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Message-ID: <5a8e8af8a81fac84e13f9ece46a73028243ff276.camel@gmail.com>
Date: Sun, 04 Jun 2023 17:49:31 +0200
From: Alexander Sverdlin <alexander.sverdlin@...il.com>
To: Nikita Shubin <nikita.shubin@...uefel.me>,
Arnd Bergmann <arnd@...db.de>,
Linus Walleij <linus.walleij@...aro.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>
Cc: Michael Peters <mpeters@...eddedTS.com>,
Kris Bahnsen <kris@...eddedTS.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 09/43] clocksource: ep93xx: Add driver for Cirrus
Logic EP93xx
On Thu, 2023-06-01 at 08:34 +0300, Nikita Shubin wrote:
> This us a rewrite of EP93xx timer driver in
> arch/arm/mach-ep93xx/timer-ep93xx.c trying to do everything
> the device tree way:
>
> - Make every IO-access relative to a base address and dynamic
> so we can do a dynamic ioremap and get going.
> - Find register range and interrupt from the device tree.
>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Nikita Shubin <nikita.shubin@...uefel.me>
Tested-by: Alexander Sverdlin <alexander.sverdlin@...il.com>
> ---
>
> Notes:
> v0 -> v1:
>
> - fixed headers
>
> drivers/clocksource/Kconfig | 11 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-ep93xx.c | 189 +++++++++++++++++++++++++++++
> 3 files changed, 201 insertions(+)
> create mode 100644 drivers/clocksource/timer-ep93xx.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 5fc8f0e7fb38..40bfc7c86756 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -721,4 +721,15 @@ config GOLDFISH_TIMER
> help
> Support for the timer/counter of goldfish-rtc
>
> +config EP93XX_TIMER
> + bool "Cirrus Logic ep93xx timer driver" if COMPILE_TEST
> + depends on ARCH_EP93XX
> + depends on GENERIC_CLOCKEVENTS
> + depends on HAS_IOMEM
> + select CLKSRC_MMIO
> + select TIMER_OF
> + help
> + Enables support for the Cirrus Logic timer block
> + EP93XX.
> +
> endmenu
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 64ab547de97b..09c2d4e5d809 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -88,3 +88,4 @@ obj-$(CONFIG_MICROCHIP_PIT64B) += timer-microchip-pit64b.o
> obj-$(CONFIG_MSC313E_TIMER) += timer-msc313e.o
> obj-$(CONFIG_GOLDFISH_TIMER) += timer-goldfish.o
> obj-$(CONFIG_GXP_TIMER) += timer-gxp.o
> +obj-$(CONFIG_EP93XX_TIMER) += timer-ep93xx.o
> diff --git a/drivers/clocksource/timer-ep93xx.c b/drivers/clocksource/timer-ep93xx.c
> new file mode 100644
> index 000000000000..966502169aa0
> --- /dev/null
> +++ b/drivers/clocksource/timer-ep93xx.c
> @@ -0,0 +1,189 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Cirrus Logic EP93xx timer driver.
> + * Copyright (C) 2021 Nikita Shubin <nikita.shubin@...uefel.me>
> + *
> + * Based on a rewrite of arch/arm/mach-ep93xx/timer.c:
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/sched_clock.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_address.h>
> +#include <linux/io.h>
> +#include <asm/mach/time.h>
> +
> +/*************************************************************************
> + * Timer handling for EP93xx
> + *************************************************************************
> + * The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and
> + * 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
> + * an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz,
> + * is free-running, and can't generate interrupts.
> + *
> + * The 508 kHz timers are ideal for use for the timer interrupt, as the
> + * most common values of HZ divide 508 kHz nicely. We pick the 32 bit
> + * timer (timer 3) to get as long sleep intervals as possible when using
> + * CONFIG_NO_HZ.
> + *
> + * The higher clock rate of timer 4 makes it a better choice than the
> + * other timers for use as clock source and for sched_clock(), providing
> + * a stable 40 bit time base.
> + *************************************************************************
> + */
> +
> +#define EP93XX_TIMER1_LOAD 0x00
> +#define EP93XX_TIMER1_VALUE 0x04
> +#define EP93XX_TIMER1_CONTROL 0x08
> +#define EP93XX_TIMER123_CONTROL_ENABLE BIT(7)
> +#define EP93XX_TIMER123_CONTROL_MODE BIT(6)
> +#define EP93XX_TIMER123_CONTROL_CLKSEL BIT(3)
> +#define EP93XX_TIMER1_CLEAR 0x0c
> +#define EP93XX_TIMER2_LOAD 0x20
> +#define EP93XX_TIMER2_VALUE 0x24
> +#define EP93XX_TIMER2_CONTROL 0x28
> +#define EP93XX_TIMER2_CLEAR 0x2c
> +/* This read-only register contains the low word of the time stamp debug timer
> + * ( Timer4). When this register is read, the high byte of the Timer4 counter is
> + * saved in the Timer4ValueHigh register.
