b/drivers/bus/arm-cci.c
@@ -2199,6 +2199,9 @@ static int cci_probe_ports(struct device_node *np)
 		if (!of_match_node(arm_cci_ctrl_if_matches, cp))
 			continue;
 
+		if (!of_device_is_available(cp))
+			continue;
+
 		i = nb_ace + nb_ace_lite;
 
 		if (i >= nb_cci_ports)
@@ -2241,6 +2244,13 @@ static int cci_probe_ports(struct device_node *np)
 		ports[i].dn = cp;
 	}
 
+	/*
+	 * If there is no CCI port that is under kernel control
+	 * return early and report probe status.
+	 */
+	if (!nb_ace && !nb_ace_lite)
+		return -ENODEV;
+
 	 /* initialize a stashed array of ACE ports to speed-up look-up */
 	cci_ace_init_ports();
 
-- 
2.10.0