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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Sudeep Holla <sudeep.holla@arm.com>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Aaro Koskinen <aaro.koskinen@nokia.com>,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Michal Simek <michal.simek@xilinx.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Ulf Hansson <ulf.hansson@linaro.org>
Subject: Re: [PATCH v3] firmware/psci: add support for SYSTEM_RESET2
Date:   Fri, 12 Apr 2019 12:10:45 +0200
Message-ID: <2000694.m04KBuNrDd@kreacher>
In-Reply-To: <20190412100227.15024-1-sudeep.holla@arm.com>
References: <20190412100227.15024-1-sudeep.holla@arm.com>
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On Friday, April 12, 2019 12:02:27 PM CEST Sudeep Holla wrote:
> PSCI v1.1 introduced SYSTEM_RESET2 to allow both architectural resets
> where the semantics are described by the PSCI specification itself as
> well as vendor-specific resets. Currently only system warm reset
> semantics is defined as part of architectural resets by the specification.
> 
> This patch implements support for SYSTEM_RESET2 by making using of
> reboot_mode passed by the reboot infrastructure in the kernel.
> 
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/firmware/psci.c   | 24 +++++++++++++++++++++++-
>  include/uapi/linux/psci.h |  2 ++
>  2 files changed, 25 insertions(+), 1 deletion(-)
> 
> v2->v3:
> 	- Added else condition so that if SYSTEM_RESET2 fails, it ends
> 	  up doing a system halt
> 	- Wrap single statement if..else with braces because of presence
> 	  of multiple line comment
> 
> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> index c80ec1d03274..c9ea8f38bd42 100644
> --- a/drivers/firmware/psci.c
> +++ b/drivers/firmware/psci.c
> @@ -88,6 +88,7 @@ static u32 psci_function_id[PSCI_FN_MAX];
>  				PSCI_1_0_EXT_POWER_STATE_TYPE_MASK)
> 
>  static u32 psci_cpu_suspend_feature;
> +static bool psci_system_reset2_supported;
> 
>  static inline bool psci_has_ext_power_state(void)
>  {
> @@ -253,7 +254,17 @@ static int get_set_conduit_method(struct device_node
> *np)
> 
>  static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
>  {
> -	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
> +	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> +	    psci_system_reset2_supported) {
> +		/*
> +		 * reset_type[31] = 0 (architectural)
> +		 * reset_type[30:0] = 0 (SYSTEM_WARM_RESET)
> +		 * cookie = 0 (ignored by the implementation)
> +		 */
> +		invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), 0, 0, 0);
> +	} else {
> +		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
> +	}
>  }
> 
>  static void psci_sys_poweroff(void)
> @@ -451,6 +462,16 @@ static const struct platform_suspend_ops
> psci_suspend_ops = { .enter          = psci_system_suspend_enter,
>  };
> 
> +static void __init psci_init_system_reset2(void)
> +{
> +	int ret;
> +
> +	ret = psci_features(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2));
> +
> +	if (ret != PSCI_RET_NOT_SUPPORTED)
> +		psci_system_reset2_supported = true;
> +}
> +
>  static void __init psci_init_system_suspend(void)
>  {
>  	int ret;
> @@ -588,6 +609,7 @@ static int __init psci_probe(void)
>  		psci_init_smccc();
>  		psci_init_cpu_suspend();
>  		psci_init_system_suspend();
> +		psci_init_system_reset2();
>  	}
> 
>  	return 0;
> diff --git a/include/uapi/linux/psci.h b/include/uapi/linux/psci.h
> index b3bcabe380da..5b0ba0062541 100644
> --- a/include/uapi/linux/psci.h
> +++ b/include/uapi/linux/psci.h
> @@ -49,8 +49,10 @@
> 
>  #define PSCI_1_0_FN_PSCI_FEATURES		PSCI_0_2_FN(10)
>  #define PSCI_1_0_FN_SYSTEM_SUSPEND		PSCI_0_2_FN(14)
> +#define PSCI_1_1_FN_SYSTEM_RESET2		PSCI_0_2_FN(18)
> 
>  #define PSCI_1_0_FN64_SYSTEM_SUSPEND		PSCI_0_2_FN64(14)
> +#define PSCI_1_1_FN64_SYSTEM_RESET2		PSCI_0_2_FN64(18)
> 
>  /* PSCI v0.2 power state encoding for CPU_SUSPEND function */
>  #define PSCI_0_2_POWER_STATE_ID_MASK		0xffff
> --

So I queued up the PSCI series from Ulf which clashes with this patch.

I can take this one too, but I'd rather avoid becoming a PSCI maintainer as a 
result. :-)