linux-kernel - Re: [PATCH] Acer Aspire One Fan Control

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Message-Id: <1240950704.3781.12.camel@maxim-laptop>
Date:	Tue, 28 Apr 2009 23:31:44 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Peter Feuerer <peter@...e.net>
Cc:	petkovbb@...il.com, LKML <linux-kernel@...r.kernel.org>,
	lenb@...nel.org, Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [PATCH] Acer Aspire One Fan Control

On Tue, 2009-04-28 at 22:17 +0200, Peter Feuerer wrote:
> Hi Maxim,
> 
> >> Their N270 datasheet
> >> (http://download.intel.com/design/processor/datashts/320032.pdf) talks
> >> about max Tj (junction temperature) being 90°C for a TDP of 2.5W and if
> >> you operate below that limit "functionality and long-term reliability
> >> can be expected." :)
> >> 
> >> There's also an internal termtrip sensor which is designed to go off at
> >> Tj=125°C so, yeah, I guess something 70°C should be ok.
> > 
> > I have small note:
> > 
> > So yes cpu can withstand 90 C, but will rest of the motherboard?
> > 
> > (Most other cpus are rated at 60C)
> 
> That's why the module is started in "user mode" where the bios controls the 
> fan. - The Bios just starts the fan as soon as the temperature is higher 
> than 40 degree celsius.
> 
> The user must explicitely start "kernel mode" to make the kernel 
> controlling the fan. Maybe we should add a warning somewhere, that it could 
> harm the hardware?
Then its fine.

(I probably won't turn fan off though).

I have a aspire one, so I install this driver.
one more note thought, you might want to rename it to something else,
or maybe merge with acer-wmi?

If I understand correctly, this driver also provides temperature
reading, which is in my opinion very nice.
Thus, this seems more a 'acer aspire extras'

Or, maybe even better, maybe you can name it a 'EC extra driver', since
today many notebooks are controlled via EC, and thus you or other
contributors might add more features to this driver.
How about a EC register dump for example in /sys, so users could look at
EC registers comfortably

But of course, I think this driver should first be merged.

Another small note, is would be very nice to have a locking mechanism
for EC reads/writes, so there would be no conflicts between accesses.

For example my main notebook, acer 5720, has semi broken fan control
(they broke it in newer bioses, but I have to use them, because fan
won't work at all in 64-bit OS I use (linux of course).

There is a way to control the fan, by writing fake temperatures to EC
and doing that very often, since I think SMI writes there too.
But when I do so, ofnen other EC related things fail, like brightness
control for example. I think this is due to the fact that acer_ec does
direct I/O.

so I would like to see a interface to read/write EC properly.

Best regards, and thanks,
	Maxim Levitsky

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