On Wednesday, June 11, 2008 7:53 am Jean Delvare wrote: > Hi Jesse, hi Krzysztof, > > On Tue, 10 Jun 2008 12:02:19 -0700, Jesse Barnes wrote: > > On Sunday, June 08, 2008 4:47 am Krzysztof Helt wrote: > > > From: Krzysztof Helt <krzysztof.h1@xxxxx> > > > > > > This patch unhides the SMBus on Compaq Deskpro EN > > > SFF P667 with the Intel 815E chipset. Unhiding it reveals > > > a THMC51 hardware monitoring chip. > > > > > > Jean Delvare has checked that this machine has no ACPI > > > magic touching the SMBus nor the hardware monitoring chip, > > > so this should be safe. > > Let it be noted that ACPI is only one of the possible offenders. SMM is > another one. The user reported that his fan speed was changing speeds so > something has to be acting upon temperature changes. This could be the > fan itself, or this could be SMM code changing the registers of the > chip. > > At this point of the investigation, I am still not 100% sure that the > patch is safe. I'd say it is only safe if the user's fan is actually > self-regulated based on the temperature. > > One easy way to test would be to verify what happens when the > temperature exceeds 53 degrees C (the high temperature limit) and 78 > degrees C (the critical temperature limit). Typical SMM code would > change the high and low limits when the high limit is crossed, this > should be clearly visible in the output of "sensors". > > BTW, Krzysztof, what about adding (read-only) support for the critical > limits to your thmc50 driver? It would be helpful in a situation like > this. > > Another thing to check is whether the value of register 0x19 (analog > output) changes automatically when the fan speeds up. > > Until these tests are done, I consider this patch possibly unsafe and > not ready to go to Linus (although probably OK for -next). Ok, thanks for the heads up Jean, I'll keep this one out of the queue I send to Linus until we get confirmation about its safety. Thanks, Jesse -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
