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

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Date:	Sat, 09 Jan 2016 03:42:03 +0100
From:	Heiko Stuebner <heiko@...ech.de>
To:	Javier Martinez Canillas <javier@....samsung.com>
Cc:	Caesar Wang <wxt@...k-chips.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-rockchip@...ts.infradead.org, leecam@...gle.com,
	leozwang@...gle.com, keescook@...gle.com,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alexandre Courbot <acourbot@...dia.com>,
	NeilBrown <neil@...wn.name>
Subject: Re: [PATCH v2 06/12] mmc: pwrseq: add support for power-on sequencing through DT

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.


> > 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).


Heiko