bus: ti: add minimal sysc interconnect target driver

We can handle the sysc interconnect target module in a generic way for
many TI SoCs. Initially let's just enable domain clocks before the
children are probed.

The code is loosely based on the drivers/bus/ti-sysc.c of the Linux
kernel version 5.9-rc7.
For DT binding details see:
- Documentation/devicetree/bindings/bus/ti-sysc.txt

Signed-off-by: Dario Binacchi <dariobin@libero.it>

arch/arm/Kconfig

@@ -799,6 +799,7 @@ config ARCH_OMAP2PLUS
 	select SPL_BOARD_INIT if SPL
 	select SPL_STACK_R if SPL
 	select SUPPORT_SPL
+	imply TI_SYSC if DM && OF_CONTROL
 	imply FIT
 
 config ARCH_MESON

configs/nokia_rx51_defconfig

@@ -4,6 +4,7 @@ CONFIG_ARCH_OMAP2PLUS=y
 CONFIG_SYS_TEXT_BASE=0x80008000
 CONFIG_NR_DRAM_BANKS=2
 CONFIG_TARGET_NOKIA_RX51=y
+# CONFIG_TI_SYSC is not set
 # CONFIG_FIT is not set
 CONFIG_BOOTDELAY=30
 CONFIG_AUTOBOOT_KEYED=y

drivers/bus/Kconfig

@@ -5,6 +5,13 @@
 
 menu "Bus devices"
 
+config TI_SYSC
+	bool "TI sysc interconnect target module driver"
+	depends on ARCH_OMAP2PLUS
+	help
+	  Generic driver for Texas Instruments interconnect target module
+	  found on many TI SoCs.
+
 config UNIPHIER_SYSTEM_BUS
 	bool "UniPhier System Bus driver"
 	depends on ARCH_UNIPHIER

drivers/bus/Makefile

@@ -3,4 +3,5 @@
 # Makefile for the bus drivers.
 #
 
+obj-$(CONFIG_TI_SYSC)	+= ti-sysc.o
 obj-$(CONFIG_UNIPHIER_SYSTEM_BUS) += uniphier-system-bus.o

drivers/bus/ti-sysc.c

@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Texas Instruments sysc interconnect target driver
+ *
+ * Copyright (C) 2020 Dario Binacchi <dariobin@libero.it>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+
+enum ti_sysc_clocks {
+	TI_SYSC_FCK,
+	TI_SYSC_ICK,
+	TI_SYSC_MAX_CLOCKS,
+};
+
+static const char *const clock_names[] = {"fck", "ick"};
+
+struct ti_sysc_priv {
+	int clocks_count;
+	struct clk clocks[TI_SYSC_MAX_CLOCKS];
+};
+
+static const struct udevice_id ti_sysc_ids[] = {
+	{.compatible = "ti,sysc-omap2"},
+	{.compatible = "ti,sysc-omap4"},
+	{.compatible = "ti,sysc-omap4-simple"},
+	{.compatible = "ti,sysc-omap3430-sr"},
+	{.compatible = "ti,sysc-omap3630-sr"},
+	{.compatible = "ti,sysc-omap4-sr"},
+	{.compatible = "ti,sysc-omap3-sham"},
+	{.compatible = "ti,sysc-omap-aes"},
+	{.compatible = "ti,sysc-mcasp"},
+	{.compatible = "ti,sysc-usb-host-fs"},
+	{}
+};
+
+static int ti_sysc_get_one_clock(struct udevice *dev, enum ti_sysc_clocks index)
+{
+	struct ti_sysc_priv *priv = dev_get_priv(dev);
+	const char *name;
+	int err;
+
+	switch (index) {
+	case TI_SYSC_FCK:
+		break;
+	case TI_SYSC_ICK:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	name = clock_names[index];
+
+	err = clk_get_by_name(dev, name, &priv->clocks[index]);
+	if (err) {
+		if (err == -ENODATA)
+			return 0;
+
+		dev_err(dev, "failed to get %s clock\n", name);
+		return err;
+	}
+
+	return 0;
+}
+
+static int ti_sysc_put_clocks(struct udevice *dev)
+{
+	struct ti_sysc_priv *priv = dev_get_priv(dev);
+	int err;
+
+	err = clk_release_all(priv->clocks, priv->clocks_count);
+	if (err)
+		dev_err(dev, "failed to release all clocks\n");
+
+	return err;
+}
+
+static int ti_sysc_get_clocks(struct udevice *dev)
+{
+	struct ti_sysc_priv *priv = dev_get_priv(dev);
+	int i, err;
+
+	for (i = 0; i < TI_SYSC_MAX_CLOCKS; i++) {
+		err = ti_sysc_get_one_clock(dev, i);
+		if (!err)
+			priv->clocks_count++;
+		else if (err != -ENOENT)
+			return err;
+	}
+
+	return 0;
+}
+
+static int ti_sysc_child_post_remove(struct udevice *dev)
+{
+	struct ti_sysc_priv *priv = dev_get_priv(dev->parent);
+	int i, err;
+
+	for (i = 0; i < priv->clocks_count; i++) {
+		err = clk_disable(&priv->clocks[i]);
+		if (err) {
+			dev_err(dev->parent, "failed to disable %s clock\n",
+				clock_names[i]);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+static int ti_sysc_child_pre_probe(struct udevice *dev)
+{
+	struct ti_sysc_priv *priv = dev_get_priv(dev->parent);
+	int i, err;
+
+	for (i = 0; i < priv->clocks_count; i++) {
+		err = clk_enable(&priv->clocks[i]);
+		if (err) {
+			dev_err(dev->parent, "failed to enable %s clock\n",
+				clock_names[i]);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+static int ti_sysc_remove(struct udevice *dev)
+{
+	return ti_sysc_put_clocks(dev);
+}
+
+static int ti_sysc_probe(struct udevice *dev)
+{
+	int err;
+
+	err = ti_sysc_get_clocks(dev);
+	if (err)
+		goto clocks_err;
+
+	return 0;
+
+clocks_err:
+	ti_sysc_put_clocks(dev);
+	return err;
+}
+
+UCLASS_DRIVER(ti_sysc) = {
+	.id = UCLASS_SIMPLE_BUS,
+	.name = "ti_sysc",
+	.post_bind = dm_scan_fdt_dev
+};
+
+U_BOOT_DRIVER(ti_sysc) = {
+	.name = "ti_sysc",
+	.id = UCLASS_SIMPLE_BUS,
+	.of_match = ti_sysc_ids,
+	.probe = ti_sysc_probe,
+	.remove = ti_sysc_remove,
+	.child_pre_probe = ti_sysc_child_pre_probe,
+	.child_post_remove = ti_sysc_child_post_remove,
+	.priv_auto = sizeof(struct ti_sysc_priv)
+};