The SysTick is a simple 24-bit system timer that's required for ARMv7-M implementations. Add a clocksource driver for it for Cortex-M system support.
Signed-off-by: Ahmad Fatoum <[email protected]> --- drivers/clocksource/Kconfig | 5 ++ drivers/clocksource/Makefile | 1 + drivers/clocksource/armv7m_systick.c | 87 ++++++++++++++++++++++++++++ 3 files changed, 93 insertions(+) create mode 100644 drivers/clocksource/armv7m_systick.c diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig index c6ca72d4e927..9fae1f2d352e 100644 --- a/drivers/clocksource/Kconfig +++ b/drivers/clocksource/Kconfig @@ -115,4 +115,9 @@ config CLINT_TIMER This option enables the CLINT timer for RISC-V systems. The CLINT driver is usually used for NoMMU RISC-V systems. +config ARMV7M_SYSTICK + bool "Support for the ARMv7M system timer" if COMPILE_TEST + help + This option enables support for the ARMv7M system timer unit. + endmenu diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile index 21fd83a0930b..a4a7b84fae0c 100644 --- a/drivers/clocksource/Makefile +++ b/drivers/clocksource/Makefile @@ -24,3 +24,4 @@ obj-$(CONFIG_CLOCKSOURCE_TI_DM) += timer-ti-dm.o obj-$(CONFIG_CLOCKSOURCE_TI_32K) += timer-ti-32k.o obj-$(CONFIG_CLINT_TIMER) += timer-clint.o obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o +obj-$(CONFIG_ARMV7M_SYSTICK) += armv7m_systick.o diff --git a/drivers/clocksource/armv7m_systick.c b/drivers/clocksource/armv7m_systick.c new file mode 100644 index 000000000000..5f9222c50b8a --- /dev/null +++ b/drivers/clocksource/armv7m_systick.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) Maxime Coquelin 2015 + * Author: Maxime Coquelin <[email protected]> + */ + +#include <common.h> +#include <init.h> +#include <clock.h> +#include <io.h> +#include <linux/clk.h> +#include <linux/err.h> + +#define SYST_CSR 0x00 +#define SYST_RVR 0x04 +#define SYST_CVR 0x08 +#define SYST_CALIB 0x0c + +#define SYSTICK_CTRL_EN BIT(0) +/* Clock source: 0 = Ref clock, 1 = CPU clock */ +#define SYSTICK_CTRL_CPU_CLK BIT(2) +#define SYSTICK_CAL_NOREF BIT(31) + +#define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF + +static __iomem void *systick_base; + +static u64 armv7m_systick_clocksource_read(void) +{ + return SYSTICK_LOAD_RELOAD_MASK - readl(systick_base + SYST_CVR); +} + +static struct clocksource cs = { + .read = armv7m_systick_clocksource_read, + .mask = CLOCKSOURCE_MASK(24), + .shift = 0, +}; + +static int armv7m_systick_probe(struct device_d *dev) +{ + struct clk *clk = NULL; + u32 rate, cal; + int ret; + + systick_base = dev_request_mem_region_err_null(dev, 0); + if (!systick_base) + return -ENOENT; + + ret = of_property_read_u32(dev->device_node, "clock-frequency", &rate); + if (ret) { + clk = clk_get(dev, NULL); + if (IS_ERR(clk)) + return PTR_ERR(clk); + + ret = clk_enable(clk); + if (ret) + return ret; + + rate = clk_get_rate(clk); + if (!rate) + return -EINVAL; + } + + writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, systick_base + SYST_RVR); + + cal = readl(&systick_base + SYST_CALIB); + if (cal & SYSTICK_CAL_NOREF) + writel(SYSTICK_CTRL_EN | SYSTICK_CTRL_CPU_CLK, systick_base + SYST_CSR); + else + writel(SYSTICK_CTRL_EN, systick_base + SYST_CSR); + + cs.mult = clocksource_hz2mult(rate, cs.shift); + + return init_clock(&cs); +} + +static struct of_device_id armv7m_systick_dt_ids[] = { + { .compatible = "arm,armv7m-systick", }, + { } +}; + +static struct driver_d armv7m_systick_driver = { + .name = "armv7m-systick-timer", + .probe = armv7m_systick_probe, + .of_compatible = DRV_OF_COMPAT(armv7m_systick_dt_ids), +}; +postcore_platform_driver(armv7m_systick_driver); -- 2.30.2 _______________________________________________ barebox mailing list [email protected] http://lists.infradead.org/mailman/listinfo/barebox
