linux-kernel - Re: [PATCH v19 10/15] clocksource/drivers/arm_arch_timer: Refactor the timer init code to prepare for GTDT

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Message-ID: <CADyBb7tFaSshUmZsJbNO2tnbqAKEii39NQVfcx5CqDiDsK5OJA@mail.gmail.com>
Date:   Tue, 17 Jan 2017 18:30:04 +0800
From:   Fu Wei <fu.wei@...aro.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        rruigrok@...eaurora.org, "Abdulhamid, Harb" <harba@...eaurora.org>,
        Christopher Covington <cov@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>,
        G Gregory <graeme.gregory@...aro.org>,
        Al Stone <al.stone@...aro.org>, Jon Masters <jcm@...hat.com>,
        Wei Huang <wei@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        Leo Duran <leo.duran@....com>,
        Wim Van Sebroeck <wim@...ana.be>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-watchdog@...r.kernel.org, Tomasz Nowicki <tn@...ihalf.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Julien Grall <julien.grall@....com>
Subject: Re: [PATCH v19 10/15] clocksource/drivers/arm_arch_timer: Refactor
 the timer init code to prepare for GTDT

Hi Mark,

On 17 January 2017 at 02:30, Mark Rutland <mark.rutland@....com> wrote:
> On Wed, Dec 21, 2016 at 02:45:58PM +0800, fu.wei@...aro.org wrote:
>> From: Fu Wei <fu.wei@...aro.org>
>>
>> The patch refactor original memory-mapped timer init code:
>>     (1) Refactor "arch_timer_mem_init", make it become a common code for
>>         memory-mapped timer init.
>>     (2) Add a new function "arch_timer_mem_of_init" for DT init.
>
> As a general note, please write proper commit messages, describing what
> the problem is, and why we are making the changes. These bullet points
> don't add anything to what can be derived from a glance at the code.
>
> For this patch, you can use:
>
>   clocksource: arm_arch_timer: refactor MMIO timer probing
>
>   Currently the code to probe MMIO architected timers mixes DT parsing
>   with actual poking of hardware. This makes the code harder than
>   necessary to understand, and makes it difficult to add support for
>   probing via ACPI.
>
>   This patch factors all the DT-specific logic out of
>   arch_timer_mem_init(), into a new function, arch_timer_mem_of_init().
>   The former pokes the hardware and determines the suitablility of
>   frames based on a datastructure populated by the latter.
>
>   This cleanly separates the two and will make it possible to add
>   probing using the ACPI GTDT in subsequent patches.

Great thanks for this upstream tip.
I have used your example commit message instead.
It will be in v20.

>
> [...]
>
>> +     for_each_available_child_of_node(np, frame_node) {
>> +             int n;
>> +             struct arch_timer_mem_frame *frame = &timer_mem->frame[i];
>> +
>> +             if (of_property_read_u32(frame_node, "frame-number", &n)) {
>> +                     pr_err("Missing frame-number\n");
>> +                     of_node_put(frame_node);
>> +                     goto out;
>> +             }
>> +             frame->frame_nr = n;
>> +
>> +             if (of_address_to_resource(frame_node, 0, &res)) {
>> +                     of_node_put(frame_node);
>> +                     goto out;
>> +             }
>> +             frame->cntbase = res.start;
>> +             frame->size = resource_size(&res);
>> +
>> +             frame->virt_irq = irq_of_parse_and_map(frame_node,
>> +                                                    ARCH_TIMER_VIRT_SPI);
>> +             frame->phys_irq = irq_of_parse_and_map(frame_node,
>> +                                                    ARCH_TIMER_PHYS_SPI);
>>
>> -     if (!arch_timer_needs_of_probing())
>> +             if (++i >= ARCH_TIMER_MEM_MAX_FRAMES)
>> +                     break;
>> +     }
>
> It would be good if we could warn upon seeing more than
> ARCH_TIMER_MEM_MAX_FRAMES children, since that's obviously an error.

OK, NP, will use

if (i >= ARCH_TIMER_MEM_MAX_FRAMES) {
        pr_err(FW_BUG "too many frames, ARMv8 spec only allows 8.\n");
        goto out;
}

at the beginning of this loop.

Here will be replaced by  i++;

Great thanks for your suggestion!

>
> Thanks,
> Mark.



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat