linux-kernel - Re: [PATCH 05/13] arm64: dts: qcom: msm8916-samsung-serranove: Add sound and modem

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Date:   Tue, 26 Sep 2023 22:04:27 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: Re: [PATCH 05/13] arm64: dts: qcom: msm8916-samsung-serranove: Add
 sound and modem

On Tue, Sep 26, 2023 at 09:57:51PM +0200, Konrad Dybcio wrote:
> [...]
> 
> >>>  
> >>> +&sound {
> >>> +	status = "okay";
> >>> +	audio-routing =
> >>> +		"AMIC1", "MIC BIAS External1",
> >>> +		"AMIC2", "MIC BIAS Internal2",
> >>> +		"AMIC3", "MIC BIAS External1";
> >>> +};
> >> I *think* we should be able to harmlessly enable &audio globally?
> >>
> > 
> > What about boards that do not have/use audio at all? (see
> > msm8916-ufi.dtsi). We don't even want to load the kernel modules on
> > those.
> Is it really an issue other than losing a few kb of memory?
> 

Well, the msm8916-ufi.dtsi boards (basically USB modem/WiFi sticks)
have 512 MiB of RAM, with 85 MiB reserved for modem firmware, plus more
for TZ, HYP etc etc. That's not too much :D

> > 
> > IMO the SoC dtsi should always be minimal by default. This also
> > guarantees that you don't run into trouble because of half- or
> > incorrectly configured components during early bring-up, especially if
> > you don't have serial and are hoping to get the device booting far
> > enough to debug it.
> Generally I'd agree, but if the audio machine driver cannot NOP
> successfully without a topology configuration, that's a problem.
> 

I think it will effectively fail to probe because there are no DAI links
and no "model". I guess you could consider this to be a NOP but it's
confusing and takes away the attention from the actual errors in dmesg.

I would say it's disabled by default for the same reason that WiFi,
SDHCI, UFS etc etc are disabled by default. They simply don't do
anything useful without additional configuration & hardware support.

Thanks,
Stephan