[PATCH v4 3/3] firmware: qcom: scm: Support cpu power down through SCM

[Lina Iyer]

Support powering down the calling cpu, by trapping into SCM. This
termination function triggers the ARM cpu to execute WFI instruction,
causing the power controller to safely power the cpu down.

Caches may be flushed before powering down the cpu. If cache controller
is set to turn off when the cpu is powered down, then the flags argument
indicates to the secure mode to flush its cache lines before executing
WFI.The warm boot reset address for the cpu should be set before the
calling into this function for the cpu to resume.

The original code for the qcom_scm_call_atomic1() comes from a patch by
Stephen Boyd [1]. The function scm_call_atomic1() has been cherry picked
and renamed to match the convention used in this file. Since there are
no users of scm_call_atomic2(), the function is not included.

[1]. https://lkml.org/lkml/2014/8/4/765

Signed-off-by: Stephen Boyd <sboyd at codeauraro.org>
Signed-off-by: Lina Iyer <lina.iyer at linaro.org>
---
 drivers/firmware/qcom_scm.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/qcom_scm.h    |  7 +++++-
 2 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 4d8ede4..994b50f 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -311,6 +311,45 @@ out:
 	return ret;
 }
 
+#define SCM_CLASS_REGISTER	(0x2 << 8)
+#define SCM_MASK_IRQS		BIT(5)
+#define SCM_ATOMIC(svc, cmd, n) (((((svc) << 10)|((cmd) & 0x3ff)) << 12) | \
+				SCM_CLASS_REGISTER | \
+				SCM_MASK_IRQS | \
+				(n & 0xf))
+
+/**
+ * qcom_scm_call_atomic1() - Send an atomic SCM command with one argument
+ * @svc_id: service identifier
+ * @cmd_id: command identifier
+ * @arg1: first argument
+ *
+ * This shall only be used with commands that are guaranteed to be
+ * uninterruptable, atomic and SMP safe.
+ */
+static s32 qcom_scm_call_atomic1(u32 svc, u32 cmd, u32 arg1)
+{
+	int context_id;
+
+	register u32 r0 asm("r0") = SCM_ATOMIC(svc, cmd, 1);
+	register u32 r1 asm("r1") = (u32)&context_id;
+	register u32 r2 asm("r2") = arg1;
+
+	asm volatile(
+			__asmeq("%0", "r0")
+			__asmeq("%1", "r0")
+			__asmeq("%2", "r1")
+			__asmeq("%3", "r2")
+#ifdef REQUIRES_SEC
+			".arch_extension sec\n"
+#endif
+			"smc    #0      @ switch to secure world\n"
+			: "=r" (r0)
+			: "r" (r0), "r" (r1), "r" (r2)
+			: "r3");
+	return r0;
+}
+
 u32 qcom_scm_get_version(void)
 {
 	int context_id;
@@ -435,3 +474,21 @@ int qcom_scm_set_warm_boot_addr(void *entry, const cpumask_t *cpus)
 	return ret;
 }
 EXPORT_SYMBOL(qcom_scm_set_warm_boot_addr);
+
+#define QCOM_SCM_CMD_TERMINATE_PC	0x2
+#define QCOM_SCM_FLUSH_FLAG_MASK	0x3
+
+/**
+ * qcom_scm_cpu_power_down() - Power down the cpu
+ * @flags - Flags to flush cache
+ *
+ * This is an end point to power down cpu. If there was a pending interrupt,
+ * the control would return from this function, otherwise, the cpu jumps to the
+ * warm boot entry point set for this cpu upon reset.
+ */
+void qcom_scm_cpu_power_down(u32 flags)
+{
+	qcom_scm_call_atomic1(QCOM_SCM_SVC_BOOT, QCOM_SCM_CMD_TERMINATE_PC,
+			flags & QCOM_SCM_FLUSH_FLAG_MASK);
+}
+EXPORT_SYMBOL(qcom_scm_cpu_power_down);
diff --git a/include/linux/qcom_scm.h b/include/linux/qcom_scm.h
index 95ef72a..d7a974d 100644
--- a/include/linux/qcom_scm.h
+++ b/include/linux/qcom_scm.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
+/* Copyright (c) 2010-2014, The Linux Foundation. All rights reserved.
  * Copyright (C) 2015 Linaro Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
@@ -16,6 +16,11 @@
 extern int qcom_scm_set_cold_boot_addr(void *entry, const cpumask_t *cpus);
 extern int qcom_scm_set_warm_boot_addr(void *entry, const cpumask_t *cpus);
 
+#define QCOM_SCM_CPU_PWR_DOWN_L2_ON	0x0
+#define QCOM_SCM_CPU_PWR_DOWN_L2_OFF	0x1
+
+extern void qcom_scm_cpu_power_down(u32 flags);
+
 #define QCOM_SCM_VERSION(major, minor) (((major) << 16) | ((minor) & 0xFF))
 
 extern u32 qcom_scm_get_version(void);
-- 
2.1.0