Date:   Tue, 14 May 2019 21:55:09 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Lechner <david@...hnology.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [RFC 1/2] clocksource: davinci-timer: add support for clockevents

On 17/04/2019 16:47, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> Currently the clocksource and clockevent support for davinci platforms
> lives in mach-davinci. It hard-codes many things, uses global variables,
> implements functionalities unused by any platform and has code fragments
> scattered across many (often unrelated) files.
> 
> Implement a new, modern and simplified timer driver and put it into
> drivers/clocksource. We still need to support legacy board files so
> export a config structure and a function that allows machine code to
> register the timer.
> 
> The timer we're using is 64-bit but can be programmed in dual 32-bit
> mode (both chained and unchained). We're using dual 32-bit mode to
> have separate counters for clockevents and clocksource.
> 
> This patch contains the core code and support for clockevent. The
> clocksource code will be included in a subsequent patch.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>  drivers/clocksource/Kconfig         |   5 +
>  drivers/clocksource/Makefile        |   1 +
>  drivers/clocksource/timer-davinci.c | 272 ++++++++++++++++++++++++++++
>  include/clocksource/timer-davinci.h |  44 +++++
>  4 files changed, 322 insertions(+)
>  create mode 100644 drivers/clocksource/timer-davinci.c
>  create mode 100644 include/clocksource/timer-davinci.h
> 
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 171502a356aa..974f9b50ebf4 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -42,6 +42,11 @@ config BCM_KONA_TIMER
>  	help
>  	  Enables the support for the BCM Kona mobile timer driver.
>  
> +config DAVINCI_TIMER
> +	bool "Texas Instruments DaVinci timer driver" if COMPILE_TEST
> +	help
> +	  Enables the support for the TI DaVinci timer driver.
> +
>  config DIGICOLOR_TIMER
>  	bool "Digicolor timer driver" if COMPILE_TEST
>  	select CLKSRC_MMIO
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index be6e0fbc7489..3c73d0e58b45 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -15,6 +15,7 @@ obj-$(CONFIG_SH_TIMER_TMU)	+= sh_tmu.o
>  obj-$(CONFIG_EM_TIMER_STI)	+= em_sti.o
>  obj-$(CONFIG_CLKBLD_I8253)	+= i8253.o
>  obj-$(CONFIG_CLKSRC_MMIO)	+= mmio.o
> +obj-$(CONFIG_DAVINCI_TIMER)	+= timer-davinci.o
>  obj-$(CONFIG_DIGICOLOR_TIMER)	+= timer-digicolor.o
>  obj-$(CONFIG_OMAP_DM_TIMER)	+= timer-ti-dm.o
>  obj-$(CONFIG_DW_APB_TIMER)	+= dw_apb_timer.o
> diff --git a/drivers/clocksource/timer-davinci.c b/drivers/clocksource/timer-davinci.c
> new file mode 100644
> index 000000000000..d30f81a4088e
> --- /dev/null
> +++ b/drivers/clocksource/timer-davinci.c
> @@ -0,0 +1,272 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +//
> +// TI DaVinci clocksource driver
> +//
> +// Copyright (C) 2019 Texas Instruments
> +// Author: Bartosz Golaszewski <bgolaszewski@...libre.com>
> +// (with tiny parts adopted from code by Kevin Hilman <khilman@...libre.com>)

The header format is wrong, it should be:

// SPDX-License-Identifier: GPL-2.0-only
/*
 * TI DaVinci clocksource driver
 *
 * ...
 * ...
 *
 */

