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Date: Wed, 26 Feb 2003 12:46:50 -0800
From: "Randy.Dunlap" <rddunlap@osdl.org>
To: root@chaos.analogic.com
Cc: rusty@linux.co.intel.com, alan@lxorguk.ukuu.org.uk, p_gortmaker@yahoo.com,
       linux-kernel@vger.kernel.org
Subject: Re: [2.5.63 PATCH][TRIVIAL]Change rtc.c ioport extend from 10h to 8h
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On Wed, 26 Feb 2003 15:29:06 -0500 (EST)
"Richard B. Johnson" <root@chaos.analogic.com> wrote:

| On 26 Feb 2003, Rusty Lynch wrote:
| 
| > On Wed, 2003-02-26 at 11:35, Richard B. Johnson wrote:
| > > On 26 Feb 2003, Rusty Lynch wrote:
| > > 
| > > > The real time clock only needs 8 bytes, but rtc.c is reserving 10h bytes.
| > > [SNIPPED...]
| > > 
| > > It only needs two bytes port 0x70 and port 0x71 in ix86. Since the Sparc
| > > gets addressed differently and can only read/write words, it needs 8
| > > bytes.  Please, if you are going to fix it, please fix it only once by
| > > setting a different length for the different machines!
| > > Cheers,
| > > Dick Johnson
| > 
| > Actually, it's finer grain then x86, it's a chipset issue.  As Randy
| > pointed out in the original thread ==>
| > > Some Intel chipset specs list RTC as using 0x70 - 0x77, probably with
| > > some aliasing in there, so it looks to me like an EXTENT of 8 would be
| > > safer and still allow you access to 0x79.
| > > 
| > > I'm looking at 82801BA-ICH2, 82801-ICH3, and 82801AA-ICH0 specs.
| > > 
| > > -- 
| 
| Can't see what an IDE chip-set has to do with it. The RTC can only
| be accessed as an offset-location and a data-location. You write
| an offset at one location and you read/write data at another location.
| On an ix86, the locations are adjacent byte-wide ports. On the Sparc
| they are adjacent dword-wide memory locations.

IDE is just 1 of about 20 functional units in those chipsets.
The chipset specs say that there are some other RTC registers there
(total of 8).
Reducing the RTC I/O space from 16 to 8 bytes looks right to me,
even on x86.

| Cheers,
--
~Randy
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