linux-kernel - [PATCH] firmware: arm_scmi: Give SMC transport precedence over mailbox

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Message-Id: <20241006043317.3867421-1-florian.fainelli@broadcom.com>
Date: Sat,  5 Oct 2024 21:33:17 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: linux-arm-kernel@...ts.infread.org
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Cristian Marussi <cristian.marussi@....com>,
	devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS),
	linux-kernel@...r.kernel.org (open list),
	arm-scmi@...r.kernel.org (open list:SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE),
	linux-arm-kernel@...ts.infradead.org (moderated list:SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE),
	justin.chen@...adcom.com,
	opendmb@...il.com,
	kapil.hali@...adcom.com,
	bcm-kernel-feedback-list@...adcom.com,
	Arnd Bergmann <arnd@...db.de>
Subject: [PATCH] firmware: arm_scmi: Give SMC transport precedence over mailbox

Broadcom STB platforms have for historical reasons included both
"arm,scmi-smc" and "arm,scmi" in their SCMI Device Tree node compatible
string.

After the commit cited in the Fixes tag and with a kernel
configuration that enables both the SCMI and the Mailbox transports, we
would probe the mailbox transport, but fail to complete since we would
not have a mailbox driver available.

By keeping the SMC transport objects linked first, we can let the
platform driver, match the compatible string and probe successfully with
no adverse effects on platforms using the mailbox transport.

Fixes: b53515fa177c ("firmware: arm_scmi: Make MBOX transport a standalone driver")
Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
Change-Id: I8e348e3e0deabdc5c1d596929d7f9134793f346e
---
 drivers/firmware/arm_scmi/transports/Makefile | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/transports/Makefile b/drivers/firmware/arm_scmi/transports/Makefile
index 362a406f08e6..3ba3d3bee151 100644
--- a/drivers/firmware/arm_scmi/transports/Makefile
+++ b/drivers/firmware/arm_scmi/transports/Makefile
@@ -1,8 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0-only
-scmi_transport_mailbox-objs := mailbox.o
-obj-$(CONFIG_ARM_SCMI_TRANSPORT_MAILBOX) += scmi_transport_mailbox.o
+# Keep before scmi_transport_mailbox.o to allow precedence
+# while matching the compatible.
 scmi_transport_smc-objs := smc.o
 obj-$(CONFIG_ARM_SCMI_TRANSPORT_SMC) += scmi_transport_smc.o
+scmi_transport_mailbox-objs := mailbox.o
+obj-$(CONFIG_ARM_SCMI_TRANSPORT_MAILBOX) += scmi_transport_mailbox.o
 scmi_transport_optee-objs := optee.o
 obj-$(CONFIG_ARM_SCMI_TRANSPORT_OPTEE) += scmi_transport_optee.o
 scmi_transport_virtio-objs := virtio.o
-- 
2.34.1