Date:   Wed, 7 Jun 2017 22:16:59 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
        albert@...ive.com, patches@...ups.riscv.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 09/17] clocksource/timer-riscv: New RISC-V Clocksource

Hi,

I prefer the term 'timer' when we have a clocksource + clockevent.

Reply-To: 
In-Reply-To: <CAMuHMdXkO-r1kVow-PqyRNYy32Eq5jr9fn75neFcMWhDUvGCPA@...l.gmail.com>

On Wed, Jun 07, 2017 at 09:12:28AM +0200, Geert Uytterhoeven wrote:
> CC clocksource folks

Thanks Geert.
 
> On Wed, Jun 7, 2017 at 12:59 AM, Palmer Dabbelt <palmer@...belt.com> wrote:
> > The RISC-V ISA defines a single RTC as well as an SBI oneshot timer.
> > This timer is present on all RISC-V systems.

As it is a new driver, please give a detailed description of the timer for the
record.

> > Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
> > ---
> >  drivers/clocksource/Kconfig       |   8 +++
> >  drivers/clocksource/Makefile      |   1 +
> >  drivers/clocksource/timer-riscv.c | 118 ++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 127 insertions(+)
> >  create mode 100644 drivers/clocksource/timer-riscv.c
> >
> > diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> > index 545d541ae20e..1c2c6e7c7fab 100644
> > --- a/drivers/clocksource/Kconfig
> > +++ b/drivers/clocksource/Kconfig
> > @@ -612,4 +612,12 @@ config CLKSRC_ST_LPC
> >           Enable this option to use the Low Power controller timer
> >           as clocksource.
> >
> > +config CLKSRC_RISCV

config TIMER_RISCV

> > +       #bool "Clocksource for the RISC-V platform"
> > +       def_bool y if RISCV
> > +       depends on RISCV
> > +       help
> > +         This enables a clocksource based on the RISC-V SBI timer, which is
> > +         built in to all RISC-V systems.

Please stick to the other drivers options format.

 ... if COMPILE_TEST ...

And set the timer from the platform's Kconfig.

> >  endmenu
> > diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> > index 2b5b56a6f00f..408ed9d314dc 100644
> > --- a/drivers/clocksource/Makefile
> > +++ b/drivers/clocksource/Makefile
> > @@ -73,3 +73,4 @@ obj-$(CONFIG_H8300_TMR16)             += h8300_timer16.o
> >  obj-$(CONFIG_H8300_TPU)                        += h8300_tpu.o
> >  obj-$(CONFIG_CLKSRC_ST_LPC)            += clksrc_st_lpc.o
> >  obj-$(CONFIG_X86_NUMACHIP)             += numachip.o
> > +obj-$(CONFIG_CLKSRC_RISCV)             += timer-riscv.o
> > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > new file mode 100644
> > index 000000000000..04ef7b9130b3
> > --- /dev/null
> > +++ b/drivers/clocksource/timer-riscv.c
> > @@ -0,0 +1,118 @@
> > +/*
> > + * Copyright (C) 2012 Regents of the University of California
> > + * Copyright (C) 2017 SiFive
> > + *
> > + *   This program is free software; you can redistribute it and/or
> > + *   modify it under the terms of the GNU General Public License
> > + *   as published by the Free Software Foundation, version 2.
> > + *
> > + *   This program is distributed in the hope that it will be useful,
> > + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + *   GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/clocksource.h>
> > +#include <linux/clockchips.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/irq.h>
> > +#include <linux/delay.h>
> > +#include <linux/of.h>
> > +
> > +#include <asm/irq.h>
> > +#include <asm/csr.h>
> > +#include <asm/sbi.h>
> > +#include <asm/delay.h>

Are all these headers needed?

I don't see in the code a delay.

Please remove these asm headers and add the missing macros in this file.

> > +unsigned long riscv_timebase;

It is pointless to have this global variable.

> > +static DEFINE_PER_CPU(struct clock_event_device, clock_event);

The description tells there is one clockevent but here we have percpu
clockevents. Either the description is inaccurate or the percpu code is wrong.

> > +static int riscv_timer_set_next_event(unsigned long delta,
> > +       struct clock_event_device *evdev)

indent.

> > +{
> > +       sbi_set_timer(get_cycles() + delta);
> > +       return 0;
> > +}
> > +
> > +static int riscv_timer_set_oneshot(struct clock_event_device *evt)
> > +{
> > +       /* no-op; only one mode */
> > +       return 0;
> > +}
> > +
> > +static int riscv_timer_set_shutdown(struct clock_event_device *evt)
> > +{
> > +       /* can't stop the clock! */
> > +       return 0;
> > +}
> > +
> > +static u64 riscv_rdtime(struct clocksource *cs)
> > +{
> > +       return get_cycles();
> > +}
> > +
> > +static struct clocksource riscv_clocksource = {
> > +       .name = "riscv_clocksource",
> > +       .rating = 300,
> > +       .read = riscv_rdtime,
> > +#ifdef CONFIG_64BITS
> > +       .mask = CLOCKSOURCE_MASK(64),
> > +#else
> > +       .mask = CLOCKSOURCE_MASK(32),
> > +#endif /* CONFIG_64BITS */
> > +       .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> > +};

Consider using clocksource_mmio_init().

> > +void riscv_timer_interrupt(void)

static.

> > +{
> > +       int cpu = smp_processor_id();
> > +       struct clock_event_device *evdev = &per_cpu(clock_event, cpu);
> > +
> > +       evdev->event_handler(evdev);
> > +}

riscv_timer_interrupt() not used.

Wrong function signature for an interrupt handler.

Missing IRQ_HANDLED returned value.

> > +void __init init_clockevent(void)

static.

> > +{
> > +       int cpu = smp_processor_id();
> > +       struct clock_event_device *ce = &per_cpu(clock_event, cpu);
> > +
> > +       *ce = (struct clock_event_device){
> > +               .name = "riscv_timer_clockevent",
> > +               .features = CLOCK_EVT_FEAT_ONESHOT,
> > +               .rating = 300,
> > +               .cpumask = cpumask_of(cpu),
> > +               .set_next_event = riscv_timer_set_next_event,
> > +               .set_state_oneshot  = riscv_timer_set_oneshot,
> > +               .set_state_shutdown = riscv_timer_set_shutdown,
> > +       };
> > +
> > +       /* Enable timer interrupts */
> > +       csr_set(sie, SIE_STIE);

Where is the request_irq call?

> > +       clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
> > +}
> > +
> > +static unsigned long __init of_timebase(void)
> > +{
> > +       struct device_node *cpu;
> > +       const __be32 *prop;
> > +
> > +       cpu = of_find_node_by_path("/cpus");
> > +       if (cpu) {
> > +               prop = of_get_property(cpu, "timebase-frequency", NULL);
> > +               if (prop)
> > +                       return be32_to_cpu(*prop);
> > +       }

Couldn't this be replaced by a clock?

> > +
> > +       return 10000000;

Macro please.

> > +}
> > +
> > +void __init time_init(void)
> > +{
> > +       riscv_timebase = of_timebase();
> > +       lpj_fine = riscv_timebase / HZ;

Where is used lpj_fine ?

> > +       clocksource_register_hz(&riscv_clocksource, riscv_timebase);
> > +       init_clockevent();
> > +}

I don't have the context, from where is called this function (time_init())?

-- 

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