linux-kernel - [PATCH 3/3] firmware/psci: Allow specifying an S2RAM state through CPU

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Message-Id: <20241028-topic-cpu_suspend_s2ram-v1-3-9fdd9a04b75c@oss.qualcomm.com>
Date: Mon, 28 Oct 2024 15:22:59 +0100
From: Konrad Dybcio <konradybcio@...nel.org>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Mark Rutland <mark.rutland@....com>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, 
 Bjorn Andersson <bjorn.andersson@....qualcomm.com>, 
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: [PATCH 3/3] firmware/psci: Allow specifying an S2RAM state through
 CPU_SUSPEND

From: Konrad Dybcio <konrad.dybcio@....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@....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