Re: [RFC 1/2] clocksource: davinci-timer: add support for clockevents

From: Bartosz Golaszewski
Date: Thu May 23 2019 - 09:01:34 EST

Next message: Miguel Ojeda: "Re: [PATCH 2/2] auxdisplay/ht16k33.c: Convert to use vm_map_pages_zero()"
Previous message: Bartosz Golaszewski: "[RFC v2 1/2] clocksource: davinci-timer: add support for clockevents"
Next in thread: Daniel Lezcano: "Re: [RFC 1/2] clocksource: davinci-timer: add support for clockevents"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

wt., 14 maj 2019 o 21:55 Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> napisaÅ(a):
>
> On 17/04/2019 16:47, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxx>
> > +// (with tiny parts adopted from code by Kevin Hilman <khilman@xxxxxxxxxxxx>)
>
> The header format is wrong, it should be:
>
> // SPDX-License-Identifier: GPL-2.0-only
> /*
> * TI DaVinci clocksource driver
> *
> * ...
> * ...
> *
> */

It's not wrong. It looks like it's at the maintainers discretion and
I've been asked to use both forms by different maintainers. Seems you
just can't get it right. :) I've changed it in v2 though.

>
> > +#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?

I'm not sure I understand the question. :(

>
> > + 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?
>

The variable 'shift' here is only to avoid breaking the lines (just a helper).

The shift itself can be different though in the second patch -
specifically when calling davinci_clocksource_init().

If I were to use predefined values for clockevent, we'd still need
another set of values for clocksource. I think it's clearer the way it
is.

>
> > + 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"?
>

I don't think this is a good idea. Now if you look at /proc/interrupts
you can tell immediately what the interrupt is for ("clockevent").
With "tim12" it's no longer that clear.

> > + 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@xxxxxxxxxxxx>
> > + */
> > +
> > +#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__ */
> >
>
>
> --
> <http://www.linaro.org/> Linaro.org â Open source software for ARM SoCs
>
> Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
> <http://twitter.com/#!/linaroorg> Twitter |
> <http://www.linaro.org/linaro-blog/> Blog
>

For all other comments - they were addressed in v2.

Best regards,
Bartosz Golaszewski

Next message: Miguel Ojeda: "Re: [PATCH 2/2] auxdisplay/ht16k33.c: Convert to use vm_map_pages_zero()"
Previous message: Bartosz Golaszewski: "[RFC v2 1/2] clocksource: davinci-timer: add support for clockevents"
Next in thread: Daniel Lezcano: "Re: [RFC 1/2] clocksource: davinci-timer: add support for clockevents"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]