linux-kernel - [PATCH -next 2/2] cpuidle: RISC-V: Add ACPI LPI support

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Message-Id: <20240111093058.121838-3-sunilvl@ventanamicro.com>
Date: Thu, 11 Jan 2024 15:00:58 +0530
From: Sunil V L <sunilvl@...tanamicro.com>
To: linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-riscv@...ts.infradead.org
Cc: "Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Anup Patel <anup@...infault.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Conor Dooley <conor@...nel.org>,
	Andrew Jones <ajones@...tanamicro.com>,
	Atish Kumar Patra <atishp@...osinc.com>,
	Sunil V L <sunilvl@...tanamicro.com>
Subject: [PATCH -next 2/2] cpuidle: RISC-V: Add ACPI LPI support

Add required callbacks to support Low Power Idle (LPI) on ACPI based
RISC-V platforms.

Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
---
 drivers/cpuidle/cpuidle-riscv-sbi.c | 78 +++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
index e8094fc92491..cea67a54ab39 100644
--- a/drivers/cpuidle/cpuidle-riscv-sbi.c
+++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
@@ -632,3 +632,81 @@ static int __init sbi_cpuidle_init(void)
 	return 0;
 }
 device_initcall(sbi_cpuidle_init);
+
+#ifdef CONFIG_ACPI_PROCESSOR_IDLE
+
+#include <linux/acpi.h>
+#include <acpi/processor.h>
+
+#define RISCV_FFH_LPI_TYPE_MASK		0x1000000000000000ULL
+#define RISCV_FFH_LPI_RSVD_MASK		0x0FFFFFFF00000000ULL
+
+static int acpi_cpu_init_idle(unsigned int cpu)
+{
+	int i;
+	struct acpi_lpi_state *lpi;
+	struct acpi_processor *pr = per_cpu(processors, cpu);
+
+	if (unlikely(!pr || !pr->flags.has_lpi))
+		return -EINVAL;
+
+	/*
+	 * The SBI HSM suspend function is only available when:
+	 * 1) SBI version is 0.3 or higher
+	 * 2) SBI HSM extension is available
+	 */
+	if (sbi_spec_version < sbi_mk_version(0, 3) ||
+	    !sbi_probe_extension(SBI_EXT_HSM)) {
+		pr_warn("HSM suspend not available\n");
+		return -EINVAL;
+	}
+
+	if (pr->power.count <= 1)
+		return -ENODEV;
+
+	for (i = 1; i < pr->power.count; i++) {
+		u32 state;
+
+		lpi = &pr->power.lpi_states[i];
+
+		/* Validate Entry Method as per FFH spec.
+		 * bits[63:60] should be 0x1
+		 * bits[59:32] should be 0x0
+		 * bits[31:0] represent a SBI power_state
+		 */
+		if (!(lpi->address & RISCV_FFH_LPI_TYPE_MASK) ||
+		    (lpi->address & RISCV_FFH_LPI_RSVD_MASK)) {
+			pr_warn("Invalid LPI entry method %#llx\n", lpi->address);
+			return -EINVAL;
+		}
+
+		state = lpi->address;
+		if (!sbi_suspend_state_is_valid(state)) {
+			pr_warn("Invalid SBI power state %#x\n", state);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+int acpi_processor_ffh_lpi_probe(unsigned int cpu)
+{
+	return acpi_cpu_init_idle(cpu);
+}
+
+int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi)
+{
+	u32 state = lpi->address;
+
+	if (state & SBI_HSM_SUSP_NON_RET_BIT)
+		return CPU_PM_CPU_IDLE_ENTER_PARAM(sbi_suspend,
+						   lpi->index,
+						   state);
+	else
+		return CPU_PM_CPU_IDLE_ENTER_RETENTION_PARAM(sbi_suspend,
+							     lpi->index,
+							     state);
+}
+
+#endif
-- 
2.34.1