> +#include <linux/clk.h>
> +#include <linux/clockchips.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/sched_clock.h>
> +
> +#include <clocksource/timer-davinci.h>
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) "%s: " fmt "\n", __func__
> +
> +#define DAVINCI_TIMER_REG_TIM12			0x10
> +#define DAVINCI_TIMER_REG_TIM34			0x14
> +#define DAVINCI_TIMER_REG_PRD12			0x18
> +#define DAVINCI_TIMER_REG_PRD34			0x1c
> +#define DAVINCI_TIMER_REG_TCR			0x20
> +#define DAVINCI_TIMER_REG_TGCR			0x24
> +
> +#define DAVINCI_TIMER_TIMMODE_MASK		GENMASK(3, 2)
> +#define DAVINCI_TIMER_RESET_MASK		GENMASK(1, 0)
> +#define DAVINCI_TIMER_TIMMODE_32BIT_UNCHAINED	BIT(2)
> +#define DAVINCI_TIMER_UNRESET			GENMASK(1, 0)
> +
> +#define DAVINCI_TIMER_ENAMODE_MASK		GENMASK(1, 0)
> +#define DAVINCI_TIMER_ENAMODE_DISABLED		0x00
> +#define DAVINCI_TIMER_ENAMODE_ONESHOT		BIT(0)
> +#define DAVINCI_TIMER_ENAMODE_PERIODIC		BIT(1)
> +
> +#define DAVINCI_TIMER_ENAMODE_SHIFT_TIM12	6
> +#define DAVINCI_TIMER_ENAMODE_SHIFT_TIM34	22
> +
> +#define DAVINCI_TIMER_MIN_DELTA			0x01
> +#define DAVINCI_TIMER_MAX_DELTA			0xfffffffe
> +
> +#define DAVINCI_TIMER_TGCR_DEFAULT \
> +		(DAVINCI_TIMER_TIMMODE_32BIT_UNCHAINED | DAVINCI_TIMER_UNRESET)
> +
> +struct davinci_clockevent {
> +	struct clock_event_device dev;
> +	void __iomem *base;
> +
> +	unsigned int tim_off;
> +	unsigned int prd_off;
> +	unsigned int cmp_off;
> +
> +	unsigned int enamode_disabled;
> +	unsigned int enamode_oneshot;
> +	unsigned int enamode_periodic;
> +	unsigned int enamode_mask;
> +};
> +
> +static struct davinci_clockevent *
> +to_davinci_clockevent(struct clock_event_device *clockevent)
> +{
> +	return container_of(clockevent, struct davinci_clockevent, dev);
> +}
> +
> +static unsigned int
> +davinci_clockevent_read(struct davinci_clockevent *clockevent,
> +			unsigned int reg)
> +{
> +	return readl_relaxed(clockevent->base + reg);
> +}
> +
> +static void davinci_clockevent_write(struct davinci_clockevent *clockevent,
> +				     unsigned int reg, unsigned int val)
> +{
> +	writel_relaxed(val, clockevent->base + reg);
> +}
> +
> +static void davinci_reg_update(void __iomem *base, unsigned int reg,
> +			       unsigned int mask, unsigned int val)
> +{
> +	unsigned int new, orig;
> +
> +	orig = readl_relaxed(base + reg);
> +	new = orig & ~mask;
> +	new |= val & mask;
> +
> +	writel_relaxed(new, base + reg);

May be worth to improve this routine?

https://lkml.org/lkml/2019/4/5/837

> +}
> +
> +static void davinci_clockevent_update(struct davinci_clockevent *clockevent,
> +				      unsigned int reg, unsigned int mask,
> +				      unsigned int val)
> +{
> +	davinci_reg_update(clockevent->base, reg, mask, val);
> +}
> +
> +static int
> +davinci_clockevent_set_next_event_std(unsigned long cycles,
> +				      struct clock_event_device *dev)
> +{
> +	struct davinci_clockevent *clockevent;
> +	unsigned int enamode;
> +
> +	clockevent = to_davinci_clockevent(dev);
> +	enamode = clockevent->enamode_disabled;
> +
> +	davinci_clockevent_update(clockevent, DAVINCI_TIMER_REG_TCR,
> +				  clockevent->enamode_mask,
> +				  clockevent->enamode_disabled);

What is for this function with the DAVINCI_TIMER_REG_TCR parameter?

> +	davinci_clockevent_write(clockevent, clockevent->tim_off, 0x0);
> +	davinci_clockevent_write(clockevent, clockevent->prd_off, cycles);
> +
> +	if (clockevent_state_oneshot(&clockevent->dev))
> +		enamode = clockevent->enamode_oneshot;
> +	else if (clockevent_state_periodic(&clockevent->dev))
> +		enamode = clockevent->enamode_periodic;

If none of the conditions above are fulfilled, davinci_clockevent_update
will be called with the default enamode set to enomode_disabled, we
don't want to disable the timer again.

