From: Marek Behún marek.behun@nic.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@nic.cz Cc: Remi Pommarel repk@triplefau.lt Tested-by: Tomasz Maciej Nowak tmn505@gmail.com Acked-by: Thomas Petazzoni thomas.petazzoni@bootlin.com Signed-off-by: Gregory CLEMENT gregory.clement@bootlin.com Signed-off-by: Marek Behún kabel@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.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 @@ -128,6 +128,9 @@
/* 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 @@ -55,6 +55,9 @@
/* 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 @@ -256,7 +256,7 @@
pcie_reset_pins: pcie-reset-pins { groups = "pcie1"; - function = "pcie"; + function = "gpio"; };
pcie_clkreq_pins: pcie-clkreq-pins {