Re: [linux-sunxi] Re: [PATCH 52/54] arm64: dts: allwinner: Remove regulator-ramp-delay

Icenowy Zheng
2021-08-06T12:12:02Z

于 2021年8月6日 GMT+08:00 下午8:05:56, Chen-Yu Tsai <wens@csie.org> 写到:
>On Fri, Aug 6, 2021 at 7:49 PM Icenowy Zheng <icenowy@aosc.io> wrote:
>>
>> 在 2021-07-22星期四的 10:16 +0200，Maxime Ripard写道：
>> > On Thu, Jul 22, 2021 at 12:55:53AM -0500, Samuel Holland wrote:
>> > > On 7/21/21 9:04 AM, Maxime Ripard wrote:
>> > > > The regulator-ramp-delay property isn't documented in the binding
>> > > > for
>> > > > the AXP806, and it's ignored by the driver. Remove those
>> > > > properties.
>> > >
>> > > This is a generic regulator property, parsed by
>> > > of_get_regulation_constraints, which is called by
>> > > regulator_of_get_init_data in the regulator core. And it appears in
>> > > bindings/regulator/regulator.yaml. I believe the binding needs to be
>> > > fixed, not the device trees.
>> >
>> > It's indeed parsed by the regulator framework, but then it calls into
>> > the driver if that property is set using set_ramp_delay if it's set.
>>
>> Not only is it used for set_ramp_delay, but it's also used to calculate
>> a post-change delay, see the following position (it can be overrided by
>> a custom set_voltage_time in the driver):
>>
>> https://elixir.bootlin.com/linux/latest/source/drivers/regulator/core.c#L3339
>
>Having just dug through the regulator core code at work, I agree.
>
>Furthermore, the commit log for this addition specifically mentions the
>reason for adding this property is to provide a (guessed) ramp rate for
>the core to do a proper delay for the regulator to ramp up, not to set
>the actual ramp rate in hardware.

Well we must agree that we have some more suitable property that delays
for a constant span, see lines below in the function I mentioned.

>
>
>ChenYu
>
>
>[1] https://git.kernel.org/torvalds/c/fe79ea577be81e1e71642826ab00e676dc59c194
>
>> >
>> > https://elixir.bootlin.com/linux/latest/source/drivers/regulator/core.c#L1378
>> >
>> > We don't set that hook for the AXP806 DCDC-A and DCDC-E regulators
>> > (that
>> > use AXP_DESC_RANGES) at all:
>> >
>> > https://elixir.bootlin.com/linux/latest/source/drivers/regulator/axp20x-regulator.c#L343
>> >
>> > And the only implementation we have (set for AXP_DESC and AXP_DESC_IO)
>> > works only for the AXP209:
>> >
>> > https://elixir.bootlin.com/linux/latest/source/drivers/regulator/axp20x-regulator.c#L368
>> >
>> > So, it just looks like those properties have never been tested since
>> > they were just ignored.
>> >
>> > Maxime
>> >
>>
>> --
>> You received this message because you are subscribed to the Google Groups "linux-sunxi" group.
>> To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscribe@googlegroups.com.
>> To view this discussion on the web, visit https://groups.google.com/d/msgid/linux-sunxi/68e4820ead3107aa4e80dcaf9243bd11de5fce98.camel%40aosc.io.