linux-kernel - [PATCH 2/2] arm64: dts: qcom: sc7280: Fix herobrine qspi pull direction

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Message-Id: <20230213165743.2.I06f9e461a85fcd5d6fb1e977aa253f6523096b6f@changeid>
Date:   Mon, 13 Feb 2023 16:57:52 -0800
From:   Douglas Anderson <dianders@...omium.org>
To:     Bjorn Andersson <andersson@...nel.org>
Cc:     amstan@...omium.org, swboyd@...omium.org, mka@...omium.org,
        Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] arm64: dts: qcom: sc7280: Fix herobrine qspi pull direction

Though it shouldn't matter very much, we've decided that it's slightly
better to park the qspi lines for herobrine with an internal pulldown
instead of an internal pullup. There is an external pulldown on one of
the data lines on the board and we don't want to have fighting pulls.
This also means that if the pulls somehow get left powered in S3
(which I'm uncertain about) that they won't be pulling up lines on an
unpowered SPI part.

Originally the pullup was picked because SPI transfers are active low
and thus the high state is somewhat more "idle", but that really isn't
that important because the chip select won't be asserted when the bus
is idle. The chip select has a nice external pullup on it that's
powered by the same power rail as the SPI flash.

This shouldn't have any functionality impact w/ reading/writing the
SPI since the lines are always push-pull when SPI transfers are
actually taking place.

Fixes: 116f7cc43d28 ("arm64: dts: qcom: sc7280: Add herobrine-r1")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi b/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
index b6137816f2f3..7d787b12c10f 100644
--- a/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
+++ b/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
@@ -703,7 +703,7 @@ &qspi_clk {

 &qspi_data01 {
 	/* High-Z when no transfers; nice to park the lines */
-	bias-pull-up;
+	bias-pull-down;
 	drive-strength = <8>;
 };

-- 
2.39.1.581.gbfd45094c4-goog