dm: Add support for simple-pm-bus

This type of bus is used in Linux to designate buses which have power
domains and/or clocks which need to be enabled before their child devices
can be used. Because power domains are automatically enabled before probing
in U-Boot, we just need to enable any clocks present.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/dts/test.dts

@@ -1038,6 +1038,12 @@
 	mdio: mdio-test {
 		compatible = "sandbox,mdio";
 	};
+
+	pm-bus-test {
+		compatible = "simple-pm-bus";
+		clocks = <&clk_sandbox 4>;
+		power-domains = <&pwrdom 1>;
+	};
 };
 
 #include "sandbox_pmic.dtsi"

arch/sandbox/include/asm/clk.h

@@ -21,6 +21,7 @@ enum sandbox_clk_id {
 	SANDBOX_CLK_ID_I2C,
 	SANDBOX_CLK_ID_UART1,
 	SANDBOX_CLK_ID_UART2,
+	SANDBOX_CLK_ID_BUS,
 
 	SANDBOX_CLK_ID_COUNT,
 };

configs/sandbox_defconfig

@@ -96,6 +96,7 @@ CONFIG_REGMAP=y
 CONFIG_SYSCON=y
 CONFIG_DEVRES=y
 CONFIG_DEBUG_DEVRES=y
+CONFIG_SIMPLE_PM_BUS=y
 CONFIG_ADC=y
 CONFIG_ADC_SANDBOX=y
 CONFIG_AXI=y

doc/device-tree-bindings/bus/simple-pm-bus.txt

@@ -0,0 +1,44 @@
+Simple Power-Managed Bus
+========================
+
+A Simple Power-Managed Bus is a transparent bus that doesn't need a real
+driver, as it's typically initialized by the boot loader.
+
+However, its bus controller is part of a PM domain, or under the control of a
+functional clock.  Hence, the bus controller's PM domain and/or clock must be
+enabled for child devices connected to the bus (either on-SoC or externally)
+to function.
+
+While "simple-pm-bus" follows the "simple-bus" set of properties, as specified
+in the Devicetree Specification, it is not an extension of "simple-bus".
+
+
+Required properties:
+  - compatible: Must contain at least "simple-pm-bus".
+		Must not contain "simple-bus".
+		It's recommended to let this be preceded by one or more
+		vendor-specific compatible values.
+  - #address-cells, #size-cells, ranges: Must describe the mapping between
+		parent address and child address spaces.
+
+Optional platform-specific properties for clock or PM domain control (at least
+one of them is required):
+  - clocks: Must contain a reference to the functional clock(s),
+  - power-domains: Must contain a reference to the PM domain.
+Please refer to the binding documentation for the clock and/or PM domain
+providers for more details.
+
+
+Example:
+
+	bsc: bus@fec10000 {
+		compatible = "renesas,bsc-sh73a0", "renesas,bsc",
+			     "simple-pm-bus";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges = <0 0 0x20000000>;
+		reg = <0xfec10000 0x400>;
+		interrupts = <0 39 IRQ_TYPE_LEVEL_HIGH>;
+		clocks = <&zb_clk>;
+		power-domains = <&pd_a4s>;
+	};

drivers/core/Kconfig

@@ -195,6 +195,13 @@ config SPL_SIMPLE_BUS
 	  Supports the 'simple-bus' driver, which is used on some systems
 	  in SPL.
 
+config SIMPLE_PM_BUS
+	bool "Support simple-pm-bus driver"
+	depends on DM && OF_CONTROL && CLK && POWER_DOMAIN
+	help
+	  Supports the 'simple-pm-bus' driver, which is used for busses that
+	  have power domains and/or clocks which need to be enabled before use.
+
 config OF_TRANSLATE
 	bool "Translate addresses using fdt_translate_address"
 	depends on DM && OF_CONTROL

drivers/core/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_$(SPL_TPL_)ACPIGEN) += acpi.o
 obj-$(CONFIG_DEVRES) += devres.o
 obj-$(CONFIG_$(SPL_)DM_DEVICE_REMOVE)	+= device-remove.o
 obj-$(CONFIG_$(SPL_)SIMPLE_BUS)	+= simple-bus.o
+obj-$(CONFIG_SIMPLE_PM_BUS)	+= simple-pm-bus.o
 obj-$(CONFIG_DM)	+= dump.o
 obj-$(CONFIG_$(SPL_TPL_)REGMAP)	+= regmap.o
 obj-$(CONFIG_$(SPL_TPL_)SYSCON)	+= syscon-uclass.o

