linux-kernel - Re: [PATCH] arm64: dts: mediatek: mt8192-asurada: Add off-on-delay-us for pp3300

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Tue, 30 Apr 2024 10:17:05 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Pin-yen Lin <treapking@...omium.org>,
 Matthias Brugger <matthias.bgg@...il.com>
Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
 <devicetree@...r.kernel.org>,
 "moderated list:ARM/Mediatek SoC support"
 <linux-arm-kernel@...ts.infradead.org>,
 "moderated list:ARM/Mediatek SoC support"
 <linux-mediatek@...ts.infradead.org>,
 Nícolas F . R . A . Prado <nfraprado@...labora.com>,
 "open list:ARM/Mediatek SoC support" <linux-kernel@...r.kernel.org>,
 Hsin-Te Yuan <yuanhsinte@...omium.org>
Subject: Re: [PATCH] arm64: dts: mediatek: mt8192-asurada: Add off-on-delay-us
 for pp3300_mipibrdg

Il 29/04/24 11:53, Pin-yen Lin ha scritto:
> Set off-on-delay-us to 500000 us for pp3300_mipibrdg to make sure it
> complies with the panel sequence. Explicit configuration on the
> regulator node is required because mt8192-asurada uses the same power
> supply for the panel and the anx7625 DP bridge. So powering on/off the
> DP bridge could break the power sequence requirement for the panel.
> 
> Fixes: f9f00b1f6b9b ("arm64: dts: mediatek: asurada: Add display regulators")
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> 

Uhm, there might be more to it - I don't think that this should ever happen.

The regulator is refcounted, so...
  * Bridge on: panel goes off, but regulator doesn't turn off (refcount=1)
    * Panel resume -> sequence respected (refcount=2 -> wait -> more vregs, etc)
  * Bridge off: panel is already off (refcount=0)
    * Bridge resume -> refcount=1, no panel commands yet
    * Panel resume -> refcount=2, wait -> more vregs, etc

Can you please describe the issue that you're getting?

Cheers,
Angelo

> ---
> 
>   arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
> index 7a704246678f..08d71ddf3668 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
> @@ -147,6 +147,7 @@ pp3300_mipibrdg: regulator-3v3-mipibrdg {
>   		regulator-boot-on;
>   		gpio = <&pio 127 GPIO_ACTIVE_HIGH>;
>   		vin-supply = <&pp3300_g>;
> +		off-on-delay-us = <500000>;
>   	};
>   
>   	/* separately switched 3.3V power rail */