linux-kernel - Re: [PATCH V5 3/7] arm64: dts: sc7280: Add QUPv3 wrapper

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Message-ID: <YRVKyJmJgwQObwFQ@google.com>
Date:   Thu, 12 Aug 2021 09:22:32 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajesh Patil <rajpat@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, swboyd@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, rnayak@...eaurora.org,
        saiprakash.ranjan@...eaurora.org, msavaliy@....qualcomm.com,
        skakit@...eaurora.org, Roja Rani Yarubandi <rojay@...eaurora.org>
Subject: Re: [PATCH V5 3/7] arm64: dts: sc7280: Add QUPv3 wrapper_0 nodes

On Thu, Aug 12, 2021 at 07:14:07AM -0700, Matthias Kaehlcke wrote:
> On Thu, Aug 12, 2021 at 01:11:14PM +0530, Rajesh Patil wrote:

> >  			qup_uart5_default: qup-uart5-default {
> >  				pins = "gpio46", "gpio47";
> >  				function = "qup13";
> >  			};
> 
> Wait, why does uart5 use the pins of qup13? Is see this is
> 'fixed' by '[4/7] arm64: dts: sc7280: Update QUPv3 UART5 DT
> node' but I'm still surprised ...
> 
> Doesn't 'fixing' this break devices that are currently using
> 'uart5'? It seems those devices would need to change from
> 'uart5' to 'uart11'.

Apparently the above configuration is bogus. I checked the schematic
of the IDP which uses uart5, the debug UART is on pins 22 and 23, aka
qup05. It seems uart5 works in spite of the bogus pinconf because the
default for the pins is their QUP function.