linux-kernel - Re: [PATCH] arm64: dts: qcom: Disable PON on Trogdor

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Date:   Wed, 2 Jun 2021 09:59:00 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>
Subject: Re: [PATCH] arm64: dts: qcom: Disable PON on Trogdor

Hi,

On Tue, Jun 1, 2021 at 11:44 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> We don't use the PON module on Trogdor devices. Instead the reboot
> reason is sort of stored in the 'eventlog' and the bootloader figures
> out if the boot is abnormal and records that there. Disable the PON node
> and then drop the power key disabling because that's a child node that
> will no longer be enabled if the PON node is disabled.
>
> Cc: Douglas Anderson <dianders@...omium.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Right. So essentially you're saying that the bootloader on trogdor
(coreboot / depthcharge) doesn't do anything with this and thus it
doesn't make sense on this board. That sounds right to me. Basically
there's no way in userspace to tell the bootloader to reboot into
recovery mode or developer mode. Those things need to be initiated
manually by the user.

It's possible that Qualcomm internally has some out-of-tree patches
where they use the PON for ramdump mode. +Rajendra as an FYI in case
there's somehow he should give a heads up to about this.

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