Subject: [PATCH 02/12] clocksource: sti: Provide support for the ST LPC Clocksource IP

From: [email-masked] (Daniel Lezcano)
Date: Mon, 11 May 2015 10:42:47 +0200

On 05/07/2015 03:38 PM, Lee Jones wrote:
> This IP is shared with Watchdog and RTC functionality.  Only one of
> these IPs can be used at the same time.  We use the device-driver
> model combined with a DT 'mode' property to enforce this.
>
> The ST LPC Clocksource IP can be used as the system (tick) timer.
>
> Signed-off-by: Lee Jones <[email-masked]>
> ---
>   drivers/clocksource/Kconfig         |   8 +++
>   drivers/clocksource/Makefile        |   1 +
>   drivers/clocksource/clksrc_st_lpc.c | 123 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 132 insertions(+)
>   create mode 100644 drivers/clocksource/clksrc_st_lpc.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 68161f7..ac424cf 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -250,4 +250,12 @@ config CLKSRC_PXA
>   	help
>   	  This enables OST0 support available on PXA and SA-11x0
>   	  platforms.
> +
> +config CLKSRC_ST_LPC
> +	bool
> +	depends on ARCH_STI
> +	select CLKSRC_OF if OF
> +	help
> +	  Enable this option to use the Low Power controller timer
> +	  as clocksource.
>   endmenu
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 752d5c7..e08da4d 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -51,3 +51,4 @@ obj-$(CONFIG_ARCH_INTEGRATOR_AP)	+= timer-integrator-ap.o
>   obj-$(CONFIG_CLKSRC_VERSATILE)		+= versatile.o
>   obj-$(CONFIG_CLKSRC_MIPS_GIC)		+= mips-gic-timer.o
>   obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o
> +obj-$(CONFIG_CLKSRC_ST_LPC)		+= clksrc_st_lpc.o
> diff --git a/drivers/clocksource/clksrc_st_lpc.c b/drivers/clocksource/clksrc_st_lpc.c
> new file mode 100644
> index 0000000..18a7dcd0
> --- /dev/null
> +++ b/drivers/clocksource/clksrc_st_lpc.c
> @@ -0,0 +1,123 @@
> +/*
> + * Clocksource using the Low Power Timer found in the Low Power Controller (LPC)
> + *
> + * Copyright (C) 2015 STMicroelectronics ? All Rights Reserved
> + *
> + * Author(s): Francesco Virlinzi <[email-masked]>
> + *	      Ajit Pal Singh <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clocksource.h>
> +#include <linux/init.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +
> +#include <dt-bindings/mfd/st-lpc.h>
> +
> +/* Low Power Timer */
> +#define LPC_LPT_LSB_OFF		0x400
> +#define LPC_LPT_MSB_OFF		0x404
> +#define LPC_LPT_START_OFF	0x408
> +
> +static struct st_clksrc_ddata {
> +	struct clk		*clk;
> +	void __iomem		*base;
> +} ddata;
> +
> +static void st_clksrc_reset(void)
> +{
> +	writel_relaxed(0, ddata.base + LPC_LPT_START_OFF);
> +	writel_relaxed(0, ddata.base + LPC_LPT_MSB_OFF);
> +	writel_relaxed(0, ddata.base + LPC_LPT_LSB_OFF);
> +	writel_relaxed(1, ddata.base + LPC_LPT_START_OFF);
> +}
> +
> +static int __init st_clksrc_init(void)
> +{
> +	unsigned long rate;
> +	int ret;
> +
> +	st_clksrc_reset();
> +
> +	rate = clk_get_rate(ddata.clk);
> +
> +	ret = clocksource_mmio_init(ddata.base + LPC_LPT_LSB_OFF,
> +				    "clksrc-st-lpc", rate, 300, 32,
> +				    clocksource_mmio_readl_up);
> +	if (ret) {
> +		pr_err("clksrc-st-lpc: Failed to register clocksource\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int st_clksrc_setup_clk(struct device_node *np)
> +{
> +	struct clk *clk;
> +	int ret;
> +
> +	clk = of_clk_get(np, 0);
> +	if (IS_ERR(clk)) {
> +		pr_err("clksrc-st-lpc: Failed to get LPC clock\n");
> +		ret = PTR_ERR(clk);
> +		return ret;

return PTR_ERR(clk);

so you can get rid of the 'int ret' variable.

> +	}
> +
> +	if (clk_prepare_enable(clk)) {
> +		pr_err("clksrc-st-lpc: Failed to enable LPC clock\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!clk_get_rate(clk)) {
> +		pr_err("clksrc-st-lpc: Failed to get LPC clock rate\n");
> +		clk_disable_unprepare(clk);
> +		return -EINVAL;
> +	}
> +
> +	ddata.clk = clk;
> +
> +	return 0;
> +}
> +
> +static void __init st_clksrc_of_register(struct device_node *np)
> +{
> +	int ret;
> +	uint32_t mode;
> +
> +	ret = of_property_read_u32(np, "st,lpc-mode", &mode);
> +	if (ret) {
> +		pr_err("clksrc-st-lpc: An LPC mode must be provided\n");
> +		return;
> +	}
> +
> +	/* LPC can either run as a Clocksource or in RTC or WDT mode */
> +	if (mode != ST_LPC_MODE_CLKSRC)
> +		return;

I am confused with this patch description + comment and the patch 1's 
description.

For the former, I understand the LPC could be in RTC or WDT mode and 
used as a clocksource (clksrc + rtc / clksrc + wdt), for the latter I 
understand there are three modes clocksource, rtc and watchdog (mutually 
exclusive). Could you clarify ?

> +
> +	ddata.base = of_iomap(np, 0);
> +	if (!ddata.base) {
> +		pr_err("clksrc-st-lpc: Unable to map iomem\n");
> +		return;
> +	}
> +
> +	if (st_clksrc_setup_clk(np)) {
> +		iounmap(ddata.base);
> +		return;
> +	}
> +
> +	if (st_clksrc_init()) {
> +		iounmap(ddata.base);
> +		return;
> +	}
> +
> +	pr_info("clksrc-st-lpc: clocksource initialised - running @ %luHz\n",
> +		clk_get_rate(ddata.clk));
> +}
> +CLOCKSOURCE_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);
>

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