linux-kernel - Re: [PATCH v2 1/2] pinctrl: qcom: Add egpio feature support

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Date:   Fri, 29 Oct 2021 14:05:13 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>, agross@...nel.org,
        bjorn.andersson@...aro.org, linus.walleij@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, psodagud@...eaurora.org,
        dianders@...omium.org
Subject: Re: [PATCH v2 1/2] pinctrl: qcom: Add egpio feature support

Quoting Rajendra Nayak (2021-10-29 03:19:04)
>
>
> On 10/29/2021 12:24 PM, Stephen Boyd wrote:
> > Quoting Rajendra Nayak (2021-10-26 05:07:35)
> >> From: Prasad Sodagudi <psodagud@...eaurora.org>
> >>
> >> egpio is a scheme which allows special power Island Domain IOs
> >> (LPASS,SSC) to be reused as regular chip GPIOs by muxing regular
> >> TLMM functions with Island Domain functions.
> >> With this scheme, an IO can be controlled both by the cpu running
> >> linux and the Island processor. This provides great flexibility to
> >> re-purpose the Island IOs for regular TLMM usecases.
> >>
> >> 2 new bits are added to ctl_reg, egpio_present is a read only bit
> >> which shows if egpio feature is available or not on a given gpio.
> >> egpio_enable is the read/write bit and only effective if egpio_present
> >> is 1. Once its set, the Island IO is controlled from Chip TLMM.
> >> egpio_enable when set to 0 means the GPIO is used as Island Domain IO.
> >>
> >> To support this we add a new function 'egpio' which can be used to
> >> set the egpio_enable to 0, for any other TLMM controlled functions
> >> we set the egpio_enable to 1.
> >>
> >> Signed-off-by: Prasad Sodagudi <psodagud@...eaurora.org>
> >> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> >> ---
> >
> > Does this supersede adding support for lpass pinctrl in this series[1]?
>
> No, the driver in [1] actually manages the LPASS TLMM instance, while this patch
> makes it possible for the 'same' pins to be managed by the SoC TLMM instance.
> On sc7280 SoC for instance GPIO144-158 maps to LPI-GPIO-0-14, and GPIO159-174
> maps to SSC-GPIO-0-15.

How do we make sure that the LPASS pins are actually muxed out of the
SoC and not blocked by eGPIO in this driver muxing out the pin as a
gpio? Do they avoid conflicting with each other somehow?