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Subject: Re: svn commit: r299364 -
 head/sys/compat/linuxkpi/common/include/linux
To: cem@FreeBSD.org, Matthew Macy <mmacy@nextbsd.org>
References: <201605101204.u4AC4vhR007264@repo.freebsd.org>
 <CAG6CVpUX399fRcLod5UVgrds_xCYdD5KwDzw5WhWKtzGcQTwkw@mail.gmail.com>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
From: Hans Petter Selasky <hps@selasky.org>
Message-ID: <072816bb-716e-4164-0cde-2febf8bd1866@selasky.org>
Date: Tue, 10 May 2016 19:10:12 +0200
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On 05/10/16 16:49, Conrad Meyer wrote:
> On Tue, May 10, 2016 at 5:04 AM, Hans Petter Selasky
> <hselasky@freebsd.org> wrote:
>> Author: hselasky
>> Date: Tue May 10 12:04:57 2016
>> New Revision: 299364
>> URL: https://svnweb.freebsd.org/changeset/base/299364
>>
>> Log:
>>   Add more LinuxKPI I/O functions.
>>
>>   Obtained from:        kmacy @
>> ...
>> @@ -166,5 +212,35 @@ __iowrite64_copy(void *to, void *from, s
>>  #endif
>>  }
>>
>> +enum {
>> +       MEMREMAP_WB = 1 << 0,
>> +       MEMREMAP_WT = 1 << 1,
>> +       MEMREMAP_WC = 1 << 2,
>> +};
>> +
>> +static inline void *
>> +memremap(resource_size_t offset, size_t size, unsigned long flags)
>> +{
>> +       void *addr = NULL;
>> +
>> +       if ((flags & MEMREMAP_WB) &&
>> +           (addr = ioremap_wb(offset, size)) != NULL)
>> +               goto done;
>> +       if ((flags & MEMREMAP_WT) &&
>> +           (addr = ioremap_nocache(offset, size)) != NULL)
>> +               goto done;
>
> x86 can actually map memory as WT rather than UC.  Why throw that away?
>
>> +       if ((flags & MEMREMAP_WC) &&
>> +           (addr = ioremap_wc(offset, size)) != NULL)
>> +               goto done;
>> +done:
>> +       return (addr);
>> +}
>> +
>> ...

Hi Conrad,

I agree. I see no reason to not implement ioremap_wt() for x86 (32-bit 
and 64-bit) and use it for the WT case.

--HPS