[PATCH 2/8] soc: ti: add initial PRM driver with reset control support

[Tero Kristo <t-kristo@ti.com>]

Add initial PRM (Power and Reset Management) driver for TI OMAP class
SoCs. Initially this driver only supports reset control, but can be
extended to support rest of the functionality, like powerdomain
control, PRCM irq support etc.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
---
 arch/arm/mach-omap2/Kconfig |   1 +
 drivers/soc/ti/Makefile     |   1 +
 drivers/soc/ti/omap_prm.c   | 216 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 218 insertions(+)
 create mode 100644 drivers/soc/ti/omap_prm.c

diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
index fdb6743..42ad063 100644
--- a/arch/arm/mach-omap2/Kconfig
+++ b/arch/arm/mach-omap2/Kconfig
@@ -109,6 +109,7 @@ config ARCH_OMAP2PLUS
 	select TI_SYSC
 	select OMAP_IRQCHIP
 	select CLKSRC_TI_32K
+	select RESET_CONTROLLER
 	help
 	  Systems based on OMAP2, OMAP3, OMAP4 or OMAP5
 
diff --git a/drivers/soc/ti/Makefile b/drivers/soc/ti/Makefile
index b3868d3..788b5cd 100644
--- a/drivers/soc/ti/Makefile
+++ b/drivers/soc/ti/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_KEYSTONE_NAVIGATOR_QMSS)	+= knav_qmss.o
 knav_qmss-y := knav_qmss_queue.o knav_qmss_acc.o
 obj-$(CONFIG_KEYSTONE_NAVIGATOR_DMA)	+= knav_dma.o
 obj-$(CONFIG_AMX3_PM)			+= pm33xx.o
+obj-$(CONFIG_ARCH_OMAP2PLUS)		+= omap_prm.o
 obj-$(CONFIG_WKUP_M3_IPC)		+= wkup_m3_ipc.o
 obj-$(CONFIG_TI_SCI_PM_DOMAINS)		+= ti_sci_pm_domains.o
 obj-$(CONFIG_TI_SCI_INTA_MSI_DOMAIN)	+= ti_sci_inta_msi.o
diff --git a/drivers/soc/ti/omap_prm.c b/drivers/soc/ti/omap_prm.c
new file mode 100644
index 0000000..7c89eb8
--- /dev/null
+++ b/drivers/soc/ti/omap_prm.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * OMAP2+ PRM driver
+ *
+ * Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/
+ *	Tero Kristo <t-kristo@ti.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/delay.h>
+
+struct omap_rst_map {
+	s8 rst;
+	s8 st;
+};
+
+struct omap_prm_data {
+	u32 base;
+	const char *name;
+	u16 pwstctrl;
+	u16 pwstst;
+	u16 rstctl;
+	u16 rstst;
+	struct omap_rst_map *rstmap;
+	u8 flags;
+};
+
+struct omap_prm {
+	const struct omap_prm_data *data;
+	void __iomem *base;
+};
+
+struct omap_reset_data {
+	struct reset_controller_dev rcdev;
+	struct omap_prm *prm;
+};
+
+#define to_omap_reset_data(p) container_of((p), struct omap_reset_data, rcdev)
+
+#define OMAP_MAX_RESETS		8
+#define OMAP_RESET_MAX_WAIT	10000
+
+#define OMAP_PRM_NO_RSTST	BIT(0)
+
+static const struct of_device_id omap_prm_id_table[] = {
+	{ },
+};
+
+static int omap_reset_status(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct omap_reset_data *reset = to_omap_reset_data(rcdev);
+	u32 v;
+
+	v = readl_relaxed(reset->prm->base + reset->prm->data->rstst);
+	v &= 1 << id;
+	v >>= id;
+
+	return v;
+}
+
+static int omap_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct omap_reset_data *reset = to_omap_reset_data(rcdev);
+	u32 v;
+
+	/* assert the reset control line */
+	v = readl_relaxed(reset->prm->base + reset->prm->data->rstctl);
+	v |= 1 << id;
+	writel_relaxed(v, reset->prm->base + reset->prm->data->rstctl);
+
+	return 0;
+}
+
+static int omap_reset_get_st_bit(struct omap_reset_data *reset,
+				 unsigned long id)
+{
