linux-kernel - Re: [PATCH v2 25/35] nds32: Build infrastructure

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Date:   Wed, 29 Nov 2017 19:39:58 +0800
From:   Greentime Hu <green.hu@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        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" <linux-serial@...r.kernel.org>,
        Vincent Chen <vincentc@...estech.com>
Subject: Re: [PATCH v2 25/35] nds32: Build infrastructure

2017-11-29 17:25 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
> On Wed, Nov 29, 2017 at 10:10 AM, Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
>> Hi Arnd,
>>
>> On Wed, Nov 29, 2017 at 9:58 AM, Arnd Bergmann <arnd@...db.de> wrote:
>>> On Wed, Nov 29, 2017 at 9:39 AM, Greentime Hu <green.hu@...il.com> wrote:
>>>> 2017-11-27 22:21 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
>>>>> On Mon, Nov 27, 2017 at 1:28 PM, Greentime Hu <green.hu@...il.com> wrote:
>>>>>> diff --git a/arch/nds32/Kconfig.cpu b/arch/nds32/Kconfig.cpu
>>>>>> +config CPU_CACHE_NONALIASING
>>>>>> +       bool "Non-aliasing cache"
>>>>>> +       help
>>>>>> +         If this CPU is using VIPT data cache and its cache way size is larger
>>>>>> +         than page size, say N. If it is using PIPT data cache, say Y.
>>>>>> +
>>>>>> +         If unsure, say Y.
>>>>>
>>>>> Can you determine this from the CPU type?
>>>>
>>>> There is no cpu register to determine it. It also depeneds on page
>>>> size and way size however page size is configurable by software.
>>>> These codes are determined at compile time will be benefit to code
>>>> size and performance.
>>>> IMHO, I think it would be better to be determined here.
>>>
>>> I meant determining it at compile time from other Kconfig symbols,
>>> if that's possible. Do the CPU cores each have a fixed way-size?
>>> If they do, it could be done like
>>>
>>> menu "CPU selection"
>>>
>>> config CPU_N15
>>>       bool "AndesCore N15"
>>>       select CPU_CACHE_NONALIASING
>>>
>>> config CPU_N13
>>>       bool "AndesCore N15"
>>>       select CPU_CACHE_NONALIASING if PAGE_SIZE_16K
>>>
>>> ...
>>>
>>> endmenu
>>>
>>> and then you can use the same CPU_... symbols to make other decisions
>>> as well, e.g. CPU specific compiler optimizations.
>>
>> Do you want to support multiple CPU types in a single kernel image
>> (I see no "choice" statement above)?
>> If yes, you may have a mix of aliasing and non-aliasing caches, so
>> you may want to invert the logic, and select CPU_CACHE_ALIASING
>> instead.
>
> Right, my mistake.
>

Thanks to Arnd and Geert!

How about this?

choice
        prompt "CPU type"
        default CPU_N13
config CPU_N15
        bool "AndesCore N15"
        select CPU_CACHE_NONALIASING
config CPU_N13
        bool "AndesCore N13"
        select CPU_CACHE_NONALIASING if ANDES_PAGE_SIZE_8KB
config CPU_N10
        bool "AndesCore N10"
        select CPU_CACHE_NONALIASING if ANDES_PAGE_SIZE_8KB
config CPU_D15
        bool "AndesCore D15"
        select CPU_CACHE_NONALIASING
        select HWZOL
config CPU_D10
        bool "AndesCore D10"
        select CPU_CACHE_NONALIASING if ANDES_PAGE_SIZE_8KB
endchoice