linux-kernel - Re: [PATCH v10 2/5] rtc: goldfish: introduce goldfish_ioread32()/goldfish

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Message-ID: <64d4b52f-cb5b-2024-e7f9-7a5babc62170@vivier.eu>
Date:   Wed, 19 Jan 2022 10:11:28 +0100
From:   Laurent Vivier <laurent@...ier.eu>
To:     Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        John Stultz <john.stultz@...aro.org>,
        linux-rtc@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH v10 2/5] rtc: goldfish: introduce
 goldfish_ioread32()/goldfish_iowrite32()

Le 19/01/2022 à 09:49, Arnd Bergmann a écrit :
> On Wed, Jan 19, 2022 at 9:21 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>> On Wed, Jan 19, 2022 at 1:05 AM Laurent Vivier <laurent@...ier.eu> wrote:
>>
>> I've just discovered include/linux/goldfish.h, which already has gf_*()
>> accessors for 64-bit, so it'd make sense to move the above there,
>> and adjust the names.
> 
> Yes, good idea.

So the idea is to put goldfish accessors inside a "#ifdef CONFIG_M68K ... #else ... #endif" in 
include/linux/goldfish.h and not in generic-asm/io.h for the generic version and 
m68k/include/ams/io.h for the m68k version?

> 
>>
>> Arnd: note that the existing ones do use __raw_writel().
> 
> It looks like Laurent introduced that bug in da31de35cd2f ("tty: goldfish: use
> __raw_writel()/__raw_readl()") and could fix it up here. Laurent, was the intent

The idea was to use the native endianness of the CPU, I missed it can differ from the one of the 
architecture.

> of this earlier patch also to make the driver usabel for m68k, or are there
> any other targets you looked at that had mixed up endianness?
> 

Yes, the intent was to make it usable for m68k.
I think all the targets that use goldfish are little-endian, it's why there was no problem until now.

Let me know which solution you prefer, I will update the series accordingly.

Thanks,
Laurent