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Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register support

From Andy Shevchenko <andy.shevchenko@gmail.com>
Newsgroups linux.kernel
Subject Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register support
Date 2017-05-17 12:00 +0200
Message-ID <tI3Um-1pv-33@gated-at.bofh.it> (permalink)
References <tHoo9-lZ-13@gated-at.bofh.it> <tHIGf-4Ub-17@gated-at.bofh.it> <tHXYC-6cB-5@gated-at.bofh.it> <tHZQJ-7s4-3@gated-at.bofh.it> <tI00p-7v7-23@gated-at.bofh.it>
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On Wed, May 17, 2017 at 8:43 AM, Dong Aisheng <dongas86@gmail.com> wrote:
> On Wed, May 17, 2017 at 08:37:41AM +0300, Nikita Yushchenko wrote:
>>
>>
>> 17.05.2017 06:39, Dong Aisheng wrote:
>> > On Tue, May 16, 2017 at 02:15:08PM +0300, Nikita Yushchenko wrote:
>> >>>  static u32 lpuart32_read(void __iomem *addr)
>> >>>  {
>> >>> - return ioread32be(addr);
>> >>> + return lpuart_is_be ? ioread32be(addr) : readl(addr);
>> >>>  }
>> >>>
>> >>>  static void lpuart32_write(u32 val, void __iomem *addr)
>> >>>  {
>> >>> - iowrite32be(val, addr);
>> >>> + if (lpuart_is_be)
>> >>> +         iowrite32be(val, addr);
>> >>> + else
>> >>> +         writel(val, addr);
>> >>>  }
>> >>
>> >> What if this is ever executed on big endian system?
>> >>
>> >
>> > Sorry, not catching the point...
>> >
>> > What issues will meet?
>>
>> Isn't writel() in host endian?
>
> On big endian systems, it is supposed to run iowrite32be.

It looks like you substituting *bus* side with CPU *side* of communication.

If you are talking about CPU side
__raw_readl() / __raw_writel() will do the trick.

-- 
With Best Regards,
Andy Shevchenko

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Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register  support Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-05-16 13:20 +0200
  Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register  support Dong Aisheng <dongas86@gmail.com> - 2017-05-17 05:40 +0200
    Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register  support Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-05-17 07:40 +0200
      Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register  support Dong Aisheng <dongas86@gmail.com> - 2017-05-17 07:50 +0200
        Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register  support Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-05-17 08:00 +0200
          Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register  support Dong Aisheng <dongas86@gmail.com> - 2017-05-17 08:20 +0200
        Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register support Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-05-17 12:00 +0200
  Re: [V2, 2/6] tty: serial: lpuart: add little endian 32 bit register support Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-05-17 12:00 +0200

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