From mboxrd@z Thu Jan 1 00:00:00 1970 From: megous@megous.com (=?UTF-8?Q?Ond=C5=99ej?= Jirman) Date: Wed, 26 Jul 2017 14:54:40 +0200 Subject: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A regulator to Orange Pi PC In-Reply-To: <20170726114420.ipirqgbluqmggcjy@flea> References: <20170723102749.17323-1-icenowy@aosc.io> <20170723102749.17323-11-icenowy@aosc.io> <25C8A89C-8495-4787-934C-8E9667CD70BF@aosc.io> <82507f40a1ddba8517cf09f51d3afa33@aosc.io> <1501064628.14577.1.camel@megous.com> <20170726114420.ipirqgbluqmggcjy@flea> Message-ID: <1501073680.20056.3.camel@megous.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Maxime Ripard p??e v St 26. 07. 2017 v 13:44 +0200: > Hi, > > On Wed, Jul 26, 2017 at 12:23:48PM +0200, Ond?ej Jirman wrote: > > Hi, > > > > icenowy at aosc.io p??e v St 26. 07. 2017 v 15:36 +0800: > > > > > > > > > > > > > > > Otherwse > > > > > > > > > > > > > + regulator-max-microvolt = <1400000>; > > > > > > > + regulator-ramp-delay = <200>; > > > > > > > > > > > > Is this an actual constraint of the SoC? Or is it a characteristic > > > > > > of the regulator? If it is the latter, it belongs in the driver. > > > > > > AFAIK the regulator supports varying the ramp delay (slew rate). > > > > > > I don't know... > > > > > > Maybe I should ask Ondrej? > > > > It is probably neither. > > > > It is used to calculate a delay inserted by the kernel between setting > > a new target voltage over I2C and changing the frequency of the CPU. > > The actual delay is calculated by the difference between previous and > > the new voltage. > > > > I don't remember seeing anything in the datasheet of the regulator. > > This is just some low value that works. > > > > It would probably be dependent on the capacitance on the output of the > > regulator, actual load (which varies), etc. So it is a board specific > > value. One could measure it with an oscilloscope if there's a need to > > optimize this. > > If this is a reasonable default, then this should be in the > driver. You can't expect anyone to properly calculate a ramp delay and > have access to both a scope and the CPU power lines. It translates to 1ms per 0.2V which is highly conservative. The real times will be in 1-10us range. So I guess this could be a default in the driver. regards, o. > Maxime > > -- > Maxime Ripard, Free Electrons > Embedded Linux and Kernel engineering > http://free-electrons.com > -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: This is a digitally signed message part URL: