[PATCH 0/2] firmware: meson: sm: make power-off work on S4

[PATCH 0/2] firmware: meson: sm: make power-off work on S4

[christian.koever-draxl]

From: Christian Stefan Kövér-Draxl <ckoever@outlook.de>

On S4 the firmware implements PSCI SYSTEM_OFF as DDR self-refresh, and
the power key then resumes into a kernel that is gone, so the board
hangs until it is unplugged. The vendor kernel sets a firmware shutdown
flag first and takes the secondary CPUs down through PSCI; do the same,
keyed on a new amlogic,meson-s4-sm compatible.

Tested: poweroff followed by the remote's power key cold-boots the box.

Tool use (Documentation/process/generated-content.rst):
This work was done with the help of an AI coding assistant, Claude
(Anthropic), used through Claude Code over many sessions. It did a large
part of the hands-on work: it read the vendor kernel and the firmware
interfaces, probed registers on the board, drafted the code and the
changelogs, and ran the builds, checkpatch, dt_binding_check and the
tests on the hardware. I directed the work, reviewed every change and
the final patches, and take responsibility for them. There is no single
prompt to quote; the sessions were of the form "find out why X fails on
this board, fix it, test it on the box".

Tested on an Amediatech X98Q TV box (Amlogic S905W2, S4 family, 2 GiB),
vendor U-Boot and BL31/OP-TEE, Linux 7.3 plus this work.

Christian Stefan Kövér-Draxl (2):
  dt-bindings: firmware: amlogic,meson-gxbb-sm: add amlogic,meson-s4-sm
  firmware: meson: sm: make power-off work on S4

 .../firmware/amlogic,meson-gxbb-sm.yaml       |  4 +-
 drivers/firmware/meson/meson_sm.c             | 46 +++++++++++++++++++
 include/linux/firmware/meson/meson_sm.h       |  1 +
 3 files changed, 50 insertions(+), 1 deletion(-)


base-commit: 7be4bc52fd9e0e55dc9a2e0232b89427d2c4b614
-- 
2.56.0

[PATCH 1/2] dt-bindings: firmware: amlogic,meson-gxbb-sm: add amlogic,meson-s4-sm

[christian.koever-draxl]

From: Christian Stefan Kövér-Draxl <ckoever@outlook.de>

The S4 secure monitor implements the GXBB interface, but its PSCI
SYSTEM_OFF needs an extra firmware call first (a shutdown flag), so the
driver has to tell it apart. Add an S4 compatible with the GXBB one as
fallback.

Signed-off-by: Christian Stefan Kövér-Draxl <ckoever@outlook.de>
---
 .../devicetree/bindings/firmware/amlogic,meson-gxbb-sm.yaml   | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/firmware/amlogic,meson-gxbb-sm.yaml b/Documentation/devicetree/bindings/firmware/amlogic,meson-gxbb-sm.yaml
index 8f50e698760e..6ff2ddfcaf54 100644
--- a/Documentation/devicetree/bindings/firmware/amlogic,meson-gxbb-sm.yaml
+++ b/Documentation/devicetree/bindings/firmware/amlogic,meson-gxbb-sm.yaml
@@ -18,7 +18,9 @@ properties:
     oneOf:
       - const: amlogic,meson-gxbb-sm
       - items:
-          - const: amlogic,meson-gx-sm
+          - enum:
+              - amlogic,meson-gx-sm
+              - amlogic,meson-s4-sm
           - const: amlogic,meson-gxbb-sm
 
   power-controller:
-- 
2.56.0

[PATCH 2/2] firmware: meson: sm: make power-off work on S4

[christian.koever-draxl]

From: Christian Stefan Kövér-Draxl <ckoever@outlook.de>

On S4 the firmware implements PSCI SYSTEM_OFF as DDR self-refresh. A
press of the power key afterwards jumps back to the kernel resume
address, where nothing is waiting, and the board hangs until it is
unplugged.

The vendor kernel avoids this in two steps, both needed:

 - set the firmware shutdown flag (SMC 0x82000042, argument 1) right
   before SYSTEM_OFF, which makes the firmware cold-boot on the power
   key instead of resuming;
 - take the secondary CPUs down through PSCI CPU_OFF first. With them
   only parked in the kernel, the firmware wake-up path hangs as well.

Register a power-off prepare handler that stops the secondary CPUs and
a high priority power-off handler that sets the flag, for the
amlogic,meson-s4-sm compatible only.

Tested on an S905W2 board: poweroff followed by the power key
cold-boots the board.

Signed-off-by: Christian Stefan Kövér-Draxl <ckoever@outlook.de>
---
 drivers/firmware/meson/meson_sm.c       | 46 +++++++++++++++++++++++++
 include/linux/firmware/meson/meson_sm.h |  1 +
 2 files changed, 47 insertions(+)

diff --git a/drivers/firmware/meson/meson_sm.c b/drivers/firmware/meson/meson_sm.c
index ab9751a59b55..5410386603c7 100644
--- a/drivers/firmware/meson/meson_sm.c
+++ b/drivers/firmware/meson/meson_sm.c
@@ -10,6 +10,7 @@
 
 #include <linux/arm-smccc.h>
 #include <linux/bug.h>
+#include <linux/cpu.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -17,6 +18,7 @@
 #include <linux/platform_device.h>
 #include <linux/printk.h>
 #include <linux/property.h>
+#include <linux/reboot.h>
 #include <linux/types.h>
 #include <linux/sizes.h>
  #include <linux/slab.h>
@@ -48,6 +50,7 @@ static const struct meson_sm_chip gxbb_chip = {
 		CMD(SM_THERMAL_CALIB_READ,	0x82000047),
 		CMD(SM_A1_PWRC_SET,		0x82000093),
 		CMD(SM_A1_PWRC_GET,		0x82000095),
+		CMD(SM_SET_POWEROFF_FLAG,	0x82000042),
 		{ /* sentinel */ },
 	},
 };
@@ -303,6 +306,45 @@ static struct attribute *meson_sm_sysfs_attrs[] = {
 };
 ATTRIBUTE_GROUPS(meson_sm_sysfs);
 
