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Re: [PATCH] arc: use little endian accesses

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On Thursday 10 March 2016, Vineet Gupta wrote:
> On Wednesday 09 March 2016 10:51 PM, Lada Trimasova wrote:
> > Memory access primitives should use cpu_to_le16, cpu_to_le32, le16_to_cpu
> > and le32_to_cpu because it is not really guaranteed that drivers handles
> > any ordering themselves.
> 
> That is the driver issue. readxx as API simply returns data in native endianness.
> We've had EZChip running big endian and so far and they didn't need this change.

Most drivers using readl() or readl_relaxed() expect those to perform byte
swaps on big-endian architectures, as the registers tend to be fixed endian,
so the change seems reasonable.

It depends a little bit on how endian mode is implemented in the CPU: do you
follow the normal model of swapping byte order in the load/store instructions
of the CPU when running big-endian, or is the CPU always running little-endian
but the bus addresses get mangled on byte accesses to give the illusion
of a big-endian system?

	Arnd

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Thread

[PATCH] arc: use little endian accesses Lada Trimasova <Lada.Trimasova@synopsys.com> - 2016-03-09 18:30 +0100
  Re: [PATCH] arc: use little endian accesses Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-10 06:10 +0100
    Re: [PATCH] arc: use little endian accesses Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-10 06:30 +0100
    Re: [PATCH] arc: use little endian accesses Arnd Bergmann <arnd@arndb.de> - 2016-03-10 08:50 +0100
      Re: [PATCH] arc: use little endian accesses Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-11 06:20 +0100
    Re: [PATCH] arc: use little endian accesses Alexey Brodkin <Alexey.Brodkin@synopsys.com> - 2016-03-10 08:50 +0100
      Re: [PATCH] arc: use little endian accesses Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-10 11:00 +0100
        Re: [PATCH] arc: use little endian accesses Lada Trimasova <Lada.Trimasova@synopsys.com> - 2016-03-10 20:00 +0100
          Re: [PATCH] arc: use little endian accesses Arnd Bergmann <arnd@arndb.de> - 2016-03-10 20:30 +0100
            Re: [PATCH] arc: use little endian accesses Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-11 13:50 +0100
              Re: [PATCH] arc: use little endian accesses Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2016-03-12 05:30 +0100
          Re: [PATCH] arc: use little endian accesses Noam Camus <noamca@mellanox.com> - 2016-03-11 06:30 +0100

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