[v2,2/5] soc: samsung: Add USI driver

diff --git a/drivers/soc/samsung/Kconfig b/drivers/soc/samsung/Kconfig
index e2cedef1e8d1..a9f8b224322e 100644
--- a/drivers/soc/samsung/Kconfig
+++ b/drivers/soc/samsung/Kconfig
@@ -23,6 +23,20 @@  config EXYNOS_CHIPID
 	  Support for Samsung Exynos SoC ChipID and Adaptive Supply Voltage.
 	  This driver can also be built as module (exynos_chipid).
 
+config EXYNOS_USI
+	tristate "Exynos USI (Universal Serial Interface) driver"
+	default ARCH_EXYNOS && ARM64
+	depends on ARCH_EXYNOS || COMPILE_TEST
+	select MFD_SYSCON
+	help
+	  Enable support for USI block. USI (Universal Serial Interface) is an
+	  IP-core found in modern Samsung Exynos SoCs, like Exynos850 and
+	  ExynosAutoV0. USI block can be configured to provide one of the
+	  following serial protocols: UART, SPI or High Speed I2C.
+
+	  This driver allows one to configure USI for desired protocol, which
+	  is usually done in USI node in Device Tree.
+
 config EXYNOS_PMU
 	bool "Exynos PMU controller driver" if COMPILE_TEST
 	depends on ARCH_EXYNOS || ((ARM || ARM64) && COMPILE_TEST)
diff --git a/drivers/soc/samsung/Makefile b/drivers/soc/samsung/Makefile
index 2ae4bea804cf..9f59d1905ab0 100644
--- a/drivers/soc/samsung/Makefile
+++ b/drivers/soc/samsung/Makefile
@@ -4,6 +4,8 @@  obj-$(CONFIG_EXYNOS_ASV_ARM)	+= exynos5422-asv.o
 obj-$(CONFIG_EXYNOS_CHIPID)	+= exynos_chipid.o
 exynos_chipid-y			+= exynos-chipid.o exynos-asv.o
 
+obj-$(CONFIG_EXYNOS_USI)	+= exynos-usi.o
+
 obj-$(CONFIG_EXYNOS_PMU)	+= exynos-pmu.o
 
 obj-$(CONFIG_EXYNOS_PMU_ARM_DRIVERS)	+= exynos3250-pmu.o exynos4-pmu.o \
diff --git a/drivers/soc/samsung/exynos-usi.c b/drivers/soc/samsung/exynos-usi.c
new file mode 100644
index 000000000000..6e4112696f49
--- /dev/null
+++ b/drivers/soc/samsung/exynos-usi.c
@@ -0,0 +1,274 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Linaro Ltd.
+ * Author: Sam Protsenko <semen.protsenko@linaro.org>
+ *
+ * Samsung Exynos USI driver (Universal Serial Interface).
