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Re: [PATCH] use rtc_lock to protect RTC operations

To: macro@linux-mips.org
Subject: Re: [PATCH] use rtc_lock to protect RTC operations
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Thu, 03 Nov 2005 22:37:05 +0900 (JST)
Cc: ralf@linux-mips.org, linux-mips@linux-mips.org
In-reply-to: <Pine.LNX.4.55.0511031305280.24109@blysk.ds.pg.gda.pl>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20051103.010115.07642880.anemo@mba.ocn.ne.jp> <20051103125926.GB3149@linux-mips.org> <Pine.LNX.4.55.0511031305280.24109@blysk.ds.pg.gda.pl>
Sender: linux-mips-bounce@linux-mips.org
>>>>> On Thu, 3 Nov 2005 13:15:32 +0000 (GMT), "Maciej W. Rozycki" 
>>>>> <macro@linux-mips.org> said:

>> Unlike on PC CMOS_READ on a DEC is a single read operation, so
>> atomic and so doesn't need to be protected.  I'd have to check the
>> datasheet for any other reason why it might need locking though, so
>> I apply your patch for now and leave this to Maciej for later
>> optimization.

macro>  You are correct -- unless you need to perform multiple RTC
macro> access cycles uninterrupted in a row, a lock is not needed.

Then the dec_rtc_is_updating would be one liner:

        return (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);

What good hardware!

---
Atsushi Nemoto

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