linux-kernel - Re: [PATCH 1/2] arm64: dts: qcom: sc7280-herobrine: Drop outputs on fpmcu pins

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Message-ID: <YjOt/aVJTLh4wqGo@google.com>
Date:   Thu, 17 Mar 2022 14:54:05 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Alexandru M Stan <amstan@...omium.org>
Subject: Re: [PATCH 1/2] arm64: dts: qcom: sc7280-herobrine: Drop outputs on
 fpmcu pins

On Wed, Mar 16, 2022 at 06:06:39PM -0700, Stephen Boyd wrote:
> Having these pins with outputs is good on a fresh boot because it puts
> the boot and reset pins in a known "good" state. Unfortunately, that
> conflicts with the fingerprint firmware flashing code. The firmware
> flashing process binds and unbinds the cros-ec and spidev drivers and
> that reapplies the pin output values after the flashing code has
> overridden the gpio values. This causes a problem because we try to put
> the device into bootloader mode, bind the spidev driver and that
> inadvertently puts it right back into normal boot mode, breaking the
> flashing process.
> 
> Fix this by removing the outputs. We'll introduce a binding for
> fingerprint cros-ec specifically to set the gpios properly via gpio APIs
> during cros-ec driver probe instead.
> 
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Matthias Kaehlcke <mka@...omium.org>
> Cc: Alexandru M Stan <amstan@...omium.org>
> Fixes: 116f7cc43d28 ("arm64: dts: qcom: sc7280: Add herobrine-r1")
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>

Reviewed-by: Matthias Kaehlcke <mka@...omium.org>