[PATCH] riscv: Access time mmio instead of rdtime.

[Djordje Todorovic]

HTEC Public

Thanks a lot for your feedback. We will address those comments in
the v2 for the change.

Best,
Djordje

________________________________________
From: Palmer Dabbelt <palmer at dabbelt.com>
Sent: Wednesday, February 5, 2025 4:31 PM
To: Conor Dooley <conor at kernel.org>
Cc: arikalo at gmail.com <arikalo at gmail.com>; linux-riscv at lists.infradead.org <linux-riscv at lists.infradead.org>; Paul Walmsley <paul.walmsley at sifive.com>; aou at eecs.berkeley.edu <aou at eecs.berkeley.edu>; daniel.lezcano at linaro.org <daniel.lezcano at linaro.org>; tglx at linutronix.de <tglx at linutronix.de>; Djordje Todorovic <djordje.todorovic at htecgroup.com>; Dragan.Mladjenovic at syrmia.com <Dragan.Mladjenovic at syrmia.com>; linux-kernel at vger.kernel.org <linux-kernel at vger.kernel.org>
Subject: Re: [PATCH] riscv: Access time mmio instead of rdtime.

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On Sun, 29 Dec 2024 07:09:13 PST (-0800), Conor Dooley wrote:
> On Fri, Dec 27, 2024 at 04:00:56PM +0100, Aleksandar Rikalo wrote:
>> +#if defined(CONFIG_RISCV_TIME_MMIO)
>> +    if (!of_property_read_u64(n, "clock-reg", &mmio_addr)) {
>
> This is a non-standard, undocumented property. reg & reg-names are what
> you should be using here.

We were talking some in the patchwork meeting.  If this system has a
CLINT then it's probably best to refactor the timers such that MMIO
CLINT access is independent from M-mode (as there's some patches
floating around to make M-mode use rdtime on systems that implement
rdtime).

>> +            riscv_time_val = ioremap((long)mmio_addr, 8);
>> +            if (riscv_time_val) {
>> +                    pr_info("Using mmio time register at 0x%llx\n", mmio_addr);
>> +                    static_branch_enable(&riscv_time_mmio_available);
>> +            } else {
>> +                    pr_warn("Unable to use mmio time at 0x%llx\n", mmio_addr);
>> +            }
>> +    }
>> +#endif