Use the set_state_oneshot / set_state_periodic callbacks to fill the
right value for the 'enamode' and use it unconditionally here.

> +	davinci_clockevent_update(clockevent, DAVINCI_TIMER_REG_TCR,
> +				  clockevent->enamode_mask, enamode);
> +
> +	return 0;
> +}
> +
> +static int
> +davinci_clockevent_set_next_event_cmp(unsigned long cycles,
> +				      struct clock_event_device *dev)
> +{
> +	struct davinci_clockevent *clockevent = to_davinci_clockevent(dev);
> +	unsigned int curr_time;
> +
> +	curr_time = davinci_clockevent_read(clockevent, clockevent->tim_off);
> +	davinci_clockevent_write(clockevent,
> +				 clockevent->cmp_off, curr_time + cycles);
> +
> +	return 0;
> +}
> +
> +static irqreturn_t davinci_timer_irq_timer(int irq, void *data)
> +{
> +	struct davinci_clockevent *clockevent = data;
> +
> +	clockevent->dev.event_handler(&clockevent->dev);


Why isn't disabled here if non-periodic?

And set next event if periodic ?

cf. timer-stm32.c

> +	return IRQ_HANDLED;
> +}
> +
> +static void davinci_timer_init(void __iomem *base)
> +{
> +	/* Set clock to internal mode and disable it. */
> +	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TCR);
> +	/*
> +	 * Reset both 32-bit timers, set no prescaler for timer 34, set the
> +	 * timer to dual 32-bit unchained mode, unreset both 32-bit timers.
> +	 */
> +	writel_relaxed(DAVINCI_TIMER_TGCR_DEFAULT,
> +		       base + DAVINCI_TIMER_REG_TGCR);
> +	/* Init both counters to zero. */
> +	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM12);
> +	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM34);
> +}
> +
> +int __init davinci_timer_register(struct clk *clk,
> +				  const struct davinci_timer_cfg *timer_cfg)
> +{
> +	struct davinci_clockevent *clockevent;
> +	unsigned int tick_rate, shift;
> +	void __iomem *base;
> +	int rv;
> +
> +	rv = clk_prepare_enable(clk);
> +	if (rv) {
> +		pr_err("Unable to prepare and enable the timer clock");
> +		return rv;
> +	}
> +
> +	base = request_mem_region(timer_cfg->reg.start,
> +				  resource_size(&timer_cfg->reg),
> +				  "davinci-timer");
> +	if (!base) {
> +		pr_err("Unable to request memory region");
> +		return -EBUSY;
> +	}
> +
> +	base = ioremap(timer_cfg->reg.start, resource_size(&timer_cfg->reg));
> +	if (!base) {
> +		pr_err("Unable to map the register range");
> +		return -ENOMEM;
> +	}
> +
> +	davinci_timer_init(base);
> +	tick_rate = clk_get_rate(clk);
> +
> +	clockevent = kzalloc(sizeof(*clockevent), GFP_KERNEL);
> +	if (!clockevent) {
> +		pr_err("Error allocating memory for clockevent data");
> +		return -ENOMEM;
> +	}
> +
> +	clockevent->dev.name = "tim12";
> +	clockevent->dev.features = CLOCK_EVT_FEAT_ONESHOT;

If the timer does not have the periodic feature, why all the
enamode_periodic ?

> +	clockevent->dev.cpumask = cpumask_of(0);
> +
> +	clockevent->base = base;
> +	clockevent->tim_off = DAVINCI_TIMER_REG_TIM12;
> +	clockevent->prd_off = DAVINCI_TIMER_REG_PRD12;
> +
> +	shift = DAVINCI_TIMER_ENAMODE_SHIFT_TIM12;
> +	clockevent->enamode_disabled = DAVINCI_TIMER_ENAMODE_DISABLED << shift;
> +	clockevent->enamode_oneshot = DAVINCI_TIMER_ENAMODE_ONESHOT << shift;
> +	clockevent->enamode_periodic = DAVINCI_TIMER_ENAMODE_PERIODIC << shift;
> +	clockevent->enamode_mask = DAVINCI_TIMER_ENAMODE_MASK << shift;

I don't see where 'shift' can be different from TIM12 here neither in
the second patch for those values. Why create these fields instead of
pre-computed macros?


> +	if (timer_cfg->cmp_off) {
> +		clockevent->cmp_off = timer_cfg->cmp_off;
> +		clockevent->dev.set_next_event =
> +				davinci_clockevent_set_next_event_cmp;
> +	} else {
> +		clockevent->dev.set_next_event =
> +				davinci_clockevent_set_next_event_std;
> +	}
> +
> +	rv = request_irq(timer_cfg->irq[DAVINCI_TIMER_CLOCKEVENT_IRQ].start,
> +			 davinci_timer_irq_timer, IRQF_TIMER,
> +			 "clockevent", clockevent);

May be replace "clockevent" by eg. "tim12"?

> +	if (rv) {
> +		pr_err("Unable to request the clockevent interrupt");
> +		return rv;
> +	}
> +
> +	clockevents_config_and_register(&clockevent->dev, tick_rate,
> +					DAVINCI_TIMER_MIN_DELTA,
> +					DAVINCI_TIMER_MAX_DELTA);
> +
> +	return 0;
> +}
> +
> +static int __init of_davinci_timer_register(struct device_node *np)
> +{
> +	struct davinci_timer_cfg timer_cfg = { };
> +	struct clk *clk;
> +	int rv;
> +
> +	rv = of_address_to_resource(np, 0, &timer_cfg.reg);
> +	if (rv) {
> +		pr_err("Unable to get the register range for timer");
> +		return rv;
> +	}
> +
> +	rv = of_irq_to_resource_table(np, timer_cfg.irq,
> +				      DAVINCI_TIMER_NUM_IRQS);
> +	if (rv != DAVINCI_TIMER_NUM_IRQS) {
> +		pr_err("Unable to get the interrupts for timer");
> +		return rv;
> +	}
> +
> +	clk = of_clk_get(np, 0);
> +	if (IS_ERR(clk)) {
> +		pr_err("Unable to get the timer clock");
> +		return PTR_ERR(clk);
> +	}
> +
> +	rv = davinci_timer_register(clk, &timer_cfg);
> +	if (rv)
> +		clk_put(clk);
> +
> +	return rv;
> +}
> +TIMER_OF_DECLARE(davinci_timer, "ti,da830-timer", of_davinci_timer_register);
> diff --git a/include/clocksource/timer-davinci.h b/include/clocksource/timer-davinci.h
> new file mode 100644
> index 000000000000..1dcc1333fbc8
> --- /dev/null
> +++ b/include/clocksource/timer-davinci.h
> @@ -0,0 +1,44 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * TI DaVinci clocksource driver
> + *
> + * Copyright (C) 2019 Texas Instruments
> + * Author: Bartosz Golaszewski <bgolaszewski@...libre.com>
> + */
> +
> +#ifndef __TIMER_DAVINCI_H__
> +#define __TIMER_DAVINCI_H__
> +
> +#include <linux/clk.h>
> +#include <linux/ioport.h>
> +
> +enum {
> +	DAVINCI_TIMER_CLOCKEVENT_IRQ,
> +	DAVINCI_TIMER_CLOCKSOURCE_IRQ,
> +	DAVINCI_TIMER_NUM_IRQS,
> +};
> +
> +/**
> + * struct davinci_timer_cfg - davinci clocksource driver configuration struct
> + * @reg:        register range resource
> + * @irq:        clockevent and clocksource interrupt resources
> + * @cmp_off:    if set - it specifies the compare register used for clockevent
> + *
> + * Note: if the compare register is specified, the driver will use the bottom
> + * clock half for both clocksource and clockevent and the compare register
> + * to generate event irqs. The user must supply the correct compare register
> + * interrupt number.
> + *
> + * This is only used by da830 the DSP of which uses the top half. The timer
> + * driver still configures the top half to run in free-run mode.
> + */
> +struct davinci_timer_cfg {
> +	struct resource reg;
> +	struct resource irq[DAVINCI_TIMER_NUM_IRQS];
> +	unsigned int cmp_off;
> +};
> +
> +int __init davinci_timer_register(struct clk *clk,
> +				  const struct davinci_timer_cfg *data);
> +
> +#endif /* __TIMER_DAVINCI_H__ */
> 


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