From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Anup Patel <anup.patel@wdc.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Rob Herring <robh+dt@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>
Cc: devicetree@vger.kernel.org,
Damien Le Moal <damien.lemoal@wdc.com>,
Emil Renner Berhing <kernel@esmil.dk>,
Anup Patel <anup@brainfault.org>,
linux-kernel@vger.kernel.org, Atish Patra <atish.patra@wdc.com>,
Alistair Francis <Alistair.Francis@wdc.com>,
linux-riscv@lists.infradead.org
Subject: Re: [PATCH v4 2/4] clocksource/drivers: Add CLINT timer driver
Date: Tue, 21 Jul 2020 13:02:45 +0200 [thread overview]
Message-ID: <63f65ddd-b7c4-b8fd-151c-a77e8c87efed@linaro.org> (raw)
In-Reply-To: <20200717075101.263332-3-anup.patel@wdc.com>
On 17/07/2020 09:50, Anup Patel wrote:
> We add a separate CLINT timer driver for Linux RISC-V M-mode (i.e.
> RISC-V NoMMU kernel).
>
> The CLINT MMIO device provides three things:
> 1. 64bit free running counter register
> 2. 64bit per-CPU time compare registers
> 3. 32bit per-CPU inter-processor interrupt registers
>
> Unlike other timer devices, CLINT provides IPI registers along with
> timer registers. To use CLINT IPI registers, the CLINT timer driver
> provides IPI related callbacks to arch/riscv.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Tested-by: Emil Renner Berhing <kernel@esmil.dk>
> ---
> drivers/clocksource/Kconfig | 9 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-clint.c | 231 ++++++++++++++++++++++++++++++
> include/linux/cpuhotplug.h | 1 +
> 4 files changed, 242 insertions(+)
> create mode 100644 drivers/clocksource/timer-clint.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 91418381fcd4..e1ce0d510a03 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -658,6 +658,15 @@ config RISCV_TIMER
> is accessed via both the SBI and the rdcycle instruction. This is
> required for all RISC-V systems.
>
> +config CLINT_TIMER
> + bool "Timer for the RISC-V platform"
> + depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
> + select TIMER_PROBE
> + select TIMER_OF
> + help
> + This option enables the CLINT timer for RISC-V systems. The CLINT
> + driver is usually used for NoMMU RISC-V systems.
V3 has a comment about fixing the Kconfig option.
[ ... ]
> +{
> + bool *registered = per_cpu_ptr(&clint_clock_event_registered, cpu);
> + struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
> +
> + if (!(*registered)) {
> + ce->cpumask = cpumask_of(cpu);
> + clockevents_config_and_register(ce, clint_timer_freq, 200,
> + ULONG_MAX);
> + *registered = true;
> + }
I was unsure about the clockevents_config_and_register() multiple calls
when doing the comment. It seems like it is fine to call it several
times and that is done in several places like riscv or arch_arm_timer.
It is probably safe to drop the 'registered' code here, sorry for the
confusion.
> + enable_percpu_irq(clint_timer_irq,
> + irq_get_trigger_type(clint_timer_irq));
> + return 0;
> +}
> +
[ ... ]
--
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next prev parent reply other threads:[~2020-07-21 11:03 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 7:50 [PATCH v4 0/4] Dedicated CLINT timer driver Anup Patel
2020-07-17 7:50 ` [PATCH v4 1/4] RISC-V: Add mechanism to provide custom IPI operations Anup Patel
2020-07-21 0:46 ` Atish Patra
2020-07-17 7:50 ` [PATCH v4 2/4] clocksource/drivers: Add CLINT timer driver Anup Patel
2020-07-21 1:11 ` Atish Patra
2020-07-21 11:43 ` Anup Patel
2020-07-21 19:39 ` Atish Patra
2020-07-21 11:02 ` Daniel Lezcano [this message]
2020-07-21 11:49 ` Anup Patel
2020-07-21 12:15 ` Daniel Lezcano
2020-07-22 3:36 ` Anup Patel
2020-07-17 7:51 ` [PATCH v4 3/4] RISC-V: Remove CLINT related code from timer and arch Anup Patel
2020-07-17 7:51 ` [PATCH v4 4/4] dt-bindings: timer: Add CLINT bindings Anup Patel
2020-07-21 1:15 ` Atish Patra
2020-07-21 11:39 ` Anup Patel
2020-07-21 12:17 ` Sean Anderson
2020-07-22 3:55 ` Anup Patel
2020-07-26 18:37 ` Palmer Dabbelt
2020-07-27 11:47 ` Sean Anderson
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