+ */
+
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+
+#include <dt-bindings/soc/samsung,exynos-usi.h>
+
+/* USIv2: System Register: SW_CONF register bits */
+#define USI_V2_SW_CONF_NONE	0x0
+#define USI_V2_SW_CONF_UART	BIT(0)
+#define USI_V2_SW_CONF_SPI	BIT(1)
+#define USI_V2_SW_CONF_I2C	BIT(2)
+#define USI_V2_SW_CONF_MASK	(USI_V2_SW_CONF_UART | USI_V2_SW_CONF_SPI | \
+				 USI_V2_SW_CONF_I2C)
+
+/* USIv2: USI register offsets */
+#define USI_CON			0x04
+#define USI_OPTION		0x08
+
+/* USIv2: USI register bits */
+#define USI_CON_RESET		BIT(0)
+#define USI_OPTION_CLKREQ_ON	BIT(1)
+#define USI_OPTION_CLKSTOP_ON	BIT(2)
+
+enum exynos_usi_ver {
+	USI_VER2 = 2,
+};
+
+struct exynos_usi_variant {
+	enum exynos_usi_ver ver;	/* USI IP-core version */
+	unsigned int sw_conf_mask;	/* SW_CONF mask for all protocols */
+	size_t min_mode;		/* first index in exynos_usi_modes[] */
+	size_t max_mode;		/* last index in exynos_usi_modes[] */
+};
+
+struct exynos_usi {
+	struct device *dev;
+	void __iomem *regs;		/* USI register map */
+	struct clk *pclk;		/* USI bus clock */
+	struct clk *ipclk;		/* USI operating clock */
+
+	size_t mode;			/* current USI SW_CONF mode index */
+	bool clkreq_on;			/* always provide clock to IP */
+
+	/* System Register */
+	struct regmap *sysreg;		/* System Register map */
+	unsigned int sw_conf;		/* SW_CONF register offset in sysreg */
+
+	const struct exynos_usi_variant *data;
+};
+
+struct exynos_usi_mode {
+	const char *name;		/* mode name */
+	unsigned int val;		/* mode register value */
+};
+
+static const struct exynos_usi_mode exynos_usi_modes[] = {
+	[USI_V2_NONE] =	{ .name = "none", .val = USI_V2_SW_CONF_NONE },
+	[USI_V2_UART] =	{ .name = "uart", .val = USI_V2_SW_CONF_UART },
+	[USI_V2_SPI] =	{ .name = "spi",  .val = USI_V2_SW_CONF_SPI },
+	[USI_V2_I2C] =	{ .name = "i2c",  .val = USI_V2_SW_CONF_I2C },
+};
+
+static const struct exynos_usi_variant exynos_usi_v2_data = {
+	.ver		= USI_VER2,
+	.sw_conf_mask	= USI_V2_SW_CONF_MASK,
+	.min_mode	= USI_V2_NONE,
+	.max_mode	= USI_V2_I2C,
+};
+
+static const struct of_device_id exynos_usi_dt_match[] = {
+	{
+		.compatible = "samsung,exynos-usi-v2",
+		.data = &exynos_usi_v2_data,
+	},
+	{ }, /* sentinel */
+};
+MODULE_DEVICE_TABLE(of, exynos_usi_dt_match);
+
+/**
+ * exynos_usi_set_sw_conf - Set USI block configuration mode
+ * @usi: USI driver object
+ * @mode: Mode index
+ *
+ * Select underlying serial protocol (UART/SPI/I2C) in USI IP-core.
+ *
+ * Return: 0 on success, or negative error code on failure.
+ */
+static int exynos_usi_set_sw_conf(struct exynos_usi *usi, size_t mode)
+{
+	unsigned int val;
+	int ret;
+
+	if (mode < usi->data->min_mode || mode > usi->data->max_mode)
+		return -EINVAL;
+
+	val = exynos_usi_modes[mode].val;
+	ret = regmap_update_bits(usi->sysreg, usi->sw_conf,
+				 usi->data->sw_conf_mask, val);
+	if (ret)
+		return ret;
+
+	usi->mode = mode;
+	dev_dbg(usi->dev, "protocol: %s\n", exynos_usi_modes[usi->mode].name);
+
+	return 0;
+}
+
+/**
+ * exynos_usi_enable - Initialize USI block
+ * @usi: USI driver object
+ *
+ * USI IP-core start state is "reset" (on startup and after CPU resume). This
+ * routine enables USI block by clearing the reset flag. It also configures
+ * HWACG behavior (needed e.g. for UART Rx). It should be performed before
+ * underlying protocol becomes functional.
+ *
+ * Return: 0 on success, or negative error code on failure.
