[PATCH] arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node

[PATCH] arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node

[Stephen Boyd]

We should indicate that we're not using the HPD pin on this device, per
the binding document. Otherwise if code in the future wants to enable
HPD in the bridge when this property is absent we'll be wasting power
powering hpd when we don't use it on trogdor boards. We didn't notice
this before because the kernel driver blindly disables hpd, but that
won't be true for much longer.

Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Cc: Douglas Anderson <dianders@chromium.org>
Fixes: 7ec3e67307f8 ("arm64: dts: qcom: sc7180-trogdor: add initial trogdor and lazor dt")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
index 07c8b2c926c0..298af6d7fb4a 100644
--- a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
+++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
@@ -595,6 +595,8 @@ sn65dsi86_bridge: bridge@2d {
 		clocks = <&rpmhcc RPMH_LN_BB_CLK3>;
 		clock-names = "refclk";
 
+		no-hpd;
+
 		ports {
 			#address-cells = <1>;
 			#size-cells = <0>;
-- 
https://chromeos.dev

Re: [PATCH] arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node

[Laurent Pinchart]

Hi Stephen,

Thank you for the patch.

On Tue, Mar 23, 2021 at 07:55:34PM -0700, Stephen Boyd wrote:
> We should indicate that we're not using the HPD pin on this device, per
> the binding document. Otherwise if code in the future wants to enable
> HPD in the bridge when this property is absent we'll be wasting power
> powering hpd when we don't use it on trogdor boards. We didn't notice
> this before because the kernel driver blindly disables hpd, but that
> won't be true for much longer.
> 
> Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> Cc: Douglas Anderson <dianders@chromium.org>
> Fixes: 7ec3e67307f8 ("arm64: dts: qcom: sc7180-trogdor: add initial trogdor and lazor dt")
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> index 07c8b2c926c0..298af6d7fb4a 100644
> --- a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> @@ -595,6 +595,8 @@ sn65dsi86_bridge: bridge@2d {
>  		clocks = <&rpmhcc RPMH_LN_BB_CLK3>;
>  		clock-names = "refclk";
>  
> +		no-hpd;
> +
>  		ports {
>  			#address-cells = <1>;
>  			#size-cells = <0>;

-- 
Regards,

Laurent Pinchart

Re: [PATCH] arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node

[Doug Anderson]

Hi,

On Tue, Mar 23, 2021 at 7:55 PM Stephen Boyd <swboyd@chromium.org> wrote:
>
> We should indicate that we're not using the HPD pin on this device, per
> the binding document. Otherwise if code in the future wants to enable
> HPD in the bridge when this property is absent we'll be wasting power
> powering hpd when we don't use it on trogdor boards. We didn't notice
> this before because the kernel driver blindly disables hpd, but that
> won't be true for much longer.
>
> Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> Cc: Douglas Anderson <dianders@chromium.org>
> Fixes: 7ec3e67307f8 ("arm64: dts: qcom: sc7180-trogdor: add initial trogdor and lazor dt")
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> index 07c8b2c926c0..298af6d7fb4a 100644
> --- a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> @@ -595,6 +595,8 @@ sn65dsi86_bridge: bridge@2d {
>                 clocks = <&rpmhcc RPMH_LN_BB_CLK3>;
>                 clock-names = "refclk";
>
> +               no-hpd;
> +

Sigh. I can't believe that I added this for cheza in commit
0d1ce0d14bd7 ("arm64: dts: sdm845: Add "no-hpd" to sn65dsi86 on
cheza") but forgot trogdor. Thanks.

Reviewed-by: Douglas Anderson <dianders@chromium.org>

NOTE: if you were feeling charitable you might consider sending a
patch for "sdm850-lenovo-yoga-c630.dts" as well.  I don't personally
know if HPD is hooked up on that system, but presumably even if it is
it's just as useless as it is on other systems where the bridge is
used for eDP. If nothing else setting it preserves existing behavior.
Someone (I forget who) requested that I word the bindings specifically
to say that "no-hpd" was OK to specify in cases like that, since the
bindings say:

>      Set if the HPD line on the bridge isn't hooked up to anything or is
>      otherwise unusable.

-Doug

Re: [PATCH] arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node

[Stephen Boyd]

Quoting Doug Anderson (2021-03-24 08:32:00)
> NOTE: if you were feeling charitable you might consider sending a
> patch for "sdm850-lenovo-yoga-c630.dts" as well.  I don't personally
> know if HPD is hooked up on that system, but presumably even if it is
> it's just as useless as it is on other systems where the bridge is
> used for eDP. If nothing else setting it preserves existing behavior.

Ok I can cook up another patch for this one too.

Re: [PATCH] arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node

[patchwork-bot+linux-arm-msm]

Hello:

This patch was applied to qcom/linux.git (refs/heads/for-next):

On Tue, 23 Mar 2021 19:55:34 -0700 you wrote:
> We should indicate that we're not using the HPD pin on this device, per
> the binding document. Otherwise if code in the future wants to enable
> HPD in the bridge when this property is absent we'll be wasting power
> powering hpd when we don't use it on trogdor boards. We didn't notice
> this before because the kernel driver blindly disables hpd, but that
> won't be true for much longer.
> 
> [...]

Here is the summary with links:
  - arm64: dts: qcom: trogdor: Add no-hpd to DSI bridge node
    https://git.kernel.org/qcom/c/5f551b5ce555

You are awesome, thank you!
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