SK-AM62: How does TCA6424 IO Expander works

Gibbs Shih

Intellectual 2360 points

Part Number: SK-AM62
Other Parts Discussed in Thread: TCA6424,

Tool/software:

Hi, Dear Expert

The goal of this thread is try to let "uart1" of M.2 slots real inter-connect to AM62x uart1 (A18/B19/E19/A20)

So we need try to study how does TCA6424 IO Expander work?

Expander code as below.

What's mean for this DTS? show as below

		gpios = <&exp1 11 GPIO_ACTIVE_HIGH>;
		enable-active-high;

Does it mean "UART1_FET_BUF_EN" P12 of TCA6424 set high level?

Need your explanations.

Many Thanks

Gibbs

3 months ago

0 Bin Liu 3 months ago

TI__Guru*** 139346 points

Hi Gibbs,

gpios = <&exp1 11 GPIO_ACTIVE_HIGH>;
enable-active-high;

I am not sure where this code comes from. I don't see this in the SDK kernel source code. But anyway, please see the kernel device tree binding documentation (<kernel>/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml) for the explanation of "enable-active-high":

  enable-active-high:
    description:
      Polarity of GPIO is Active high. If this property is missing,
      the default assumed is Active low.
    type: boolean

0 Gibbs Shih 3 months ago in reply to Bin Liu

TI__Intellectual 2360 points

Hi, Bin

This code code come from CC33xx driver patch for AM62EVB

https://www.ti.com/product/zh-tw/CC3300#software-development

I believe should be "exp1" TCAN6424, and I wants to know how does it (IO expender) work.

diff --git arch/arm64/boot/dts/ti/k3-am625-sk.dts arch/arm64/boot/dts/ti/k3-am625-sk.dts
index 83525949aafd..4f97fad818fc 100644
--- arch/arm64/boot/dts/ti/k3-am625-sk.dts
+++ arch/arm64/boot/dts/ti/k3-am625-sk.dts
@@ -13,6 +13,10 @@ / {
 	compatible = "ti,am625-sk", "ti,am625";
 	model = "Texas Instruments AM625 SK";
 
+	aliases {
+		serial3 = &main_uart1;
+	};
+
 	opp-table {
 		/* Add 1.4GHz OPP for am625-sk board. Requires VDD_CORE to be at 0.85V */
 		opp-1400000000 {
@@ -105,7 +109,8 @@ wlan_lten: regulator-6 {
 		regulator-min-microvolt = <3300000>;
 		regulator-max-microvolt = <3300000>;
 		vin-supply = <&vcc_3v3_sys>;
-		gpios = <&exp1 11 GPIO_ACTIVE_LOW>;
+		gpios = <&exp1 11 GPIO_ACTIVE_HIGH>;
+		enable-active-high;
 	};
 
 	wlan_en: regulator-7 {
@@ -130,6 +135,15 @@ vdd_core: regulator-8 {
 		regulator-always-on;
 		regulator-boot-on;
 	};
+
+	uart_buf_en: regulator-9 {
+		compatible = "regulator-fixed";
+		regulator-name = "uart_buf_en";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+		gpios = <&exp1 10 GPIO_ACTIVE_LOW>;
+		regulator-always-on;
+	};
 };
 
 &main_pmx0 {
@@ -201,6 +215,27 @@ main_wlirq_pins_default: main-wlirq-pins-default {
 			AM62X_IOPAD(0x128, PIN_INPUT, 7) /* (B23) MMC2_SDWP.GPIO0_72 */
 		>;
 	};
+
+	main_uart1_pins_default: main-uart1-pins-default {
+		pinctrl-single,pins = < 
+			AM62X_IOPAD(0x1ac, PIN_INPUT, 2) /* (E19) MCASP0_AFSR.UART1_RXD */
+			AM62X_IOPAD(0x198, PIN_OUTPUT, 2) /* (A19) MCASP0_AXR2.UART1_RTSn */
+			AM62X_IOPAD(0x194, PIN_INPUT, 2) /* (B19) MCASP0_AXR3.UART1_CTSn */
+			AM62X_IOPAD(0x1b0, PIN_OUTPUT, 2) /* (A20) MCASP0_ACLKR.UART1_TXD */
+		>;
+	};
+};
+
+&main_uart1 {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&main_uart1_pins_default>;
+
+	bluetooth {
+		compatible = "ti,cc33xx-bt";
+		cc33xx-supply = <&wlan_en>;
+		max-speed = <115200>;
+	};
 };
 
 &main_i2c1 {
@@ -254,12 +289,12 @@ &sdhci2 {
 	#address-cells = <1>;
 	#size-cells = <0>;
 	wlcore: wlcore@2 {
-		compatible = "ti,wl1837";
+		compatible = "ti,cc33xx";
 		reg = <2>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&main_wlirq_pins_default>;
 		interrupt-parent = <&main_gpio0>;
-		interrupts = <72 IRQ_TYPE_EDGE_RISING>;
+		interrupts = <72 IRQ_TYPE_EDGE_FALLING>;
 	};
 };

I think this is one of key to enable uart1 enable.

gpios = <&exp1 11 GPIO_ACTIVE_HIGH>;
enable-active-high;

Many Thanks

Gibbs

0 Bin Liu 3 months ago in reply to Gibbs Shih

TI__Guru*** 139346 points

Hi Gibbs,

I am routing your query to the CC33xx device team for comments.

0 Sabeeh Khan1 3 months ago in reply to Bin Liu

TI__Mastermind 22920 points

Hello Gibbs,

"gpios = <&exp1 11 GPIO_ACTIVE_HIGH>" points to WL_LT_EN. It enables the TXS104 on the SK-Am62B-P1 board. This level translator is needed so that the "SOC_WLAN_EN_1V8" pin can be sent to the M.2 connector. Without it, the M.2 connector will not have access to WLAN_ENABLE pin.

+1 Sabeeh Khan1 3 months ago in reply to Sabeeh Khan1

TI__Mastermind 22920 points

To enable UART, add this regulator, which configures the UART1_FET_BUF_EN to be forced low:

+
+	uart_buf_en: regulator-9 {
+		compatible = "regulator-fixed";
+		regulator-name = "uart_buf_en";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+		gpios = <&exp1 10 GPIO_ACTIVE_LOW>;
+		regulator-always-on;
+	};

This patch is included in SDK 1.0.0.3: https://www.ti.com/tool/download/CC33XX-LINUX-MPU

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SK-AM62: How does TCA6424 IO Expander works