+ */
+static int exynos_usi_enable(const struct exynos_usi *usi)
+{
+	u32 val;
+	int ret;
+
+	ret = clk_prepare_enable(usi->pclk);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(usi->ipclk);
+	if (ret)
+		goto err_pclk;
+
+	/* Enable USI block */
+	val = readl(usi->regs + USI_CON);
+	val &= ~USI_CON_RESET;
+	writel(val, usi->regs + USI_CON);
+	udelay(1);
+
+	/* Continuously provide the clock to USI IP w/o gating */
+	if (usi->clkreq_on) {
+		val = readl(usi->regs + USI_OPTION);
+		val &= ~USI_OPTION_CLKSTOP_ON;
+		val |= USI_OPTION_CLKREQ_ON;
+		writel(val, usi->regs + USI_OPTION);
+	}
+
+	clk_disable_unprepare(usi->ipclk);
+err_pclk:
+	clk_disable_unprepare(usi->pclk);
+	return ret;
+}
+
+static int exynos_usi_configure(struct exynos_usi *usi)
+{
+	int ret;
+
+	ret = exynos_usi_set_sw_conf(usi, usi->mode);
+	if (ret)
+		return ret;
+
+	if (usi->data->ver == USI_VER2)
+		return exynos_usi_enable(usi);
+
+	return 0;
+}
+
+static int exynos_usi_parse_dt(struct device_node *np, struct exynos_usi *usi)
+{
+	int ret;
+	u32 mode;
+
+	ret = of_property_read_u32(np, "samsung,mode", &mode);
+	if (ret)
+		return ret;
+	if (mode < usi->data->min_mode || mode > usi->data->max_mode)
+		return -EINVAL;
+	usi->mode = mode;
+
+	usi->sysreg = syscon_regmap_lookup_by_phandle(np, "samsung,sysreg");
+	if (IS_ERR(usi->sysreg))
+		return PTR_ERR(usi->sysreg);
+
+	ret = of_property_read_u32_index(np, "samsung,sysreg", 1,
+					 &usi->sw_conf);
+	if (ret)
+		return ret;
+
+	usi->clkreq_on = of_property_read_bool(np, "samsung,clkreq-on");
+
+	return 0;
+}
+
+static int exynos_usi_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct exynos_usi *usi;
+	int ret;
+
+	usi = devm_kzalloc(dev, sizeof(*usi), GFP_KERNEL);
+	if (!usi)
+		return -ENOMEM;
+
+	usi->dev = dev;
+	platform_set_drvdata(pdev, usi);
+
+	usi->data = of_device_get_match_data(dev);
+	if (!usi->data)
+		return -EINVAL;
+
+	ret = exynos_usi_parse_dt(np, usi);
+	if (ret)
+		return ret;
+
+	if (usi->data->ver == USI_VER2) {
+		usi->regs = devm_platform_ioremap_resource(pdev, 0);
+		if (IS_ERR(usi->regs))
+			return PTR_ERR(usi->regs);
+
+		usi->pclk = devm_clk_get(dev, "pclk");
+		if (IS_ERR(usi->pclk))
+			return PTR_ERR(usi->pclk);
+
+		usi->ipclk = devm_clk_get(dev, "ipclk");
+		if (IS_ERR(usi->ipclk))
+			return PTR_ERR(usi->ipclk);
+	}
+
+	ret = exynos_usi_configure(usi);
+	if (ret)
+		return ret;
+
+	/* Make it possible to embed protocol nodes into USI np */
+	return of_platform_populate(np, NULL, NULL, dev);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int exynos_usi_resume_noirq(struct device *dev)
+{
+	struct exynos_usi *usi = dev_get_drvdata(dev);
+
+	return exynos_usi_configure(usi);
+}
+#endif
+
+static const struct dev_pm_ops exynos_usi_pm = {
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(NULL, exynos_usi_resume_noirq)
+};
+
+static struct platform_driver exynos_usi_driver = {
+	.driver = {
+		.name		= "exynos-usi",
+		.pm		= &exynos_usi_pm,
+		.of_match_table	= exynos_usi_dt_match,
+	},
+	.probe = exynos_usi_probe,
+};
+
+module_platform_driver(exynos_usi_driver);
+
+MODULE_DESCRIPTION("Samsung USI driver");
+MODULE_AUTHOR("Sam Protsenko <semen.protsenko@linaro.org>");
+MODULE_LICENSE("GPL");