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Message-ID: <54C60C4F.50507@linaro.org>
Date: Mon, 26 Jan 2015 10:43:43 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Baruch Siach <baruch@...s.co.il>,
Thomas Gleixner <tglx@...utronix.de>
CC: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 2/2] clocksource: driver for Conexant Digicolor SoC
timer
On 01/26/2015 08:56 AM, Baruch Siach wrote:
> Add clocksource driver to the Conexant CX92755 SoC, part of the Digicolor SoCs
> series. Hardware provides 8 timers, A to H. Timer A is dedicated to a future
> watchdog driver so we don't use it here. Use timer B for sched_clock, and timer
> C for clock_event.
>
> Signed-off-by: Baruch Siach <baruch@...s.co.il>
> ---
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-digicolor.c | 170 ++++++++++++++++++++++++++++++++++
> 2 files changed, 171 insertions(+)
> create mode 100644 drivers/clocksource/timer-digicolor.c
>
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 94d90b24b56b..a993c108be67 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -10,6 +10,7 @@ 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-$(CONFIG_ARCH_DIGICOLOR) += timer-digicolor.o
> obj-$(CONFIG_DW_APB_TIMER) += dw_apb_timer.o
> obj-$(CONFIG_DW_APB_TIMER_OF) += dw_apb_timer_of.o
> obj-$(CONFIG_CLKSRC_NOMADIK_MTU) += nomadik-mtu.o
> diff --git a/drivers/clocksource/timer-digicolor.c b/drivers/clocksource/timer-digicolor.c
> new file mode 100644
> index 000000000000..c97ea7eac4a5
> --- /dev/null
> +++ b/drivers/clocksource/timer-digicolor.c
> @@ -0,0 +1,170 @@
> +/*
> + * Conexant Digicolor timer driver
> + *
> + * Author: Baruch Siach <baruch@...s.co.il>
> + *
> + * Copyright (C) 2014 Paradox Innovation Ltd.
> + *
> + * Based on:
> + * Allwinner SoCs hstimer driver
> + *
> + * Copyright (C) 2013 Maxime Ripard
> + *
> + * Maxime Ripard <maxime.ripard@...e-electrons.com>
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +/*
> + * Conexant Digicolor SoCs have 8 configurable timers, named from "Timer A" to
> + * "Timer H". Timer A is the only one with watchdog support, so it is dedicated
> + * to the watchdog driver. This driver uses Timer B for sched_clock(), and
> + * Timer C for clockevents.
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/clk.h>
> +#include <linux/clockchips.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/irqreturn.h>
> +#include <linux/sched_clock.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +
> +enum {
> + TIMER_A,
> + TIMER_B,
> + TIMER_C,
> + TIMER_D,
> + TIMER_E,
> + TIMER_F,
> + TIMER_G,
> + TIMER_H,
> +};
> +
> +#define CONTROL(t) ((t)*8)
> +#define COUNT(t) ((t)*8 + 4)
> +
> +#define CONTROL_DISABLE 0
> +#define CONTROL_ENABLE BIT(0)
> +#define CONTROL_MODE(m) ((m) << 4)
> +#define CONTROL_MODE_ONESHOT CONTROL_MODE(1)
> +#define CONTROL_MODE_PERIODIC CONTROL_MODE(2)
> +
> +static struct dc_dev_t {
> + void __iomem *timer_base;
> + u32 ticks_per_jiffy;
> +} dc_dev;
Hi Baruch,
your code is valid but I think there is a misunderstanding when we
talked about the encapsulation.
I was expecting something like:
static struct digicolor_timer {
void __iomem *base;
u32 ticks_per_jiffy;
int channel;
struct clock_event_device ce;
};
struct digicolor_timer *dg_timer(struct clock_event_device *ce)
{
return container_of(ce, struct digicolor_timer, ce);
}
So the timer could be accessed directly from the clock_event_device
structure. The exception is the 'sched_read' and the init function where
you will have to address directly the global variable.
Perhaps, that would be nice if you take the opportunity to encapsulate
the enable/disable functions.
static inline void dg_timer_disable(struct clock_event_device *ce)
{
struct digital_timer *dt = dg_timer(ce);
writeb(CONTROL_DISABLE, dt->base + CONTROL(dt->channel));
}
static inline void dg_timer_enable(struct clock_event_device *ce, int mode)
{
struct digital_timer *dt = dg_timer(ce);
writeb(CONTROL_ENABLE | mode, dt->base, CONTROL(dt->channel));
}
> +
> +static void digicolor_clkevt_mode(enum clock_event_mode mode,
> + struct clock_event_device *clk)
IMO, 'clk' argument name is confusing. I would suggest to use 'ce' or
whatever.
