netdev - Re: [linux-sunxi] Re: [PATCH 02/12] drm: sun4i: Add support for enabling DDC I2C bus to dw

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Message-ID: <20190408121727.4vdqdokr6w5thck6@core.my.home>
Date:   Mon, 8 Apr 2019 14:17:27 +0200
From:   Ondřej Jirman <megous@...ous.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Arend van Spriel <arend.vanspriel@...adcom.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-Hsien Lin <chi-hsien.lin@...ress.com>,
        Wright Feng <wright.feng@...ress.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Naveen Gupta <naveen.gupta@...ress.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-wireless <linux-wireless@...r.kernel.org>,
        brcm80211-dev-list.pdl@...adcom.com,
        brcm80211-dev-list@...ress.com,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [linux-sunxi] Re: [PATCH 02/12] drm: sun4i: Add support for
 enabling DDC I2C bus to dw_hdmi glue

On Mon, Apr 08, 2019 at 10:47:14AM +0200, Maxime Ripard wrote:
> On Mon, Apr 08, 2019 at 03:28:24PM +0800, Chen-Yu Tsai wrote:
> > On Mon, Apr 8, 2019 at 3:23 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> > >
> > > On Sat, Apr 06, 2019 at 01:45:04AM +0200, megous@...ous.com wrote:
> > > > From: Ondrej Jirman <megous@...ous.com>
> > > >
> > > > Orange Pi 3 board requires enabling DDC I2C bus via some GPIO connected
> > > > transistors, before it can be used. Model this as a power supply for DDC
> > > > (via regulator framework).
> > > >
> > > > Signed-off-by: Ondrej Jirman <megous@...ous.com>
> > >
> > > The DDC bus itself is usually attached to the HDMI connector, so it
> > > would make sense to make the supply also a property of the connector.
> >
> > I believe these are separate things. What this patch covers is power for
> > a voltage shifter between the SoC and HDMI DDC pins. The HDMI connector's
> > 5V supply to power the remote DDC chip is something else. And on the
> > Orange Pi 3 they are indeed separate supplies.
> 
> Then maybe the endpoint link between the two would be the best place
> to put this?

Interestingly &hdmi node configures the DDC bus pins via pinctrl on the SoC
side, so I put this there too, because it's related to those pins. I'm not sure
if that changes anything in the discussion.

regards,
   o.

> Maxime
> 
> --
> Maxime Ripard, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com