Re: [PATCH 3/3] firmware/psci: Allow specifying an S2RAM state through CPU_SUSPEND

Lorenzo Pieralisi
2024-11-13T12:57:29Z

On Mon, Oct 28, 2024 at 03:22:59PM +0100, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>
> Certain firmware implementations (such as the ones found on Qualcomm
> SoCs between roughly 2015 and 2023) expose an S3-like S2RAM state
> through the CPU_SUSPEND call.
>
> This works exactly like SYSTEM_SUSPEND. The PSCI spec describes that
> call as optional (and only introduced in PSCIv1.0), so not all
> platforms expose it.
>
> Marking a DT-described "domain-idle-state" as such isn't currently
> well accounted for in the PSCI idle topology infrastructure: the
> cpuidle and genpd framework are deeply intertwined, and trying to
> separate them would cause more havoc than good.

I don't understand what you mean here please elaborate.

The part of the story I understand is that you have a system (well,
firmware for an extended set of systems) that does not implement
SYSTEM_SUSPEND but can reach a S2R like system state through the
CPU_SUSPEND call. Firmware works in OS-initiated mode, idle-states
should allow you to define idle states that allow the system to
enter the S2R state through CPUidle.

Please explain to me what's missing.

> Instead, allow the specifying of a single CPU_SUSPEND sleep param
> under the /psci node that shall be treated exactly like SYSTEM_SUSPEND
> from Linux's POV. As a bonus, this way we also don't have to fight
> with the genpd idle governor to avoid taking the S3-like state into
> consideration.

That's not acceptable. I want to understand what's preventing this
system to enter that state through suspend2idle and the mainline code.

> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> ---
> drivers/firmware/psci/psci.c | 36 +++++++++++++++++++++++++++++++-----
> 1 file changed, 31 insertions(+), 5 deletions(-)

NACK

> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 0e622aa5ad58bbe69dfc3a71bced597618e73f15..20ae6a6d59a9f276db75260b6ca1a5827e443782 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -78,6 +78,7 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
>
> static u32 psci_cpu_suspend_feature;
> static bool psci_system_reset2_supported;
> +static u32 psci_s2ram_suspend_param;
>
> static inline bool psci_has_ext_power_state(void)
> {
> @@ -519,10 +520,10 @@ static int psci_system_suspend_begin(suspend_state_t state)
> return 0;
> }
>
> -static const struct platform_suspend_ops psci_suspend_ops = {
> - .valid = suspend_valid_only_mem,
> - .enter = psci_system_suspend_enter,
> - .begin = psci_system_suspend_begin,
> +static const struct platform_suspend_ops psci_system_suspend_ops = {
> + .valid = suspend_valid_only_mem,
> + .enter = psci_system_suspend_enter,
> + .begin = psci_system_suspend_begin,
> };
>
> static void __init psci_init_system_reset2(void)
> @@ -545,7 +546,7 @@ static void __init psci_init_system_suspend(void)
> ret = psci_features(PSCI_FN_NATIVE(1_0, SYSTEM_SUSPEND));
>
> if (ret != PSCI_RET_NOT_SUPPORTED)
> - suspend_set_ops(&psci_suspend_ops);
> + suspend_set_ops(&psci_system_suspend_ops);
> }
>
> static void __init psci_init_cpu_suspend(void)
> @@ -673,6 +674,17 @@ static int __init psci_probe(void)
>
> typedef int (*psci_initcall_t)(const struct device_node *);
>
> +static int psci_cpu_suspend_s2ram_enter(suspend_state_t state)
> +{
> + return psci_cpu_suspend_enter(psci_s2ram_suspend_param);
> +}
> +
> +static const struct platform_suspend_ops psci_cpu_suspend_s2ram_ops = {
> + .valid = suspend_valid_only_mem,
> + .enter = psci_cpu_suspend_s2ram_enter,
> + .begin = psci_system_suspend_begin,
> +};
> +
> /*
> * PSCI init function for PSCI versions >=0.2
> *
> @@ -686,6 +698,20 @@ static int __init psci_0_2_init(const struct device_node *np)
> if (err)
> return err;
>
> + /*
> + * Some firmwares expose S2RAM entry through a custom suspend param.
> + *
> + * If found, register a suspend handler instead of registering the
> + * idle state with cpuidle.
> + */
> + err = of_property_read_u32(np, "arm,psci-s2ram-param", &psci_s2ram_suspend_param);
> + if (!err) {
> + suspend_set_ops(&psci_cpu_suspend_s2ram_ops);
> + } else if (err != -EINVAL) {
> + pr_err("Couldn't read the S2RAM PSCI suspend param: %d\n",
> + psci_s2ram_suspend_param);
> + }
> +
> /*
> * Starting with v0.2, the PSCI specification introduced a call
> * (PSCI_VERSION) that allows probing the firmware version, so
>
> --
> 2.47.0
>