drivers/core/simple-pm-bus.c

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Sean Anderson <seanga2@gmail.com>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+
+/*
+ * Power domains are taken care of by driver_probe, so we just have to enable
+ * clocks
+ */
+static int simple_pm_bus_probe(struct udevice *dev)
+{
+	int ret;
+	struct clk_bulk *bulk = dev_get_priv(dev);
+
+	ret = clk_get_bulk(dev, bulk);
+	if (ret)
+		return ret;
+
+	ret = clk_enable_bulk(bulk);
+	if (ret && ret != -ENOSYS && ret != -ENOTSUPP) {
+		clk_release_bulk(bulk);
+		return ret;
+	}
+	return 0;
+}
+
+static int simple_pm_bus_remove(struct udevice *dev)
+{
+	int ret;
+	struct clk_bulk *bulk = dev_get_priv(dev);
+
+	ret = clk_release_bulk(bulk);
+	if (ret && ret != -ENOSYS && ret != -ENOTSUPP)
+		return ret;
+	else
+		return 0;
+}
+
+static const struct udevice_id simple_pm_bus_ids[] = {
+	{ .compatible = "simple-pm-bus" },
+	{ }
+};
+
+U_BOOT_DRIVER(simple_pm_bus_drv) = {
+	.name	= "simple_pm_bus",
+	.id	= UCLASS_SIMPLE_BUS,
+	.of_match = simple_pm_bus_ids,
+	.probe = simple_pm_bus_probe,
+	.remove = simple_pm_bus_remove,
+	.priv_auto_alloc_size = sizeof(struct clk_bulk),
+	.flags	= DM_FLAG_PRE_RELOC,
+};

test/dm/Makefile

@@ -74,4 +74,5 @@ obj-$(CONFIG_DM_MDIO) += mdio.o
 obj-$(CONFIG_DM_MDIO_MUX) += mdio_mux.o
 obj-$(CONFIG_DM_RNG) += rng.o
 obj-$(CONFIG_CLK_K210_SET_RATE) += k210_pll.o
+obj-$(CONFIG_SIMPLE_PM_BUS) += simple-pm-bus.o
 endif

test/dm/simple-pm-bus.c

@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Sean Anderson <seanga2@gmail.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/test.h>
+#include <dm/device-internal.h>
+#include <test/ut.h>
+#include <asm/clk.h>
+#include <asm/power-domain.h>
+
+/* These must match the ids in the device tree */
+#define TEST_CLOCK_ID 4
+#define TEST_POWER_ID 1
+
+static int dm_test_simple_pm_bus(struct unit_test_state *uts)
+{
+	struct udevice *power;
+	struct udevice *clock;
+	struct udevice *bus;
+
+	ut_assertok(uclass_get_device_by_name(UCLASS_POWER_DOMAIN,
+					      "power-domain", &power));
+	ut_assertok(uclass_get_device_by_name(UCLASS_CLK, "clk-sbox",
+					      &clock));
+	ut_asserteq(0, sandbox_power_domain_query(power, TEST_POWER_ID));
+	ut_asserteq(0, sandbox_clk_query_enable(clock, TEST_CLOCK_ID));
+
+	ut_assertok(uclass_get_device_by_name(UCLASS_SIMPLE_BUS, "pm-bus-test",
+					      &bus));
+	ut_asserteq(1, sandbox_power_domain_query(power, TEST_POWER_ID));
+	ut_asserteq(1, sandbox_clk_query_enable(clock, TEST_CLOCK_ID));
+
+	ut_assertok(device_remove(bus, DM_REMOVE_NORMAL));
+	/* must re-probe since device_remove also removes the power domain */
+	ut_assertok(uclass_get_device_by_name(UCLASS_POWER_DOMAIN,
+					      "power-domain", &power));
+	ut_asserteq(0, sandbox_power_domain_query(power, TEST_POWER_ID));
+	ut_asserteq(0, sandbox_clk_query_enable(clock, TEST_CLOCK_ID));
+
+	return 0;
+}
+DM_TEST(dm_test_simple_pm_bus, DM_TESTF_SCAN_FDT);