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

Konrad Dybcio
2024-10-28T14:23:16Z

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.

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.

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

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