Messages in this thread | | | Date | Tue, 1 Mar 2016 09:18:46 +0530 | From | Laxman Dewangan <> | Subject | Re: [PATCH 1/2] regulator: DT: Add support to scale ramp delay based on platform behavior |
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On Tuesday 01 March 2016 07:53 AM, Mark Brown wrote: > * PGP Signed by an unknown key > > On Mon, Feb 29, 2016 at 09:47:51AM -0800, Bjorn Andersson wrote: >> On Mon 29 Feb 06:40 PST 2016, Laxman Dewangan wrote: >>> It is observed that voltage change in given rail affected by the load >>> and the capacitor in the rail. This may cause the slow ramp in voltage >>> against what PMIC has programmed. >> The regulator-ramp-delay is a variable you can tweak on a board basis, >> so I'm not sure what benefit it gives to be able to add a scaling >> factor to this. >> In my experience your HW engineer will say "you have to wait X ms", not >> "you have to wait 125% of X ms". >> Can you please elaborate on why the original knob isn't sufficient? > Right, this definitely feels like the wrong thing is being specified > here (and also like the PMIC might be going out of spec, possibly as a > result of being overloaded) and that the existing board specific > controls should be used. It just doesn't correspond to the way people > usually talk about specs for PMICs. >
Most of PMICs offer to configure the slew rate (ramp time). For discussion, I am considering MAX77620 LDOs provides option to 27mV/us and 100mV/us.
HW team characterize the board and its rail and come up with the following data: - Configure PMIC to 27mV/us for ramp time. - With this measured value of ramp on board is 10mV/us and it is safe to assume 5mv/us to consider the board variations.
So we have now two input from HW team: 1. What should be configure in PMIC. 2. And for calculation, how much ramp need to be consider.
For (1), it is 25mV/us and for (2) which 540% (27 *100/5).
Currently, we can provide the 27mv/us as ramp-delay but do not have option for scaling it.
My patch add for knob for (2).
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