> + */
> +#define EP93XX_TIMER4_VALUE_LOW 0x60
> +#define EP93XX_TIMER4_VALUE_HIGH 0x64
> +#define EP93XX_TIMER4_VALUE_HIGH_ENABLE BIT(8)
> +#define EP93XX_TIMER3_LOAD 0x80
> +#define EP93XX_TIMER3_VALUE 0x84
> +#define EP93XX_TIMER3_CONTROL 0x88
> +#define EP93XX_TIMER3_CLEAR 0x8c
> +
> +#define EP93XX_TIMER123_RATE 508469
> +#define EP93XX_TIMER4_RATE 983040
> +
> +struct ep93xx_tcu {
> + void __iomem *base;
> +};
> +
> +static struct ep93xx_tcu *ep93xx_tcu;
> +
> +static u64 ep93xx_clocksource_read(struct clocksource *c)
> +{
> + struct ep93xx_tcu *tcu = ep93xx_tcu;
> + u64 ret;
> +
> + ret = readl(tcu->base + EP93XX_TIMER4_VALUE_LOW);
> + ret |= ((u64) (readl(tcu->base + EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32);
> + return (u64) ret;
> +}
> +
> +static u64 notrace ep93xx_read_sched_clock(void)
> +{
> + return ep93xx_clocksource_read(NULL);
> +}
> +
> +static int ep93xx_clkevt_set_next_event(unsigned long next,
> + struct clock_event_device *evt)
> +{
> + struct ep93xx_tcu *tcu = ep93xx_tcu;
> + /* Default mode: periodic, off, 508 kHz */
> + u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
> + EP93XX_TIMER123_CONTROL_CLKSEL;
> +
> + /* Clear timer */
> + writel(tmode, tcu->base + EP93XX_TIMER3_CONTROL);
> +
> + /* Set next event */
> + writel(next, tcu->base + EP93XX_TIMER3_LOAD);
> + writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
> + tcu->base + EP93XX_TIMER3_CONTROL);
> + return 0;
> +}
> +
> +static int ep93xx_clkevt_shutdown(struct clock_event_device *evt)
> +{
> + struct ep93xx_tcu *tcu = ep93xx_tcu;
> + /* Disable timer */
> + writel(0, tcu->base + EP93XX_TIMER3_CONTROL);
> +
> + return 0;
> +}
> +
> +static struct clock_event_device ep93xx_clockevent = {
> + .name = "timer1",
> + .features = CLOCK_EVT_FEAT_ONESHOT,
> + .set_state_shutdown = ep93xx_clkevt_shutdown,
> + .set_state_oneshot = ep93xx_clkevt_shutdown,
> + .tick_resume = ep93xx_clkevt_shutdown,
> + .set_next_event = ep93xx_clkevt_set_next_event,
> + .rating = 300,
> +};
> +
> +static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
> +{
> + struct ep93xx_tcu *tcu = ep93xx_tcu;
> + struct clock_event_device *evt = dev_id;
> +
> + /* Writing any value clears the timer interrupt */
> + writel(1, tcu->base + EP93XX_TIMER3_CLEAR);
> +
> + evt->event_handler(evt);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int __init ep93xx_timer_of_init(struct device_node *np)
> +{
> + int irq;
> + unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL;
> + struct ep93xx_tcu *tcu;
> + int ret;
> +
> + tcu = kzalloc(sizeof(*tcu), GFP_KERNEL);
> + if (!tcu)
> + return -ENOMEM;
> +
> + tcu->base = of_iomap(np, 0);
> + if (!tcu->base) {
> + pr_err("Can't remap registers\n");
> + ret = -ENXIO;
> + goto out_free;
> + }
> +
> + ep93xx_tcu = tcu;
> +
> + irq = irq_of_parse_and_map(np, 0);
> + if (irq <= 0) {
> + pr_err("ERROR: invalid interrupt number\n");
> + ret = -EINVAL;
> + goto out_free;
> + }
> +
> + /* Enable and register clocksource and sched_clock on timer 4 */
> + writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
> + tcu->base + EP93XX_TIMER4_VALUE_HIGH);
> + clocksource_mmio_init(NULL, "timer4",
> + EP93XX_TIMER4_RATE, 200, 40,
> + ep93xx_clocksource_read);
> + sched_clock_register(ep93xx_read_sched_clock, 40,
> + EP93XX_TIMER4_RATE);
> +
> + /* Set up clockevent on timer 3 */
> + if (request_irq(irq, ep93xx_timer_interrupt, flags, "ep93xx timer",
> + &ep93xx_clockevent))
> + pr_err("Failed to request irq %d (ep93xx timer)\n", irq);
> + clockevents_config_and_register(&ep93xx_clockevent,
> + EP93XX_TIMER123_RATE,
> + 1,
> + 0xffffffffU);
> +
> + return 0;
> +
> +out_free:
> + kfree(tcu);
> + return ret;
> +}
> +
> +TIMER_OF_DECLARE(ep93xx_timer, "cirrus,ep9301-timer", ep93xx_timer_of_init);
--
Alexander Sverdlin.
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