Clocks are an important feature of platforms and have become increasing complex with time. Most modern SoCs have multiple PLLs and dozens of clock dividers which distribute clocks to on-chip peripherals.
Some SoC implementations have a clock API which is private to that SoC family, e.g. Tegra and Exynos. This is useful but it would be better to have a common API that can be understood and used throughout U-Boot.
Add a simple clock API as a starting point. It supports querying and setting the rate of a clock. Each clock is a device. To reduce memory and processing overhead the concept of peripheral clocks is provided. These do not need to be explicit devices - it is possible to write a driver that can adjust the I2C clock (for example) without an explicit I2C clock device. This can dramatically reduce the number of devices (and associated overhead) in a complex SoC.
Clocks are referenced by a number, and it is expected that SoCs will define that numbering themselves via an enum.
Signed-off-by: Simon Glass sjg@chromium.org ---
Changes in v3: None Changes in v2: None
drivers/Kconfig | 2 ++ drivers/Makefile | 1 + drivers/clk/Kconfig | 19 ++++++++++++ drivers/clk/Makefile | 8 +++++ drivers/clk/clk-uclass.c | 58 +++++++++++++++++++++++++++++++++++ include/clk.h | 80 ++++++++++++++++++++++++++++++++++++++++++++++++ include/dm/uclass-id.h | 1 + scripts/Makefile.spl | 1 + 8 files changed, 170 insertions(+) create mode 100644 drivers/clk/Kconfig create mode 100644 drivers/clk/Makefile create mode 100644 drivers/clk/clk-uclass.c
diff --git a/drivers/Kconfig b/drivers/Kconfig index 7c9eefc..619d93a 100644 --- a/drivers/Kconfig +++ b/drivers/Kconfig @@ -1,5 +1,7 @@ menu "Device Drivers"
+source "drivers/clk/Kconfig" + source "drivers/core/Kconfig"
source "drivers/cpu/Kconfig" diff --git a/drivers/Makefile b/drivers/Makefile index 39b7919..9f5cec7 100644 --- a/drivers/Makefile +++ b/drivers/Makefile @@ -1,3 +1,4 @@ +obj-$(CONFIG_CLK) += clk/ obj-$(CONFIG_DM) += core/ obj-$(CONFIG_DM_DEMO) += demo/ obj-$(CONFIG_BIOSEMU) += bios_emulator/ diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig new file mode 100644 index 0000000..07eb54c --- /dev/null +++ b/drivers/clk/Kconfig @@ -0,0 +1,19 @@ +config CLK + bool "Enable clock driver support" + depends on DM + help + This allows drivers to be provided for clock generators, including + oscillators and PLLs. Devices can use a common clock API to request + a particular clock rate and check on available clocks. Clocks can + feed into other clocks in a tree structure, with multiplexers to + choose the source for each clock. + +config SPL_CLK_SUPPORT + bool "Enable clock support in SPL" + depends on CLK + help + The clock subsystem adds a small amount of overhead to the image. + If this is acceptable and you have a need to use clock drivers in + SPL, enable this option. It might provide a cleaner interface to + setting up clocks within SPL, and allows the same drivers to be + used as U-Boot proper. diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile new file mode 100644 index 0000000..b51cf23 --- /dev/null +++ b/drivers/clk/Makefile @@ -0,0 +1,8 @@ +# +# Copyright (c) 2015 Google, Inc +# Wolfgang Denk, DENX Software Engineering, wd@denx.de. +# +# SPDX-License-Identifier: GPL-2.0+ +# + +obj-$(CONFIG_CLK) += clk-uclass.o diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c new file mode 100644 index 0000000..73dfd7d --- /dev/null +++ b/drivers/clk/clk-uclass.c @@ -0,0 +1,58 @@ +/* + * Copyright (C) 2015 Google, Inc + * Written by Simon Glass sjg@chromium.org + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <common.h> +#include <clk.h> +#include <dm.h> +#include <errno.h> +#include <dm/lists.h> +#include <dm/root.h> + +ulong clk_get_rate(struct udevice *dev) +{ + struct clk_ops *ops = clk_get_ops(dev); + + if (!ops->get_rate) + return -ENOSYS; + + return ops->get_rate(dev); +} + +ulong clk_set_rate(struct udevice *dev, ulong rate) +{ + struct clk_ops *ops = clk_get_ops(dev); + + if (!ops->set_rate) + return -ENOSYS; + + return ops->set_rate(dev, rate); +} + +ulong clk_get_periph_rate(struct udevice *dev, int periph) +{ + struct clk_ops *ops = clk_get_ops(dev); + + if (!ops->get_periph_rate) + return -ENOSYS; + + return ops->get_periph_rate(dev, periph); +} + +ulong clk_set_periph_rate(struct udevice *dev, int periph, ulong rate) +{ + struct clk_ops *ops = clk_get_ops(dev); + + if (!ops->set_periph_rate) + return -ENOSYS; + + return ops->set_periph_rate(dev, periph, rate); +} + +UCLASS_DRIVER(clk) = { + .id = UCLASS_CLK, + .name = "clk", +}; diff --git a/include/clk.h b/include/clk.h index df4570c..254ad2b 100644 --- a/include/clk.h +++ b/include/clk.h @@ -1,6 +1,86 @@ +/* + * Copyright (c) 2015 Google, Inc + * Written by Simon Glass sjg@chromium.org + * + * SPDX-License-Identifier: GPL-2.0+ + */ + #ifndef _CLK_H_ #define _CLK_H_
int soc_clk_dump(void);
+struct clk_ops { + /** + * get_rate() - Get current clock rate + * + * @dev: Device to check (UCLASS_CLK) + * @return clock rate in Hz, or -ve error code + */ + ulong (*get_rate)(struct udevice *dev); + + /** + * set_rate() - Set current clock rate + * + * @dev: Device to adjust + * @rate: New clock rate in Hz + * @return new rate, or -ve error code + */ + ulong (*set_rate)(struct udevice *dev, ulong rate); + + /** + * clk_set_periph_rate() - Set clock rate for a peripheral + * + * @dev: Device to adjust (UCLASS_CLK) + * @rate: New clock rate in Hz + * @return new clock rate in Hz, or -ve error code + */ + ulong (*get_periph_rate)(struct udevice *dev, int periph); + + /** + * clk_set_periph_rate() - Set current clock rate for a peripheral + * + * @dev: Device to update (UCLASS_CLK) + * @periph: Peripheral ID to cupdate + * @return new clock rate in Hz, or -ve error code + */ + ulong (*set_periph_rate)(struct udevice *dev, int periph, ulong rate); +}; + +#define clk_get_ops(dev) ((struct clk_ops *)(dev)->driver->ops) + +/** + * clk_get_rate() - Get current clock rate + * + * @dev: Device to check (UCLASS_CLK) + * @return clock rate in Hz, or -ve error code + */ +ulong clk_get_rate(struct udevice *dev); + +/** + * set_rate() - Set current clock rate + * + * @dev: Device to adjust + * @rate: New clock rate in Hz + * @return new rate, or -ve error code + */ +ulong clk_set_rate(struct udevice *dev, ulong rate); + +/** + * clk_get_periph_rate() - Get current clock rate for a peripheral + * + * @dev: Device to check (UCLASS_CLK) + * @return clock rate in Hz, -ve error code + */ +ulong clk_get_periph_rate(struct udevice *dev, int periph); + +/** + * clk_set_periph_rate() - Set current clock rate for a peripheral + * + * @dev: Device to update (UCLASS_CLK) + * @periph: Peripheral ID to cupdate + * @return new clock rate in Hz, or -ve error code + */ +ulong clk_set_periph_rate(struct udevice *dev, int periph, ulong rate); + #endif /* _CLK_H_ */ diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h index fc486f2..72512b5 100644 --- a/include/dm/uclass-id.h +++ b/include/dm/uclass-id.h @@ -25,6 +25,7 @@ enum uclass_id { UCLASS_SIMPLE_BUS, /* bus with child devices */
/* U-Boot uclasses start here - in alphabetical order */ + UCLASS_CLK, /* Clock source, e.g. used by peripherals */ UCLASS_CPU, /* CPU, typically part of an SoC */ UCLASS_CROS_EC, /* Chrome OS EC */ UCLASS_DISPLAY_PORT, /* Display port video */ diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl index c4e83bb..9d7ac99 100644 --- a/scripts/Makefile.spl +++ b/scripts/Makefile.spl @@ -54,6 +54,7 @@ libs-$(HAVE_VENDOR_COMMON_LIB) += board/$(VENDOR)/common/ libs-$(CONFIG_SPL_FRAMEWORK) += common/spl/ libs-$(CONFIG_SPL_LIBCOMMON_SUPPORT) += common/ libs-$(CONFIG_SPL_LIBDISK_SUPPORT) += disk/ +libs-$(CONFIG_SPL_CLK_SUPPORT) += drivers/clk/ libs-$(CONFIG_SPL_DM) += drivers/core/ libs-$(CONFIG_SPL_I2C_SUPPORT) += drivers/i2c/ libs-$(CONFIG_SPL_GPIO_SUPPORT) += drivers/gpio/