linux-kernel - Re: [PATCH 1/5] dt-bindings: drm/bridge/synopsys: dw-hdmi: Add "unwedge" for ddc bus

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Message-ID: <20190605202101.GG17077@art_vandelay>
Date:   Wed, 5 Jun 2019 16:21:01 -0400
From:   Sean Paul <sean@...rly.run>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-rockchip@...ts.infradead.org,
        Neil Armstrong <narmstrong@...libre.com>,
        Mark Rutland <mark.rutland@....com>, mka@...omium.org,
        Sean Paul <seanpaul@...omium.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        David Airlie <airlied@...ux.ie>,
        linux-arm-kernel@...ts.infradead.org,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH 1/5] dt-bindings: drm/bridge/synopsys: dw-hdmi: Add
 "unwedge" for ddc bus

On Thu, May 02, 2019 at 03:53:32PM -0700, Douglas Anderson wrote:
> In certain situations it was seen that we could wedge up the DDC bus
> on the HDMI adapter on rk3288.  The only way to unwedge was to mux one
> of the pins over to GPIO output-driven-low temporarily and then
> quickly mux back.  Full details can be found in the patch
> ("drm/bridge/synopsys: dw-hdmi: Add "unwedge" for ddc bus").
> 
> Since unwedge requires remuxing the pins, we first need to add to the
> bindings so that we can specify what state the pins should be in for
> unwedging.

Pushed to drm-misc-next along with patch 2. I'll let Heiko land the dts patches.

Thanks!

Sean

> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>  .../bindings/display/rockchip/dw_hdmi-rockchip.txt         | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/rockchip/dw_hdmi-rockchip.txt b/Documentation/devicetree/bindings/display/rockchip/dw_hdmi-rockchip.txt
> index 39143424a474..8346bac81f1c 100644
> --- a/Documentation/devicetree/bindings/display/rockchip/dw_hdmi-rockchip.txt
> +++ b/Documentation/devicetree/bindings/display/rockchip/dw_hdmi-rockchip.txt
> @@ -38,6 +38,13 @@ Optional properties
>  - phys: from general PHY binding: the phandle for the PHY device.
>  - phy-names: Should be "hdmi" if phys references an external phy.
>  
> +Optional pinctrl entry:
> +- If you have both a "unwedge" and "default" pinctrl entry, dw_hdmi
> +  will switch to the unwedge pinctrl state for 10ms if it ever gets an
> +  i2c timeout.  It's intended that this unwedge pinctrl entry will
> +  cause the SDA line to be driven low to work around a hardware
> +  errata.
> +
>  Example:
>  
>  hdmi: hdmi@...80000 {
> -- 
> 2.21.0.1020.gf2820cf01a-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS