linux-kernel - [PATCH 5.4 007/109] ARM: dts: omap4-droid4: Fix spi configuration and increase rate

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Date:   Tue, 14 Jul 2020 20:43:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, maemo-leste@...ts.dyne.org,
        Merlijn Wajer <merlijn@...zup.org>,
        Pavel Machek <pavel@....cz>,
        Sebastian Reichel <sre@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 007/109] ARM: dts: omap4-droid4: Fix spi configuration and increase rate

From: Tony Lindgren <tony@...mide.com>

[ Upstream commit 0df12a01f4857495816b05f048c4c31439446e35 ]

We can currently sometimes get "RXS timed out" errors and "EOT timed out"
errors with spi transfers.

These errors can be made easy to reproduce by reading the cpcap iio
values in a loop while keeping the CPUs busy by also reading /dev/urandom.

The "RXS timed out" errors we can fix by adding spi-cpol and spi-cpha
in addition to the spi-cs-high property we already have.

The "EOT timed out" errors we can fix by increasing the spi clock rate
to 9.6 MHz. Looks similar MC13783 PMIC says it works at spi clock rates
up to 20 MHz, so let's assume we can pick any rate up to 20 MHz also
for cpcap.

Cc: maemo-leste@...ts.dyne.org
Cc: Merlijn Wajer <merlijn@...zup.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Sebastian Reichel <sre@...nel.org>
Signed-off-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm/boot/dts/motorola-cpcap-mapphone.dtsi | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/motorola-cpcap-mapphone.dtsi b/arch/arm/boot/dts/motorola-cpcap-mapphone.dtsi
index 82f7ae030600d..ab91c4ebb1463 100644
--- a/arch/arm/boot/dts/motorola-cpcap-mapphone.dtsi
+++ b/arch/arm/boot/dts/motorola-cpcap-mapphone.dtsi
@@ -13,8 +13,10 @@
 		#interrupt-cells = <2>;
 		#address-cells = <1>;
 		#size-cells = <0>;
-		spi-max-frequency = <3000000>;
+		spi-max-frequency = <9600000>;
 		spi-cs-high;
+		spi-cpol;
+		spi-cpha;
 
 		cpcap_adc: adc {
 			compatible = "motorola,mapphone-cpcap-adc";
-- 
2.25.1