linux-kernel - Re: [PATCH 1/3] drm/bridge: it6505: Modified power sequence

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Date:   Tue, 12 Jul 2022 17:08:03 +0800
From:   Pin-yen Lin <treapking@...omium.org>
To:     Robert Foss <robert.foss@...aro.org>
Cc:     allen <allen.chen@....com.tw>, Pin-yen Lin <treapking@...gle.com>,
        Jau-Chih Tseng <Jau-Chih.Tseng@....com.tw>,
        Kenneth Hung <Kenneth.Hung@....com.tw>,
        Hermes Wu <Hermes.Wu@....com.tw>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] drm/bridge: it6505: Modified power sequence

Hi Robert,

On Tue, Jul 12, 2022 at 4:07 PM Robert Foss <robert.foss@...aro.org> wrote:
>
> Hi Allen,
>
> On Thu, 7 Jul 2022 at 10:06, allen <allen.chen@....com.tw> wrote:
> >
> > From: allen chen <allen.chen@....com.tw>
> >
> > Change power sequence to meet it6505 data sheet requirement when boot on.
> >
> > Signed-off-by: Pin-Yen Lin <treapking@...omium.org>
> > Signed-off-by: Allen Chen <allen.chen@....com.tw>
> >
> > ---
> >  drivers/gpu/drm/bridge/ite-it6505.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> > index 2d119e3016b3..aa5e0aa1af85 100644
> > --- a/drivers/gpu/drm/bridge/ite-it6505.c
> > +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> > @@ -3029,7 +3029,7 @@ static int it6505_init_pdata(struct it6505 *it6505)
> >                 return PTR_ERR(pdata->ovdd);
> >         }
> >
> > -       pdata->gpiod_reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> > +       pdata->gpiod_reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
>
> Making this change is problematic since it requires a corresponding
> change in all of the device trees that use this device. It's against
> policy to change this interface after it has been introduced.
>
> Unless anyone thinks otherwise, I would like to see this patch dropped.

I don't really understand why this would require corresponding change
in device trees.

Currently there's no real it6505 user on upstream. Also, the GPIO
value will be changed
in it6505_poweron, so this change only affects the power on sequence of it6505.

>
> >         if (IS_ERR(pdata->gpiod_reset)) {
> >                 dev_err(dev, "gpiod_reset gpio not found");
> >                 return PTR_ERR(pdata->gpiod_reset);
> > --
> > 2.25.1
> >