linux-kernel - Re: [PATCH v6 06/36] nds32: Kernel booting and initialization

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Message-ID: <CAEbi=3dJm=M-1UjUftb5qb0YOOsq92zzF86xeaVOhzULjvT3eA@mail.gmail.com>
Date:   Sat, 20 Jan 2018 00:34:38 +0800
From:   Greentime Hu <green.hu@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Greentime <greentime@...estech.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        Vincent Chen <deanbo422@...il.com>,
        DTML <devicetree@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-serial@...r.kernel.org,
        Geert Uytterhoeven <geert.uytterhoeven@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>, Greg KH <greg@...ah.com>,
        Guo Ren <ren_guo@...ky.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        David Miller <davem@...emloft.net>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        Vincent Chen <vincentc@...estech.com>
Subject: Re: [PATCH v6 06/36] nds32: Kernel booting and initialization

Hi, Arnd:

2018-01-18 18:11 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
> On Mon, Jan 15, 2018 at 6:53 AM, Greentime Hu <green.hu@...il.com> wrote:
>
> I had not looked at this patch in enough detail earlier, sorry about
> that. It should be
> easy enough to fix though.
>
>> +#ifdef CONFIG_VGA_CONSOLE
>> +struct screen_info screen_info;
>> +#endif
>
> I would assume that you can't ever have a VGA console. Just drop all
> the references
> here and instead send a patch to the fbdev maintainer to add the dependency
> at CONFIG_VGA_CONSOLE to prevent selecting it with nds32.

I found it can be built pass for now because we disable it in defconfig.
Should I send the patch in v7 series?

>> +
>> +extern void __init early_init_devtree(void *params);
>> +extern void __init early_trap_init(void);
>
> similarly, these are declared in include/linux/of_fdt.h
>

early_trap_init is a nds32 function. I will move it to nds32.h

>> +void __init setup_arch(char **cmdline_p)
>> +{
>> +       early_init_devtree(__atags_pointer ?
>> +                          phys_to_virt(__atags_pointer) : __dtb_start);
>
> The reference to '__atags_pointer' appears to be a leftover from pre-DT
> days. Can you just remove that?

Yes, I will remove it.

>> +void calibrate_delay(void)
>> +{
>> +       const int *val;
>> +       struct device_node *cpu = NULL;
>> +       cpu = of_find_compatible_node(NULL, NULL, "andestech,nds32v3");
>> +       val = of_get_property(cpu, "clock-frequency", NULL);
>> +       if (!val || !*val)
>> +               panic("no cpu 'clock-frequency' parameter in device tree");
>> +       loops_per_jiffy = be32_to_cpup(val) / HZ;
>> +       pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
>> +               loops_per_jiffy / (500000 / HZ),
>> +               (loops_per_jiffy / (5000 / HZ)) % 100, loops_per_jiffy);
>> +}
>
> This seems very odd to me: The 'clock-frequency' property in the
> cpu node should refer to the actual frequency it is running at, but that
> tends to be different from the bogomips as needed by the ndelay()
> function. Can you explain what is going on here?
>

This implementation is referenced from openrisc.
https://lkml.org/lkml/2017/11/17/228



Thank you.