+/*
+ * The S4 firmware implements PSCI SYSTEM_OFF as DDR self-refresh: on the
+ * power key it jumps back to the kernel instead of booting, which hangs the
+ * board. Setting the shutdown flag first makes it cold-boot instead, and the
+ * secondary CPUs must have been taken down through PSCI CPU_OFF beforehand,
+ * otherwise the wake-up path hangs as well.
+ */
+static int meson_sm_power_off_prepare(struct sys_off_data *data)
+{
+	if (freeze_secondary_cpus(0))
+		pr_warn("meson-sm: failed to stop secondary CPUs\n");
+
+	return NOTIFY_DONE;
+}
+
+static int meson_sm_power_off(struct sys_off_data *data)
+{
+	meson_sm_call(data->cb_data, SM_SET_POWEROFF_FLAG, NULL, 1, 0, 0, 0, 0);
+
+	return NOTIFY_DONE;
+}
+
+static int meson_sm_register_power_off(struct device *dev,
+				       struct meson_sm_firmware *fw)
+{
+	int ret;
+
+	ret = devm_register_sys_off_handler(dev, SYS_OFF_MODE_POWER_OFF_PREPARE,
+					    SYS_OFF_PRIO_DEFAULT,
+					    meson_sm_power_off_prepare, NULL);
+	if (ret)
+		return ret;
+
+	/* Run before the PSCI handler, which never returns */
+	return devm_register_sys_off_handler(dev, SYS_OFF_MODE_POWER_OFF,
+					     SYS_OFF_PRIO_HIGH,
+					     meson_sm_power_off, fw);
+}
+
 static const struct of_device_id meson_sm_ids[] = {
 	{ .compatible = "amlogic,meson-gxbb-sm", .data = &gxbb_chip },
 	{ /* sentinel */ },
@@ -343,6 +385,10 @@ static int __init meson_sm_probe(struct platform_device *pdev)
 	if (devm_of_platform_populate(dev))
 		goto unmap_out_base;
 
+	if (of_device_is_compatible(dev->of_node, "amlogic,meson-s4-sm") &&
+	    meson_sm_register_power_off(dev, fw))
+		dev_warn(dev, "failed to register power-off handlers\n");
+
 	pr_info("secure-monitor enabled\n");
 
 	return 0;
diff --git a/include/linux/firmware/meson/meson_sm.h b/include/linux/firmware/meson/meson_sm.h
index 3ebc2bd9a976..3f2fa160e32f 100644
--- a/include/linux/firmware/meson/meson_sm.h
+++ b/include/linux/firmware/meson/meson_sm.h
@@ -15,6 +15,7 @@ enum {
 	SM_THERMAL_CALIB_READ,
 	SM_A1_PWRC_SET,
 	SM_A1_PWRC_GET,
+	SM_SET_POWEROFF_FLAG,
 };
 
 struct meson_sm_firmware;
-- 
2.56.0

Re: [PATCH 2/2] firmware: meson: sm: make power-off work on S4

[kernel test robot]

Hi,

kernel test robot noticed the following build errors:

[auto build test ERROR on 7be4bc52fd9e0e55dc9a2e0232b89427d2c4b614]

url:    https://github.com/intel-lab-lkp/linux/commits/christian-koever-draxl-student-uibk-ac-at/dt-bindings-firmware-amlogic-meson-gxbb-sm-add-amlogic-meson-s4-sm/20261025-202143
base:   7be4bc52fd9e0e55dc9a2e0232b89427d2c4b614
patch link:    https://lore.kernel.org/r/20261025192144.208954-3-christian.koever-draxl%40student.uibk.ac.at
patch subject: [PATCH 2/2] firmware: meson: sm: make power-off work on S4
config: arm64-randconfig-1000-20261028 (https://download.01.org/0day-ci/archive/20261028/202610281810.Or8lhrj7-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261028/202610281810.Or8lhrj7-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202610281810.Or8lhrj7-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/firmware/meson/meson_sm.c: In function 'meson_sm_power_off_prepare':
>> drivers/firmware/meson/meson_sm.c:318:6: error: implicit declaration of function 'freeze_secondary_cpus'; did you mean 'thaw_secondary_cpus'? [-Werror=implicit-function-declaration]
     if (freeze_secondary_cpus(0))
         ^~~~~~~~~~~~~~~~~~~~~
         thaw_secondary_cpus
   cc1: some warnings being treated as errors


vim +318 drivers/firmware/meson/meson_sm.c

   308	
   309	/*
   310	 * The S4 firmware implements PSCI SYSTEM_OFF as DDR self-refresh: on the
   311	 * power key it jumps back to the kernel instead of booting, which hangs the
   312	 * board. Setting the shutdown flag first makes it cold-boot instead, and the
   313	 * secondary CPUs must have been taken down through PSCI CPU_OFF beforehand,
   314	 * otherwise the wake-up path hangs as well.
   315	 */
   316	static int meson_sm_power_off_prepare(struct sys_off_data *data)
   317	{
 > 318		if (freeze_secondary_cpus(0))
   319			pr_warn("meson-sm: failed to stop secondary CPUs\n");
   320	
   321		return NOTIFY_DONE;
   322	}
   323	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki