[PATCH 2/2] soc: samsung: Add simple voltage coupler for Exynos5800

[Marek Szyprowski]

Add custom voltage regulator coupler for Exynos5800 SoCs, which require
coupling between "vdd_arm" and "vdd_int" regulators. This coupler ensures
that coupled regulators voltage balancing is done only when clients for
each regulator (cpufreq for "vdd_arm" and devfreq for "vdd_int") apply
their constraints, so the voltage values don't go beyond the
bootloader-selected operation point during the boot process. This also
ensures proper voltage balancing if any of those drivers is missing.

Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
 arch/arm/mach-exynos/Kconfig                  |  1 +
 drivers/soc/samsung/Kconfig                   |  3 +
 drivers/soc/samsung/Makefile                  |  1 +
 .../soc/samsung/exynos-regulator-coupler.c    | 59 +++++++++++++++++++
 4 files changed, 64 insertions(+)
 create mode 100644 drivers/soc/samsung/exynos-regulator-coupler.c

diff --git a/arch/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig
index 76838255b5fa..f185cd3d4c62 100644
--- a/arch/arm/mach-exynos/Kconfig
+++ b/arch/arm/mach-exynos/Kconfig
@@ -118,6 +118,7 @@ config SOC_EXYNOS5800
 	bool "Samsung EXYNOS5800"
 	default y
 	depends on SOC_EXYNOS5420
+	select EXYNOS_REGULATOR_COUPLER
 
 config EXYNOS_MCPM
 	bool
diff --git a/drivers/soc/samsung/Kconfig b/drivers/soc/samsung/Kconfig
index c7a2003687c7..264185664594 100644
--- a/drivers/soc/samsung/Kconfig
+++ b/drivers/soc/samsung/Kconfig
@@ -37,4 +37,7 @@ config EXYNOS_PM_DOMAINS
 	bool "Exynos PM domains" if COMPILE_TEST
 	depends on PM_GENERIC_DOMAINS || COMPILE_TEST
 
+config EXYNOS_REGULATOR_COUPLER
+	bool "Exynos SoC Regulator Coupler" if COMPILE_TEST
+	depends on ARCH_EXYNOS || COMPILE_TEST
 endif
diff --git a/drivers/soc/samsung/Makefile b/drivers/soc/samsung/Makefile
index edd1d6ea064d..ecc3a32f6406 100644
--- a/drivers/soc/samsung/Makefile
+++ b/drivers/soc/samsung/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_EXYNOS_PMU)	+= exynos-pmu.o
 obj-$(CONFIG_EXYNOS_PMU_ARM_DRIVERS)	+= exynos3250-pmu.o exynos4-pmu.o \
 					exynos5250-pmu.o exynos5420-pmu.o
 obj-$(CONFIG_EXYNOS_PM_DOMAINS) += pm_domains.o
+obj-$(CONFIG_EXYNOS_REGULATOR_COUPLER) += exynos-regulator-coupler.o
diff --git a/drivers/soc/samsung/exynos-regulator-coupler.c b/drivers/soc/samsung/exynos-regulator-coupler.c
new file mode 100644
index 000000000000..54445918bd75
--- /dev/null
+++ b/drivers/soc/samsung/exynos-regulator-coupler.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020 Samsung Electronics Co., Ltd.
+ *	      http://www.samsung.com/
+ * Author: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
+ *
+ * Samsung Exynos SoC voltage coupler
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/regulator/coupler.h>
+#include <linux/regulator/driver.h>
+
+static int exynos_coupler_balance_voltage(struct regulator_coupler *coupler,
+					  struct regulator_dev *rdev,
+					  suspend_state_t state)
+{
+	struct coupling_desc *c_desc = &rdev->coupling_desc;
+	int ret, cons_uV = 0, cons_max_uV = INT_MAX;
+	bool skip_coupled = false;
+
+	/* get coupled regulator constraints */
+	ret = regulator_check_consumers(c_desc->coupled_rdevs[1], &cons_uV,
+					&cons_max_uV, state);
+	if (ret < 0)
+		return ret;
+
+	/* skip adjusting coupled regulator if it has no constraints set yet */
+	if (cons_uV == 0)
+		skip_coupled = true;
+
+	return regulator_do_balance_voltage(rdev, state, skip_coupled);
+}
+
+static int exynos_coupler_attach(struct regulator_coupler *coupler,
+				 struct regulator_dev *rdev)
+{
+	if (strcmp(rdev_get_name(rdev), "vdd_arm") == 0 ||
+	    strcmp(rdev_get_name(rdev), "vdd_int") == 0)
+		return 0;
+
+	return -EINVAL;
+}
+
+static struct regulator_coupler exynos_coupler = {
+	.attach_regulator = exynos_coupler_attach,
+	.balance_voltage  = exynos_coupler_balance_voltage,
+};
+
+static int __init exynos_coupler_init(void)
+{
+	if (!of_machine_is_compatible("samsung,exynos5800"))
+		return 0;
+
+	return regulator_coupler_register(&exynos_coupler);
+}
+arch_initcall(exynos_coupler_init);
-- 
2.17.1