On 28/11/17 07:32, John Hubbard wrote: > On 11/23/2017 02:48 PM, Martin Peres wrote: >> On 23/11/17 10:06, John Hubbard wrote: >>> On 11/22/2017 05:07 PM, Martin Peres wrote: >>>> Hey, >>>> >>>> Thanks for your answer, Andy! >>>> >>>> On 22/11/17 04:06, Ilia Mirkin wrote: >>>>> On Tue, Nov 21, 2017 at 8:29 PM, Andy Ritger <arit...@nvidia.com> wrote: >>>>> Martin's question was very long, but it boils down to this: >>>>> >>>>> How do we compute the correct values to write into the e114/e118 pwm >>>>> registers based on the VBIOS contents and current state of the board >>>>> (like temperature). >>>> >>>> Unfortunately, it can also be the e11c/e120 couple, or 0x200d8/dc on >>>> GF119+, or 0x200cd/d0 on Kepler+. >>>> >>>> At least, it looks like we know which PWM controler we need to drive, so >>>> I did not want to muddy the water even more by giving register >>>> addresses, rather concentrating on the problem at hand: How to compute >>>> the duty value for the PWM controler. >>>> >>>>> >>>>> We generally do this right, but appear to get it extra-wrong for certain >>>>> GPUs. >>>> >>>> Yes... So far, we are always safe, but users tend to mind when their >>>> computer sound like a jumbo jet at take off... Who would have thought? :D >>>> >>>> Anyway, looking forward to your answer! >>>> >>>> Cheers, >>>> Martin >>> >>> >>> Hi Martin, >>> >>> One of our firmware engineers thinks that this looks a lot like PWM >>> inversion. >>> For some SKUs, the interpretation of the PWM duty cycle is inverted. That >>> would probably make it *very* difficult to find a sensible algorithm that >>> covered all the SKUs, given that some are inverted and others are not. >>> >>> For the noisy GPUs, a very useful experiment would be to try inverting it, >>> like this: >>> >>> pwmDutyCycle = pwmPeriod - pwmDutyCycle; >>> >>> ...and then see if fan control starts behaving closer to how you've >>> actually >>> programmed it. >>> >>> Would that be easy enough to try out? It should help narrow down the >>> problem at least. >>> >> >> Hey John, >> >> Unfortunately, we know about PWM inversion, and one can know which mode >> to use based on the GPIO entry associated to the fan (inverted). We have >> had support for this in Nouveau for a long time. At the very least, this >> is not the problem on my GF108. >> >> I am certain that the problem I am seeing is related to this vbios table >> I wrote about (BIT P, offset 0x18). It is used to compute what PWM duty >> I should use for both 0 and 100% of the fan speed. >> >> Computing the value for 0% fan speed is difficult because of >> non-continuous nature of some of the functions[1], but I can always >> over-approximate. However, I failed to accurately compute the duty I >> need to write to get the 100% fan speed (I have cases where I greatly >> over-estimate it...). >> >> Could you please check out the vbios table I am pointing at? I am quite >> sure that your documentation will be clearer than my babbling :D > > Yes. We will check on this. There has been some productive discussion > internally, but it will take some more investigation. > > thanks, > John Hubbard
Have the productive discussions panned out? Thanks in advance, Martin _______________________________________________ Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau
