Message-ID: <4ACEAAF5.90304@rtr.ca>
Date: Thu, 08 Oct 2009 23:16:05 -0400
From: Mark Lord <liml@rtr.ca>
Organization: Real-Time Remedies Inc.
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To: Bernie Innocenti <bernie@codewiz.org>
Cc: Harri Olin <harri.olin@gmail.com>, linux-ide@vger.kernel.org,
       lkml <linux-kernel@vger.kernel.org>, sysadmin <sysadmin@gnu.org>
Subject: Re: sata_mv 0000:03:06.0: PCI ERROR; PCI IRQ cause=0x30000040
References: <1254546642.1438.135.camel@giskard> <4ACA6904.1060509@rtr.ca>	 <4ACB3741.2030101@gmail.com> <1254852272.1471.172.camel@giskard>	 <4ACBA33C.7090606@rtr.ca>  <1254873978.1471.463.camel@giskard>	 <1254879618.1471.525.camel@giskard>  <4ACC076F.7020000@rtr.ca> <1255020134.30440.698.camel@giskard> <4ACEA8FB.4060901@rtr.ca>
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Mark Lord wrote:
> Bernie Innocenti wrote:
>>
>> I want to try reducing the frequency of the PCI-X bus, but the BIOS does
>> not seem to provide a setting for it.  Is there another way?
> ..
> 
> Nothing that's easy.
..

Adding to that:  there is a register on the chip,
which software could use to override the normal auto-detected
PCI mode (bus speed) for the chip.  This could be used to,
say, select 100Mhz or 66Mhz, or even 33Mhz operation.

BUT.. the register is autodetected from the bus at power-on,
and so if software wants to override that (by rewriting the reg),
it will also need to reset the PCI bus afterward.

Which requires knowing how to reset a PCI bridge,
something I don't know about.

Cheers
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