linux-stable/drivers/clocksource/dw_apb_timer.c
Serge Semin cee43dbf2e clocksource: dw_apb_timer: Make CPU-affiliation being optional
Currently the DW APB Timer driver binds each clockevent timers to a
particular CPU. This isn't good for multiple reasons. First of all seeing
the device is placed on APB bus (which makes it accessible from any CPU
core), accessible over MMIO and having the DYNIRQ flag set we can be sure
that manually binding the timer to any CPU just isn't correct. By doing
so we just set an extra limitation on device usage. This also doesn't
reflect the device actual capability, since by setting the IRQ affinity
we can make it virtually local to any CPU. Secondly imagine if you had a
real CPU-local timer with the same rating and the same CPU-affinity.
In this case if DW APB timer was registered first, then due to the
clockevent framework tick-timer selection procedure we'll end up with the
real CPU-local timer being left unselected for clock-events tracking. But
on most of the platforms (MIPS/ARM/etc) such timers are normally embedded
into the CPU core and are accessible with much better performance then
devices placed on APB. For instance in MIPS architectures there is
r4k-timer, which is CPU-local, assigned with the same rating, and normally
its clockevent device is registered after the platform-specific one.

So in order to fix all of these issues let's make the DW APB Timer CPU
affinity being optional and deactivated by passing a negative CPU id,
which will effectively set the DW APB clockevent timer cpumask to
'cpu_possible_mask'.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-rtc@vger.kernel.org
Cc: devicetree@vger.kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200521204818.25436-5-Sergey.Semin@baikalelectronics.ru
2020-05-23 00:02:41 +02:00

417 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* (C) Copyright 2009 Intel Corporation
* Author: Jacob Pan (jacob.jun.pan@intel.com)
*
* Shared with ARM platforms, Jamie Iles, Picochip 2011
*
* Support for the Synopsys DesignWare APB Timers.
*/
#include <linux/dw_apb_timer.h>
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/slab.h>
#define APBT_MIN_PERIOD 4
#define APBT_MIN_DELTA_USEC 200
#define APBTMR_N_LOAD_COUNT 0x00
#define APBTMR_N_CURRENT_VALUE 0x04
#define APBTMR_N_CONTROL 0x08
#define APBTMR_N_EOI 0x0c
#define APBTMR_N_INT_STATUS 0x10
#define APBTMRS_INT_STATUS 0xa0
#define APBTMRS_EOI 0xa4
#define APBTMRS_RAW_INT_STATUS 0xa8
#define APBTMRS_COMP_VERSION 0xac
#define APBTMR_CONTROL_ENABLE (1 << 0)
/* 1: periodic, 0:free running. */
#define APBTMR_CONTROL_MODE_PERIODIC (1 << 1)
#define APBTMR_CONTROL_INT (1 << 2)
static inline struct dw_apb_clock_event_device *
ced_to_dw_apb_ced(struct clock_event_device *evt)
{
return container_of(evt, struct dw_apb_clock_event_device, ced);
}
static inline struct dw_apb_clocksource *
clocksource_to_dw_apb_clocksource(struct clocksource *cs)
{
return container_of(cs, struct dw_apb_clocksource, cs);
}
static inline u32 apbt_readl(struct dw_apb_timer *timer, unsigned long offs)
{
return readl(timer->base + offs);
}
static inline void apbt_writel(struct dw_apb_timer *timer, u32 val,
unsigned long offs)
{
writel(val, timer->base + offs);
}
static inline u32 apbt_readl_relaxed(struct dw_apb_timer *timer, unsigned long offs)
{
return readl_relaxed(timer->base + offs);
}
static inline void apbt_writel_relaxed(struct dw_apb_timer *timer, u32 val,
unsigned long offs)
{
writel_relaxed(val, timer->base + offs);
}
static void apbt_disable_int(struct dw_apb_timer *timer)
{
u32 ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
ctrl |= APBTMR_CONTROL_INT;
apbt_writel(timer, ctrl, APBTMR_N_CONTROL);
}
/**
* dw_apb_clockevent_pause() - stop the clock_event_device from running
*
* @dw_ced: The APB clock to stop generating events.