> +{
> + switch (mode) {
> + case CLOCK_EVT_MODE_PERIODIC:
> + writeb(CONTROL_DISABLE, dc_dev.timer_base + CONTROL(TIMER_C));
> + writel(dc_dev.ticks_per_jiffy,
> + dc_dev.timer_base + COUNT(TIMER_C));
> + writeb(CONTROL_ENABLE | CONTROL_MODE_PERIODIC,
> + dc_dev.timer_base + CONTROL(TIMER_C));
Becomes:
dg_timer_disable(ce);
dg_timer_enable(ce, CONTROL_MODE_PERIODIC);
...
> + break;
> + case CLOCK_EVT_MODE_ONESHOT:
> + writeb(CONTROL_DISABLE, dc_dev.timer_base + CONTROL(TIMER_C));
> + writeb(CONTROL_ENABLE | CONTROL_MODE_ONESHOT,
> + dc_dev.timer_base + CONTROL(TIMER_C));
Becomes:
dg_timer_disable(ce);
dg_timer_enable(ce, CONTROL_MODE_ONESHOT);
> + break;
> + case CLOCK_EVT_MODE_UNUSED:
> + case CLOCK_EVT_MODE_SHUTDOWN:
> + default:
> + writeb(CONTROL_DISABLE, dc_dev.timer_base + CONTROL(TIMER_C));
Becomes:
dg_timer_disable(ce);
> + break;
> + }
> +}
> +
> +static int digicolor_clkevt_next_event(unsigned long evt,
> + struct clock_event_device *unused)
> +{
> + writeb(CONTROL_DISABLE, dc_dev.timer_base + CONTROL(TIMER_C));
> + writel(evt, dc_dev.timer_base + COUNT(TIMER_C));
> + writeb(CONTROL_ENABLE | CONTROL_MODE_ONESHOT,
> + dc_dev.timer_base + CONTROL(TIMER_C));
Becomes:
dg_timer_disable(ce);
writel(evt, dg_timer(ce)->base + COUNT(dg_timer(ce)->base));
dg_timer_enable(ce, CONTROL_MODE_ONESHOT);
> + return 0;
> +}
> +
> +static struct clock_event_device digicolor_clockevent = {
> + .name = "digicolor_tick",
> + .rating = 340,
> + .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
> + .set_mode = digicolor_clkevt_mode,
> + .set_next_event = digicolor_clkevt_next_event,
> +};
struct digicolor_timer dg_timer = {
.ce = {
.name = "digicolor_tick",
.rating = 340,
.features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT,
.set_mode = digicolor_clkevt_mode,
.set_next_event = digicolor_clkevt_next_event,
},
.channel = TIMER_C,
};
What do you think ?
> +static irqreturn_t digicolor_timer_interrupt(int irq, void *dev_id)
> +{
> + struct clock_event_device *evt = dev_id;
> +
> + evt->event_handler(evt);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static u64 digicolor_timer_sched_read(void)
> +{
> + return ~readl(dc_dev.timer_base + COUNT(TIMER_B));
> +}
> +
> +static void __init digicolor_timer_init(struct device_node *node)
> +{
> + unsigned long rate;
> + struct clk *clk;
> + int ret, irq;
> +
> + dc_dev.timer_base =
> + of_io_request_and_map(node, 0, of_node_full_name(node));
> + if (!dc_dev.timer_base) {
> + pr_err("Can't map registers");
> + return;
> + }
> +
> + irq = irq_of_parse_and_map(node, TIMER_C);
> + if (irq <= 0) {
> + pr_err("Can't parse IRQ");
> + return;
> + }
> +
> + clk = of_clk_get(node, 0);
> + if (IS_ERR(clk)) {
> + pr_err("Can't get timer clock");
> + return;
> + }
> + clk_prepare_enable(clk);
> + rate = clk_get_rate(clk);
> + dc_dev.ticks_per_jiffy = DIV_ROUND_UP(rate, HZ);
> +
> + writeb(CONTROL_DISABLE, dc_dev.timer_base + CONTROL(TIMER_B));
> + writel(UINT_MAX, dc_dev.timer_base + COUNT(TIMER_B));
> + writeb(CONTROL_ENABLE, dc_dev.timer_base + CONTROL(TIMER_B));
> +
> + sched_clock_register(digicolor_timer_sched_read, 32, rate);
> + clocksource_mmio_init(dc_dev.timer_base + COUNT(TIMER_B), node->name,
> + rate, 340, 32, clocksource_mmio_readl_down);
> +
> + ret = request_irq(irq, digicolor_timer_interrupt,
> + IRQF_TIMER | IRQF_IRQPOLL, "digicolor_timerC",
> + &digicolor_clockevent);
> + if (ret)
> + pr_warn("request of timer irq %d failed (%d)\n", irq, ret);
> +
> + digicolor_clockevent.cpumask = cpu_possible_mask;
> + digicolor_clockevent.irq = irq;
> +
> + clockevents_config_and_register(&digicolor_clockevent, rate, 0,
> + 0xffffffff);
> +}
> +CLOCKSOURCE_OF_DECLARE(conexant_digicolor, "cnxt,cx92755-timer",
> + digicolor_timer_init);
>
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