[PATCH] ARM: dts: imx6q-cm-fx6: add sdio wifi/bt nodes

[christopher.spinrath at rwth-aachen.de]

From: Christopher Spinrath <christopher.spinrath at rwth-aachen.de>

The cm-fx6 module has an on-board AW-NH387 WiFi/BT module which is
based on Marvell's SD8787 chip and is connected to the usdhc1
controller.

Unfortunately, the chip gets unresponsive if the Bluetooth AMP
(Alternate Mac/Phy) function gets probed but the loaded firmware
doesn't support it. For instance, this is the case for the most
recent firmware in linux-firmware (Version 14.66.35.p52).

Thus, just add the required nodes but leave the usdhc1 node disabled
explicitly. Users who disabled the Bluetooth (AMP) support of their
OS can then conveniently enable WiFi (or even plain Bluetooth) support
with a simple device tree overlay/bootloader configuration.

Signed-off-by: Christopher Spinrath <christopher.spinrath at rwth-aachen.de>
---

Hi all,

some more information on the Bluetooth AMP dilemma: the vendor (CompuLab) just
remove Bluetooth AMP support from the kernel. However, this is not an option
here, since it would introduce a regression for its actual users.

Neither is degrading the firmware a good option: recent firmare (without AMP
support) provides WiFi that is more stable (in particular, for access points).

I wrote a RFC to linux-bluetooth [1] two weeks ago about this problem and the
only feedback I got was that Marvell has to provide information about how to
detect whether the firmware supports AMP properly -- but this is unlikely given
Marvell's information policy (in particular, since the sd8787 seems to be
unsupported as of now).

IMHO this patch is currently the best option, since it allows users in a
convenient way to enable WiFi support (e.g. no pinctrl handling in overlays),
even when they are using distribution kernels/device trees. Furthermore, the
hardware description is entirely accurate -- we have a driver/firmware problem
here.

Thanks,
Christopher

[1] https://www.spinics.net/lists/linux-bluetooth/msg70493.html

 arch/arm/boot/dts/imx6q-cm-fx6.dts | 41 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/arch/arm/boot/dts/imx6q-cm-fx6.dts b/arch/arm/boot/dts/imx6q-cm-fx6.dts
index a8af382..fe6ab0a 100644
--- a/arch/arm/boot/dts/imx6q-cm-fx6.dts
+++ b/arch/arm/boot/dts/imx6q-cm-fx6.dts
@@ -64,6 +64,14 @@
 		};
 	};
 
+	awnh387_pwrseq: pwrseq {
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_pwrseq>;
+		compatible = "mmc-pwrseq-sd8787";
+		powerdown-gpios = <&gpio7 12 GPIO_ACTIVE_HIGH>;
+		reset-gpios = <&gpio6 16 GPIO_ACTIVE_HIGH>;
+	};
+
 	reg_pcie_power_on_gpio: regulator-pcie-power-on-gpio {
 		compatible = "regulator-fixed";
 		regulator-name = "regulator-pcie-power-on-gpio";
@@ -304,6 +312,13 @@
 		>;
 	};
 
+	pinctrl_pwrseq: pwrseqgrp {
+		fsl,pins = <
+			MX6QDL_PAD_GPIO_17__GPIO7_IO12		0x1b0b0
+			MX6QDL_PAD_NANDF_CS3__GPIO6_IO16	0x1b0b0
+		>;
+	};
+
 	pinctrl_spdif: spdifgrp {
 		fsl,pins = <
 			MX6QDL_PAD_GPIO_16__SPDIF_IN  0x1b0b0
@@ -330,6 +345,17 @@
 			MX6QDL_PAD_EIM_D22__GPIO3_IO22	0x130b0
 		>;
 	};
+
+	pinctrl_usdhc1: usdhc1grp {
+		fsl,pins = <
+			MX6QDL_PAD_SD1_CMD__SD1_CMD	0x17071
+			MX6QDL_PAD_SD1_CLK__SD1_CLK	0x10071
+			MX6QDL_PAD_SD1_DAT0__SD1_DATA0	0x17071
+			MX6QDL_PAD_SD1_DAT1__SD1_DATA1	0x17071
+			MX6QDL_PAD_SD1_DAT2__SD1_DATA2	0x17071
+			MX6QDL_PAD_SD1_DAT3__SD1_DATA3	0x17071
+		>;
+	};
 };
 
 &pcie {
@@ -382,3 +408,18 @@
 	dr_mode = "otg";
 	status = "okay";
 };
+
+&usdhc1 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_usdhc1>;
+	mmc-pwrseq = <&awnh387_pwrseq>;
+	non-removable;
+	/*
+	 * If the OS probes the Bluetooth AMP function advertised on this bus
+	 * but the firmware in place does not support it, the WiFi/BT module
+	 * gets unresponsive.
+	 * Users who configured their OS properly can enable this node to gain
+	 * WiFi and/or plain Bluetooth support.
+	 */
+	status = "disabled";
+};
-- 
2.10.2