Re: [PATCH v2 06/12] mmc: pwrseq: add support for power-on sequencing through DT

[Caesar Wang]

Hi Javier,

å 2016å01æ12æ 00:02, Javier Martinez Canillas åé:
> Hello Heiko,
>
> On 01/08/2016 11:42 PM, Heiko Stuebner wrote:
> > Am Freitag, 8. Januar 2016, 09:22:31 schrieb Javier Martinez Canillas:
> > > > For example:
> > > > we need enable wifi module power to via the WL_REG_ON
> > > > pin, we need enable it as the regulator if this pin is connected to
> > > > the gpio of cpu.
> > > This part confuses me, so does your chip have an actual regulator that
> > > needs to be enabled or is just a fake regulator whose gpio property is
> > > used not to enable the regulator but to toggle the WL_REG_ON pin of
> > > the WiFi chip?
> > another option would be to use the reset-gpio-handles. rk3288-veyron and I
> > think some Exynos as well use it that way.
> Yes I know, my point was that the reset-gpios property should be used
> instead of a fake regulator if what's needed is to toggle a chip pin.
>
> > > > Maybe, someone will say that can pull up/down from dts.
> > > > Unfortunately some SoCs can't support pinctrl pull up/down in
> > > > internal.
> > > Can you please elaborate on this? AFAIU this limitation is the reason
> > > why you went with the regulator approach so I think it deserve a more
> > > deep explanation.
> > On the rk3036 each pin has an individual unchangable pull direction. So it's
> > either no bias or pulling in the predefined direction (the pin_default bias
> > option).
> I think each change has to be justified on its own so I would say that
> having a regulator enabled as a part of a SDIO chip's power sequencing
> is something needed for many platforms, and that this provider should
> be extended to support that (something like commit msg in patch 05/12).
>
> And then in the kylin DTS change (patch 08/12), I would explain why a
> chained regulators approach is used/needed instead of the reset-gpios
> due any platform limitations.

Okay,
I 'm agreed with your points in here.

The reset-gpios/pwrsq can meet the demand of some wlan chips trigger 
condition.
No matter whatever is the BT_EN or WL_EN  triggers pin.

> > Heiko
> Best regards,


--
Thanks,
Caesar