*/
void dw_apb_clockevent_pause(struct dw_apb_clock_event_device *dw_ced)
{
disable_irq(dw_ced->timer.irq);
apbt_disable_int(&dw_ced->timer);
}
static void apbt_eoi(struct dw_apb_timer *timer)
{
apbt_readl_relaxed(timer, APBTMR_N_EOI);
}
static irqreturn_t dw_apb_clockevent_irq(int irq, void *data)
{
struct clock_event_device *evt = data;
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
if (!evt->event_handler) {
pr_info("Spurious APBT timer interrupt %d\n", irq);
return IRQ_NONE;
}
if (dw_ced->eoi)
dw_ced->eoi(&dw_ced->timer);
evt->event_handler(evt);
return IRQ_HANDLED;
}
static void apbt_enable_int(struct dw_apb_timer *timer)
{
u32 ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
/* clear pending intr */
apbt_readl(timer, APBTMR_N_EOI);
ctrl &= ~APBTMR_CONTROL_INT;
apbt_writel(timer, ctrl, APBTMR_N_CONTROL);
}
static int apbt_shutdown(struct clock_event_device *evt)
{
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
u32 ctrl;
pr_debug("%s CPU %d state=shutdown\n", __func__,
cpumask_first(evt->cpumask));
ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
ctrl &= ~APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
return 0;
}
static int apbt_set_oneshot(struct clock_event_device *evt)
{
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
u32 ctrl;
pr_debug("%s CPU %d state=oneshot\n", __func__,
cpumask_first(evt->cpumask));
ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
/*
* set free running mode, this mode will let timer reload max
* timeout which will give time (3min on 25MHz clock) to rearm
* the next event, therefore emulate the one-shot mode.
*/
ctrl &= ~APBTMR_CONTROL_ENABLE;
ctrl &= ~APBTMR_CONTROL_MODE_PERIODIC;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
/* write again to set free running mode */
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
/*
* DW APB p. 46, load counter with all 1s before starting free
* running mode.
*/
apbt_writel(&dw_ced->timer, ~0, APBTMR_N_LOAD_COUNT);
ctrl &= ~APBTMR_CONTROL_INT;
ctrl |= APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
return 0;
}
static int apbt_set_periodic(struct clock_event_device *evt)
{
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
unsigned long period = DIV_ROUND_UP(dw_ced->timer.freq, HZ);
u32 ctrl;
pr_debug("%s CPU %d state=periodic\n", __func__,
cpumask_first(evt->cpumask));
ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
ctrl |= APBTMR_CONTROL_MODE_PERIODIC;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
/*
* DW APB p. 46, have to disable timer before load counter,
* may cause sync problem.
*/
ctrl &= ~APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
udelay(1);
pr_debug("Setting clock period %lu for HZ %d\n", period, HZ);
apbt_writel(&dw_ced->timer, period, APBTMR_N_LOAD_COUNT);
ctrl |= APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
return 0;
}
static int apbt_resume(struct clock_event_device *evt)
{
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
pr_debug("%s CPU %d state=resume\n", __func__,
cpumask_first(evt->cpumask));
apbt_enable_int(&dw_ced->timer);
return 0;
}
static int apbt_next_event(unsigned long delta,
struct clock_event_device *evt)
{
u32 ctrl;
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
/* Disable timer */
ctrl = apbt_readl_relaxed(&dw_ced->timer, APBTMR_N_CONTROL);
ctrl &= ~APBTMR_CONTROL_ENABLE;
apbt_writel_relaxed(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
/* write new count */
apbt_writel_relaxed(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT);
ctrl |= APBTMR_CONTROL_ENABLE;
apbt_writel_relaxed(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
return 0;
}
/**
* dw_apb_clockevent_init() - use an APB timer as a clock_event_device
*
* @cpu: The CPU the events will be targeted at or -1 if CPU affiliation
* isn't required.
* @name: The name used for the timer and the IRQ for it.
* @rating: The rating to give the timer.
* @base: I/O base for the timer registers.
* @irq: The interrupt number to use for the timer.
* @freq: The frequency that the timer counts at.
*
* This creates a clock_event_device for using with the generic clock layer
* but does not start and register it. This should be done with
* dw_apb_clockevent_register() as the next step. If this is the first time
* it has been called for a timer then the IRQ will be requested, if not it
* just be enabled to allow CPU hotplug to avoid repeatedly requesting and
* releasing the IRQ.
*/
struct dw_apb_clock_event_device *
dw_apb_clockevent_init(int cpu, const char *name, unsigned rating,
void __iomem *base, int irq, unsigned long freq)
{
struct dw_apb_clock_event_device *dw_ced =
kzalloc(sizeof(*dw_ced), GFP_KERNEL);
int err;
if (!dw_ced)
return NULL;
dw_ced->timer.base = base;
dw_ced->timer.irq = irq;
dw_ced->timer.freq = freq;
clockevents_calc_mult_shift(&dw_ced->ced, freq, APBT_MIN_PERIOD);
dw_ced->ced.max_delta_ns = clockevent_delta2ns(0x7fffffff,
&dw_ced->ced);
dw_ced->ced.max_delta_ticks = 0x7fffffff;
dw_ced->ced.min_delta_ns = clockevent_delta2ns(5000, &dw_ced->ced);
dw_ced->ced.min_delta_ticks = 5000;
dw_ced->ced.cpumask = cpu < 0 ? cpu_possible_mask : cpumask_of(cpu);
dw_ced->ced.features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
dw_ced->ced.set_state_shutdown = apbt_shutdown;
dw_ced->ced.set_state_periodic = apbt_set_periodic;
dw_ced->ced.set_state_oneshot = apbt_set_oneshot;
dw_ced->ced.set_state_oneshot_stopped = apbt_shutdown;
dw_ced->ced.tick_resume = apbt_resume;
dw_ced->ced.set_next_event = apbt_next_event;
dw_ced->ced.irq = dw_ced->timer.irq;
dw_ced->ced.rating = rating;
dw_ced->ced.name = name;
dw_ced->eoi = apbt_eoi;
err = request_irq(irq, dw_apb_clockevent_irq,
IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
dw_ced->ced.name, &dw_ced->ced);
if (err) {
pr_err("failed to request timer irq\n");
kfree(dw_ced);
dw_ced = NULL;
}
return dw_ced;
}
/**
* dw_apb_clockevent_resume() - resume a clock that has been paused.
