linux-kernel - [PATCH 4.14 055/106] arm64: dts: marvell: armada-37xx: Set pcie_reset

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Date:   Mon,  6 Dec 2021 15:56:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Marek Behún <marek.behun@....cz>,
        Remi Pommarel <repk@...plefau.lt>,
        Tomasz Maciej Nowak <tmn505@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        Marek Behún <kabel@...nel.org>
Subject: [PATCH 4.14 055/106] arm64: dts: marvell: armada-37xx: Set pcie_reset_pin to gpio function

From: Marek Behún <marek.behun@....cz>

commit 715878016984b2617f6c1f177c50039e12e7bd5b upstream.

We found out that we are unable to control the PERST# signal via the
default pin dedicated to be PERST# pin (GPIO2[3] pin) on A3700 SOC when
this pin is in EP_PCIE1_Resetn mode. There is a register in the PCIe
register space called PERSTN_GPIO_EN (D0088004[3]), but changing the
value of this register does not change the pin output when measuring
with voltmeter.

We do not know if this is a bug in the SOC, or if it works only when
PCIe controller is in a certain state.

Commit f4c7d053d7f7 ("PCI: aardvark: Wait for endpoint to be ready
before training link") says that when this pin changes pinctrl mode
from EP_PCIE1_Resetn to GPIO, the PERST# signal is asserted for a brief
moment.

So currently the situation is that on A3700 boards the PERST# signal is
asserted in U-Boot (because the code in U-Boot issues reset via this pin
via GPIO mode), and then in Linux by the obscure and undocumented
mechanism described by the above mentioned commit.

We want to issue PERST# signal in a known way, therefore this patch
changes the pcie_reset_pin function from "pcie" to "gpio" and adds the
reset-gpios property to the PCIe node in device tree files of
EspressoBin and Armada 3720 Dev Board (Turris Mox device tree already
has this property and uDPU does not have a PCIe port).

Signed-off-by: Marek Behún <marek.behun@....cz>
Cc: Remi Pommarel <repk@...plefau.lt>
Tested-by: Tomasz Maciej Nowak <tmn505@...il.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
Signed-off-by: Marek Behún <kabel@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/boot/dts/marvell/armada-3720-db.dts          |    3 +++
 arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts |    3 +++
 arch/arm64/boot/dts/marvell/armada-37xx.dtsi            |    2 +-
 3 files changed, 7 insertions(+), 1 deletion(-)

--- a/arch/arm64/boot/dts/marvell/armada-3720-db.dts
+++ b/arch/arm64/boot/dts/marvell/armada-3720-db.dts
@@ -155,6 +155,9 @@

 /* CON15(V2.0)/CON17(V1.4) : PCIe / CON15(V2.0)/CON12(V1.4) :mini-PCIe */
 &pcie0 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pcie_reset_pins &pcie_clkreq_pins>;
+	reset-gpios = <&gpiosb 3 GPIO_ACTIVE_LOW>;
 	status = "okay";
 };

--- a/arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts
+++ b/arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts
@@ -82,6 +82,9 @@

 /* J9 */
 &pcie0 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pcie_reset_pins &pcie_clkreq_pins>;
+	reset-gpios = <&gpiosb 3 GPIO_ACTIVE_LOW>;
 	status = "okay";
 };

--- a/arch/arm64/boot/dts/marvell/armada-37xx.dtsi
+++ b/arch/arm64/boot/dts/marvell/armada-37xx.dtsi
@@ -241,7 +241,7 @@

 				pcie_reset_pins: pcie-reset-pins {
 					groups = "pcie1";
-					function = "pcie";
+					function = "gpio";
 				};

 				pcie_clkreq_pins: pcie-clkreq-pins {