[PATCH] drivers: firmware: psci: use kernel restart handler functionality

[PATCH] drivers: firmware: psci: use kernel restart handler functionality

[Stefan Agner]

From: Stefan Agner <stefan.agner@toradex.com>

Use the kernels restart handler to register the PSCI system reset
capability. The restart handler use notifier chains along with
priorities. This allows to use restart handlers with higher priority
(in case available) while still supporting PSCI.

Since the ARM handler had priority over the kernels restart handler
before this patch, use a slightly elevated priority of 160 to make
sure PSCI is used before most of the other handlers are called.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
---
 drivers/firmware/psci/psci.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index 84f4ff351c62..d8677b54132f 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -82,6 +82,7 @@ static u32 psci_function_id[PSCI_FN_MAX];
 
 static u32 psci_cpu_suspend_feature;
 static bool psci_system_reset2_supported;
+static struct notifier_block psci_restart_handler;
 
 static inline bool psci_has_ext_power_state(void)
 {
@@ -250,7 +251,8 @@ static int get_set_conduit_method(struct device_node *np)
 	return 0;
 }
 
-static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
+static int psci_sys_reset(struct notifier_block *this,
+			    unsigned long reboot_mode, void *cmd)
 {
 	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
 	    psci_system_reset2_supported) {
@@ -263,6 +265,8 @@ static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
 	} else {
 		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
 	}
+
+	return NOTIFY_DONE;
 }
 
 static void psci_sys_poweroff(void)
@@ -411,6 +415,8 @@ static void __init psci_init_smccc(void)
 
 static void __init psci_0_2_set_functions(void)
 {
+	int ret;
+
 	pr_info("Using standard PSCI v0.2 function IDs\n");
 	psci_ops.get_version = psci_get_version;
 
@@ -431,7 +437,14 @@ static void __init psci_0_2_set_functions(void)
 
 	psci_ops.migrate_info_type = psci_migrate_info_type;
 
-	arm_pm_restart = psci_sys_reset;
+	psci_restart_handler.notifier_call = psci_sys_reset;
+	psci_restart_handler.priority = 160;
+
+	ret = register_restart_handler(&psci_restart_handler);
+	if (ret) {
+		pr_err("Cannot register restart handler, %d\n", ret);
+		return;
+	}
 
 	pm_power_off = psci_sys_poweroff;
 }
-- 
2.23.0

Re: [PATCH] drivers: firmware: psci: use kernel restart handler functionality

[Sudeep Holla]

On Sat, Oct 12, 2019 at 11:47:35PM +0200, Stefan Agner wrote:
> From: Stefan Agner <stefan.agner@toradex.com>
> 
> Use the kernels restart handler to register the PSCI system reset
> capability. The restart handler use notifier chains along with
> priorities. This allows to use restart handlers with higher priority
> (in case available) while still supporting PSCI.
> 
> Since the ARM handler had priority over the kernels restart handler
> before this patch, use a slightly elevated priority of 160 to make
> sure PSCI is used before most of the other handlers are called.
> 

There's an attempt(rather pull request[1]) to consolidate these into new
system power/restart handler.

--
Regards,
Sudeep

[1] https://lore.kernel.org/linux-arm-kernel/20191002131228.4085560-1-thierry.reding@gmail.com

Re: [PATCH] drivers: firmware: psci: use kernel restart handler functionality

[Stefan Agner]

Hi Sudeep,


On 2019-10-14 12:07, Sudeep Holla wrote:
> On Sat, Oct 12, 2019 at 11:47:35PM +0200, Stefan Agner wrote:
>> From: Stefan Agner <stefan.agner@toradex.com>
>>
>> Use the kernels restart handler to register the PSCI system reset
>> capability. The restart handler use notifier chains along with
>> priorities. This allows to use restart handlers with higher priority
>> (in case available) while still supporting PSCI.
>>
>> Since the ARM handler had priority over the kernels restart handler
>> before this patch, use a slightly elevated priority of 160 to make
>> sure PSCI is used before most of the other handlers are called.
>>
> 
> There's an attempt(rather pull request[1]) to consolidate these into new
> system power/restart handler.

Oh thanks for the pointer! Interesting timing :-)

--
Stefan

> 
> --
> Regards,
> Sudeep
> 
> [1]
> https://lore.kernel.org/linux-arm-kernel/20191002131228.4085560-1-thierry.reding@gmail.com