+	struct omap_rst_map *map = reset->prm->data->rstmap;
+
+	while (map && map->rst >= 0) {
+		if (map->rst == id)
+			return map->st;
+
+		map++;
+	}
+
+	return id;
+}
+
+/*
+ * Note that status will not change until clocks are on, and clocks cannot be
+ * enabled until reset is deasserted. Consumer drivers must check status
+ * separately after enabling clocks.
+ */
+static int omap_reset_deassert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	struct omap_reset_data *reset = to_omap_reset_data(rcdev);
+	u32 v;
+	int st_bit = id;
+	bool has_rstst;
+
+	/* check the current status to avoid de-asserting the line twice */
+	v = readl_relaxed(reset->prm->base + reset->prm->data->rstctl);
+	if (!(v & BIT(id)))
+		return -EEXIST;
+
+	has_rstst = !(reset->prm->data->flags & OMAP_PRM_NO_RSTST);
+
+	if (has_rstst) {
+		st_bit = omap_reset_get_st_bit(reset, id);
+
+		/* Clear the reset status by writing 1 to the status bit */
+		v = readl_relaxed(reset->prm->base + reset->prm->data->rstst);
+		v |= 1 << st_bit;
+		writel_relaxed(v, reset->prm->base + reset->prm->data->rstst);
+	}
+
+	/* de-assert the reset control line */
+	v = readl_relaxed(reset->prm->base + reset->prm->data->rstctl);
+	v &= ~(1 << id);
+	writel_relaxed(v, reset->prm->base + reset->prm->data->rstctl);
+
+	return 0;
+}
+
+static const struct reset_control_ops omap_reset_ops = {
+	.assert		= omap_reset_assert,
+	.deassert	= omap_reset_deassert,
+	.status		= omap_reset_status,
+};
+
+static int omap_prm_reset_probe(struct platform_device *pdev,
+				struct omap_prm *prm)
+{
+	struct omap_reset_data *reset;
+
+	/*
+	 * Check if we have resets. If either rstctl or rstst is
+	 * non-zero, we have reset registers in place. Additionally
+	 * the flag OMAP_PRM_NO_RSTST implies that we have resets.
+	 */
+	if (!prm->data->rstctl && !prm->data->rstst &&
+	    !(prm->data->flags & OMAP_PRM_NO_RSTST))
+		return 0;
+
+	reset = devm_kzalloc(&pdev->dev, sizeof(*reset), GFP_KERNEL);
+	if (!reset)
+		return -ENOMEM;
+
+	reset->rcdev.owner = THIS_MODULE;
+	reset->rcdev.ops = &omap_reset_ops;
+	reset->rcdev.of_node = pdev->dev.of_node;
+	reset->rcdev.nr_resets = OMAP_MAX_RESETS;
+
+	reset->prm = prm;
+
+	return devm_reset_controller_register(&pdev->dev, &reset->rcdev);
+}
+
+static int omap_prm_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	const struct omap_prm_data *data;
+	struct omap_prm *prm;
+	const struct of_device_id *match;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	match = of_match_device(omap_prm_id_table, &pdev->dev);
+	if (!match)
+		return -ENOTSUPP;
+
+	prm = devm_kzalloc(&pdev->dev, sizeof(*prm), GFP_KERNEL);
+	if (!prm)
+		return -ENOMEM;
+
+	data = match->data;
+
+	while (data->base != res->start) {
+		if (!data->base)
+			return -EINVAL;
+		data++;
+	}
+
+	prm->data = data;
+
+	prm->base = devm_ioremap_resource(&pdev->dev, res);
+	if (!prm->base)
+		return -ENOMEM;
+
+	return omap_prm_reset_probe(pdev, prm);
+}
+
+static struct platform_driver omap_prm_driver = {
+	.probe = omap_prm_probe,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= omap_prm_id_table,
+	},
+};
+builtin_platform_driver(omap_prm_driver);
+
+MODULE_ALIAS("platform:prm");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("omap2+ prm driver");
-- 
1.9.1

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