From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?iso-8859-1?Q?Bj=F6rn_Gerhart?= Date: Thu, 29 Mar 2012 19:46:11 +0000 Subject: Re: [lm-sensors] [PATCH] hwmon: (it87) Add support for IT8781F, IT8782F, IT8783E/F Message-Id: <59C1832D-DAB3-4EE0-9781-32AE23035B35@extracloud.de> List-Id: References: <6.2.5.6.2.20120324091434.02773d68@roeck-us.net> In-Reply-To: <6.2.5.6.2.20120324091434.02773d68@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: lm-sensors@vger.kernel.org Hi Guenter, Am 28.03.2012 um 01:28 schrieb Guenter Roeck: > On Tue, Mar 27, 2012 at 03:21:35PM -0400, Bj=F6rn Gerhart wrote: >> Hi Jean, >>=20 >> Am 26.03.2012 um 19:01 schrieb Jean Delvare: >>> [..] >>>> If actually it is the job of the module to do such calculations, I wou= ld offer to create an it87 patch for IT8783 fixing this - analog to an exis= ting module with a similar behavior (if you know one). >>>=20 >>> You assume that the PECI value always refers to the CPU. I do not think >>> this is true, other parts (e.g. north bridge) could report their >>> temperature through PECI as well. >>>=20 >>> And if it is the CPU temperature, we already have the coretemp driver >>> providing the same information, so there's little point in implementing >>> the same in it87. The only benefit of handling PECI sensors in it87 and >>> the like would be so that they can be used as sources for automatic fan >>> speed control, but if the chip itself has no idea about the absolute >>> value of the temperature then I doubt it can use it for automatic fan >>> speed control. >>>=20 >> Yes, with the coretemp driver even both core temperatures are displayed = correctly. So I agree, it's nonsense to implement our special design into t= he generic driver ;-) >=20 > Depends. As Jean mentioned, it would make sense if the temperature can be= used for > automatic fan control. >=20 That's right, for instance the BIOS on our mainboard controls the fan RPM t= hrough that PECI value. > The PECI specification says (I qoute Wikipedia) "PECI reports a negative = value expressing > the difference between the current temperature and the thermal throttle p= oint (at which > the CPU reduces speed or shuts down to prevent damage due to overheating)= instead of the > absolute temperature". So the negative value and slope is to be expected. >=20 > Question is if there is a way to tell the chip the how to calculate the r= eal temperature > from the raw value reported by PECI. The Nuvoton chips have a set of regi= sters for that > purpose. >=20 > Since the raw PECI value is not very useful, it might well be that it is = possible > to program the ITE chip to adust its readings. No idea how to do that, th= ough. > If your HW folks have a contact at ITE, maybe you could ask them to try t= o find out. > Or maybe there is some BIOS code available from ITE and/or from BIOS vend= ors. >=20 My HW colleagues don't have deeper knowledge about PECI. I'll try to get th= e ITE contact address to ask ITE directly.. As far as I know, our BIOS simply uses the intel CPU register to calculate = the real temperature. > Alternatively, it might be possible to program fan control to take the ne= gative slope > into account; at least Wikipedia suggests that as possibility (to have th= e fan run faster > as the reported temperature approaches zero from below). No idea how to d= o that either, > though. >=20 > There is also register 0x0a, bits 4-6. Is that set to PECI on your board ? >=20 Yes, in our design on Index Register 0x0A, bits 6-4 are set to 110, which a= lso means that PECI is enabled. However, on our mainboard we have PECI mode enabled but at the same time we= can use UART6. There is a trick to disable the parallel port and therefore= enable COM6 on the parallel port's pins: When PECI mode is enabled, UART6 is not necessarily disabled. It depends on= the wiring. When JP4 (pin 1) is set to 0, the parallel port on pins 100..1= 06 gets disabled. Therefore, on these pins UART6 can be used instead (see c= hapter "Power On Strapping Options"). Bj=F6rn _______________________________________________ lm-sensors mailing list lm-sensors@lm-sensors.org http://lists.lm-sensors.org/mailman/listinfo/lm-sensors