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From: Paul Mackerras <paulus@samba.org>
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Date: Thu, 23 Aug 2001 22:31:20 +1000 (EST)
To: Gabriel Paubert <paubert@iram.es>
Cc: Chris Friesen <cfriesen@nortelnetworks.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] (comments requested) adding finer-grained timing to PPC
  add_timer_randomness()
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Gabriel Paubert writes:

> Reading the PVR is probably faster in this case, since you avoid a
> potential cache miss.

Yep.

> As I said in an earlier message the __USE_RTC macro
> should be made dependent on whether the kernel supports 601 or not.

We don't have USE_RTC in 2.2.  The proposed patch was for 2.2.19.

> No, this is not what they are trying to capture. Furthermore the 7 LSB of
> the decrementer on a 601 are not random (but they don't seem to be 0
> always despite the documentation) so you would have to shift the result

Don't you mean that the 7 LSB of RTCL aren't random and are supposed
to be 0?  The decrementer should decrement by 1 at a rate of 7.8125MHz
and all the bits should be implemented.

Paul.