*
* @dw_ced: The APB clock to resume.
*/
void dw_apb_clockevent_resume(struct dw_apb_clock_event_device *dw_ced)
{
enable_irq(dw_ced->timer.irq);
}
/**
* dw_apb_clockevent_stop() - stop the clock_event_device and release the IRQ.
*
* @dw_ced: The APB clock to stop generating the events.
*/
void dw_apb_clockevent_stop(struct dw_apb_clock_event_device *dw_ced)
{
free_irq(dw_ced->timer.irq, &dw_ced->ced);
}
/**
* dw_apb_clockevent_register() - register the clock with the generic layer
*
* @dw_ced: The APB clock to register as a clock_event_device.
*/
void dw_apb_clockevent_register(struct dw_apb_clock_event_device *dw_ced)
{
apbt_writel(&dw_ced->timer, 0, APBTMR_N_CONTROL);
clockevents_register_device(&dw_ced->ced);
apbt_enable_int(&dw_ced->timer);
}
/**
* dw_apb_clocksource_start() - start the clocksource counting.
*
* @dw_cs: The clocksource to start.
*
* This is used to start the clocksource before registration and can be used
* to enable calibration of timers.
*/
void dw_apb_clocksource_start(struct dw_apb_clocksource *dw_cs)
{
/*
* start count down from 0xffff_ffff. this is done by toggling the
* enable bit then load initial load count to ~0.
*/
u32 ctrl = apbt_readl(&dw_cs->timer, APBTMR_N_CONTROL);
ctrl &= ~APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_cs->timer, ctrl, APBTMR_N_CONTROL);
apbt_writel(&dw_cs->timer, ~0, APBTMR_N_LOAD_COUNT);
/* enable, mask interrupt */
ctrl &= ~APBTMR_CONTROL_MODE_PERIODIC;
ctrl |= (APBTMR_CONTROL_ENABLE | APBTMR_CONTROL_INT);
apbt_writel(&dw_cs->timer, ctrl, APBTMR_N_CONTROL);
/* read it once to get cached counter value initialized */
dw_apb_clocksource_read(dw_cs);
}
static u64 __apbt_read_clocksource(struct clocksource *cs)
{
u32 current_count;
struct dw_apb_clocksource *dw_cs =
clocksource_to_dw_apb_clocksource(cs);
current_count = apbt_readl_relaxed(&dw_cs->timer,
APBTMR_N_CURRENT_VALUE);
return (u64)~current_count;
}
static void apbt_restart_clocksource(struct clocksource *cs)
{
struct dw_apb_clocksource *dw_cs =
clocksource_to_dw_apb_clocksource(cs);
dw_apb_clocksource_start(dw_cs);
}
/**
* dw_apb_clocksource_init() - use an APB timer as a clocksource.
*
* @rating: The rating to give the clocksource.
* @name: The name for the clocksource.
* @base: The I/O base for the timer registers.
* @freq: The frequency that the timer counts at.
*
* This creates a clocksource using an APB timer but does not yet register it
* with the clocksource system. This should be done with
* dw_apb_clocksource_register() as the next step.
*/
struct dw_apb_clocksource *
dw_apb_clocksource_init(unsigned rating, const char *name, void __iomem *base,
unsigned long freq)
{
struct dw_apb_clocksource *dw_cs = kzalloc(sizeof(*dw_cs), GFP_KERNEL);
if (!dw_cs)
return NULL;
dw_cs->timer.base = base;
dw_cs->timer.freq = freq;
dw_cs->cs.name = name;
dw_cs->cs.rating = rating;
dw_cs->cs.read = __apbt_read_clocksource;
dw_cs->cs.mask = CLOCKSOURCE_MASK(32);
dw_cs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;
dw_cs->cs.resume = apbt_restart_clocksource;
return dw_cs;
}
/**
* dw_apb_clocksource_register() - register the APB clocksource.
*
* @dw_cs: The clocksource to register.
*/
void dw_apb_clocksource_register(struct dw_apb_clocksource *dw_cs)
{
clocksource_register_hz(&dw_cs->cs, dw_cs->timer.freq);
}
/**
* dw_apb_clocksource_read() - read the current value of a clocksource.
*
* @dw_cs: The clocksource to read.
*/
u64 dw_apb_clocksource_read(struct dw_apb_clocksource *dw_cs)
{
return (u64)~apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE);
}