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 <sean...@gmail.com>
Reviewed-by: Simon Glass <s...@chromium.org>
---

Changes in v5:
- Reorder includes (simple pm)

Changes in v4:
- Split the bus off into its own driver
- Add test
- Fix line spacing in Kconfig
- Lint

Changes in v3:
- New

 arch/sandbox/dts/test.dts                     |  6 ++
 arch/sandbox/include/asm/clk.h                |  1 +
 configs/sandbox_defconfig                     |  1 +
 .../bus/simple-pm-bus.txt                     | 44 +++++++++++++++
 drivers/core/Kconfig                          |  7 +++
 drivers/core/Makefile                         |  1 +
 drivers/core/simple-pm-bus.c                  | 56 +++++++++++++++++++
 test/dm/Makefile                              |  1 +
 test/dm/simple-pm-bus.c                       | 45 +++++++++++++++
 9 files changed, 162 insertions(+)
 create mode 100644 doc/device-tree-bindings/bus/simple-pm-bus.txt
 create mode 100644 drivers/core/simple-pm-bus.c
 create mode 100644 test/dm/simple-pm-bus.c

diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 4a277934a7..96e0b55eed 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -934,6 +934,12 @@
        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"
diff --git a/arch/sandbox/include/asm/clk.h b/arch/sandbox/include/asm/clk.h
index 1573e4a134..c184c4bffc 100644
--- a/arch/sandbox/include/asm/clk.h
+++ b/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,
 };
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index f96891ecae..ef49cd2b83 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -90,6 +90,7 @@ 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
diff --git a/doc/device-tree-bindings/bus/simple-pm-bus.txt 
b/doc/device-tree-bindings/bus/simple-pm-bus.txt
new file mode 100644
index 0000000000..6f15037131
--- /dev/null
+++ b/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>;
+       };
diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig
index 3b95b5387b..0cd687526e 100644
--- a/drivers/core/Kconfig
+++ b/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
diff --git a/drivers/core/Makefile b/drivers/core/Makefile
index bce7467da1..284af7caaa 100644
--- a/drivers/core/Makefile
+++ b/drivers/core/Makefile
@@ -6,6 +6,7 @@ obj-y   += device.o fdtaddr.o lists.o root.o uclass.o util.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_$(SPL_TPL_)SYSCON)        += syscon-uclass.o
diff --git a/drivers/core/simple-pm-bus.c b/drivers/core/simple-pm-bus.c
new file mode 100644
index 0000000000..2313bd9a27
--- /dev/null
+++ b/drivers/core/simple-pm-bus.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Sean Anderson <sean...@gmail.com>
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+
+/*
+ * Power domains are taken care of by driver_probe, so we just have to enable
+ * clocks
+ */
+static const int simple_pm_bus_probe(struct udevice *dev)
+{
+       int ret;
+       struct clk_bulk *bulk = dev_get_priv(dev);
+
+       ret = clk_get_bulk(dev, bulk);
+       if (ret)
+               return ret;
+
+       ret = clk_enable_bulk(bulk);
+       if (ret && ret != -ENOSYS && ret != -ENOTSUPP) {
+               clk_release_bulk(bulk);
+               return ret;
+       }
+       return 0;
+}
+
+static const int simple_pm_bus_remove(struct udevice *dev)
+{
+       int ret;
+       struct clk_bulk *bulk = dev_get_priv(dev);
+
+       ret = clk_release_bulk(bulk);
+       if (ret && ret != -ENOSYS && ret != -ENOTSUPP)
+               return ret;
+       else
+               return 0;
+}
+
+static const struct udevice_id simple_pm_bus_ids[] = {
+       { .compatible = "simple-pm-bus" },
+       { }
+};
+
+U_BOOT_DRIVER(simple_pm_bus_drv) = {
+       .name   = "simple_pm_bus",
+       .id     = UCLASS_SIMPLE_BUS,
+       .of_match = simple_pm_bus_ids,
+       .probe = simple_pm_bus_probe,
+       .remove = simple_pm_bus_remove,
+       .priv_auto_alloc_size = sizeof(struct clk_bulk),
+       .flags  = DM_FLAG_PRE_RELOC,
+};
diff --git a/test/dm/Makefile b/test/dm/Makefile
index ef6065b60f..e0be0d684f 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -71,4 +71,5 @@ obj-$(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
diff --git a/test/dm/simple-pm-bus.c b/test/dm/simple-pm-bus.c
new file mode 100644
index 0000000000..978c7f191e
--- /dev/null
+++ b/test/dm/simple-pm-bus.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Sean Anderson <sean...@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);
-- 
2.25.1

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