linux-kernel - Re: [PATCH v2 2/3] firmware: psci: Add support for dt-supplied SYSTEM

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Message-ID: <20200225110346.GF32784@bogus>
Date:   Tue, 25 Feb 2020 11:03:46 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Elliot Berman <eberman@...eaurora.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Trilok Soni <tsoni@...eaurora.org>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        David Collins <collinsd@...eaurora.org>,
        Sudeep Holla <sudeep.holla@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] firmware: psci: Add support for dt-supplied
 SYSTEM_RESET2 type

On Mon, Feb 24, 2020 at 12:57:37PM -0800, Elliot Berman wrote:
> Some implementors of PSCI may relax the requirements of the PSCI
> architectural warm reset. In order to comply with PSCI specification, a
> different reset_type value must be used. The alternate PSCI
> SYSTEM_RESET2 may be used in all warm/soft reboot scenarios, replacing
> the architectural warm reset.
>
> Signed-off-by: Elliot Berman <eberman@...eaurora.org>
> ---
>  drivers/firmware/psci/psci.c | 22 ++++++++++++++++++----
>  include/uapi/linux/psci.h    |  2 ++
>  2 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 2937d44..8f4609c 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -90,6 +90,8 @@ static u32 psci_function_id[PSCI_FN_MAX];
>
>  static u32 psci_cpu_suspend_feature;
>  static bool psci_system_reset2_supported;
> +static u32 psci_sys_reset2_reset_param =
> +	PSCI_1_1_SYSTEM_RESET2_SYSTEM_WARM_RESET;
>
>  static inline bool psci_has_ext_power_state(void)
>  {
> @@ -272,11 +274,10 @@ static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
>  	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)

Sorry for missing this earlier, you can move this comment above if others
agree to not drop that info. I am fine with removing it too.

E
>  		 * cookie = 0 (ignored by the implementation)
>  		 */
> -		invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), 0, 0, 0);
> +		invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> +			       psci_sys_reset2_reset_param, 0, 0);
>  	} else {
>  		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
>  	}
> @@ -493,6 +494,7 @@ typedef int (*psci_initcall_t)(const struct device_node *);
>  static int __init psci_0_2_init(struct device_node *np)
>  {
>  	int err;
> +	u32 param;
>
>  	err = get_set_conduit_method(np);
>  	if (err)
> @@ -505,7 +507,19 @@ static int __init psci_0_2_init(struct device_node *np)
>  	 * can be carried out according to the specific version reported
>  	 * by firmware
>  	 */
> -	return psci_probe();
> +	err = psci_probe();
> +	if (err)
> +		return err;
> +
> +	if (psci_system_reset2_supported &&
> +	    !of_property_read_u32(np, "arm,psci-sys-reset2-param", &param)) {
> +		if ((s32)param > 0)

What is the point on signed comparison here ? You are assuming all vendor
reset also as architecture by doing so which is wrong.

> +			pr_warn("%08x is an invalid architectural reset type.\n",
> +				param);

I thought the point was to have vendor reset here. Based on the 3/3 you
see to have vendor reset bit set, you ignore that by doing signed comparison
which is wrong and even the message is wrong. Specification defines only
one architectural reset(WARM RESET) and all others need to be vendor specific.

--
Regards,
Sudeep