Hello, We recently reverse engineered PWM-based voltage management but found an odity in the input clock frequency for the PWM controller. It seems like RM is assuming an input clock of 27.648 MHz instead of the actual 27MHz crystal found on the board. I thus have the following questions: - Is it a fixed value hardcoded in RM? (Current way it is done in Nouveau) - Should we use crystal_MHz * 1.024? I could spend some time hooking up my osciloscope to the VR to check if it is a bringup issue but it would not help Nouveau much as we need to reproduce the behaviour of RM anyway since this is the only validated configuration. Thanks in advance, Martin PS: The registers for this PWM controller are 0x20340 and 0x20344.
Thanks, Martin. I'll try to follow up on this next week and get you an answer. What GPUs have you observed this on? On Fri, Sep 18, 2015 at 11:13:53PM +0300, Martin Peres wrote:> Hello, > > We recently reverse engineered PWM-based voltage management but found an > odity in the input clock frequency for the PWM controller. It seems like RM > is assuming an input clock of 27.648 MHz instead of the actual 27MHz crystal > found on the board. > > I thus have the following questions: > - Is it a fixed value hardcoded in RM? (Current way it is done in Nouveau) > - Should we use crystal_MHz * 1.024? > > I could spend some time hooking up my osciloscope to the VR to check if it > is a bringup issue but it would not help Nouveau much as we need to > reproduce the behaviour of RM anyway since this is the only validated > configuration. > > Thanks in advance, > Martin > > PS: The registers for this PWM controller are 0x20340 and 0x20344.
On 18/09/15 23:30, Andy Ritger wrote:> Thanks, Martin. I'll try to follow up on this next week and get you an answer. What GPUs have you observed this on? >Thanks Andy, As far as I can tell, it is the case for all GPUs using the PWM-based voltage management. To be more specific, we have seen this behaviour on a GK106 (mobile), a GM117 and a GM204.