Linux/AM3354: UART3 issue on RX line

Mahesh Prajapati

Part Number: AM3354

Tool/software: Linux

Hi,

We are not getting data on processor AM3354 (UART3_RXD line not working). UART3_TXD perfectly working fine. Following schematics and dts configuration our board.

We are using the UART2, UART3 and UART4 only UART3 is not working rest of working perfectly. is there require the any specific configuration for UART3 for RX line

DTS

	uart2_pins: pinmux_uart2_pins {								
		pinctrl-single,pins = <
			0x12c (PIN_INPUT_PULLUP | MUX_MODE1)	/* mii1_txclk.UART2_RXD */
			0x130 (PIN_OUTPUT_PULLDOWN | MUX_MODE1)	/* mii1_rxclk.UART2_TXD */
		>;
	};

	uart3_pins: pinmux_uart3_pins {								
		pinctrl-single,pins = <
	  	0xf8 (PIN_INPUT_PULLUP     | MUX_MODE3)
		0x138 (PIN_OUTPUT_PULLDOWN  | MUX_MODE1)   /* mii1_rxd2.UART3_TXD */
			
		>;
	};

	uart4_pins: pinmux_uart4_pins {								
		pinctrl-single,pins = <
			0xf0 (PIN_INPUT             | MUX_MODE2) 		/* mmc0_dat3.UART4_CTS */
			0xf4 (PIN_OUTPUT_PULLDOWN   | MUX_MODE2) 	  /* mmc0_dat2.UART4_RTS */
			0x11c (PIN_INPUT_PULLUP     | MUX_MODE3)	    /* mmc0_data2.UART4_RXD */
			0x120 (PIN_OUTPUT_PULLDOWN  | MUX_MODE3)	    /* mii1_txd2.UART4_TXD */
		>;
	};

Hardware Schematic

Regards,

Mahesh.

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

Please post Linux version you use and relevant device tree portion.

0 Biser Gatchev-XID over 6 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Have you checked that the RXD signal is actually reaching the processor pin? Have you seen this issue on multiple boards?

0 Mahesh Prajapati over 6 years ago in reply to Biser Gatchev-XID

Intellectual 300 points

Kernel version is 4.4.32

0 Mahesh Prajapati over 6 years ago in reply to Biser Gatchev-XID

Intellectual 300 points

Yes, we have probe this line on oscilloscope and there is correct signal during the transaction. Same issue on multiple boards.

Regards,
Mahesh

0 Pavel Botev over 6 years ago in reply to Mahesh Prajapati

TI__Guru**** 170625 points

Mahesh,

You need to check conf_mmc0_dat1/0x44E108F8 register value from user space. You can use devmem2 or omapconf tool. Please provide me the value you have there.

Also check below dts file how uart pins are handled, AM33XX_IOPAD is used.

linux-kernel/arch/arm/boot/dts/am335x-icev2.dts

uart3_pins_default: uart3_pins_default {
pinctrl-single,pins = <
AM33XX_IOPAD(0x934, PIN_INPUT_PULLUP | MUX_MODE1) /* (L17) gmii1_rxd3.uart3_rxd */
AM33XX_IOPAD(0x938, PIN_OUTPUT_PULLUP | MUX_MODE1) /* (L16) gmii1_rxd2.uart3_txd */
>;
};

mmc0_pins_default: mmc0_pins_default {
pinctrl-single,pins = <
AM33XX_IOPAD(0x8f8, PIN_INPUT_PULLUP | MUX_MODE0) /* (G15) mmc0_dat1.mmc0_dat1 */

Regards,
Pavel

0 Mahesh Prajapati over 6 years ago in reply to Pavel Botev

Intellectual 300 points

Hi Pavel,

Thank for your input

We already reads this register value at user space for pin mux setting. register value is 0x33. it properly configured the mode 3, pull-up enabled and received enable.

Also verified dts file there is no conflict same pas (g15) use for other setting.

Regards,
Mahesh.

0 Pavel Botev over 6 years ago in reply to Mahesh Prajapati

TI__Guru**** 170625 points

Mahesh,

Check if you have enabled USB1 input to UART3_RXD. Check what values you have in registers USB_CTRL0 (UART2) and USB_CTRL1 (UART3). See the below TRM sections for details:

9.2.4.4.1 USB Control and Status
16.1.4 USB GPIO Details

Regards,
Pavel

0 Mahesh Prajapati over 6 years ago in reply to Pavel Botev

Intellectual 300 points

Hi Pavel,

We are not using the USB1 and also disable in dts file. Please refer the following value of register usb_ctlr0 and usb_ctlr1.

usb_ctlr0 = 0x3C186004 (BIT12-gpiomode value is 0)

usb_ctlr1 = 0x3C186004 (BIT12-gpiomode value is 0)

Please let me know if you have any questions.

Regards,

Mahesh.

0 Yordan Kovachev over 6 years ago in reply to Mahesh Prajapati

TI__Guru**** 161600 points

Hi,

Sorry for the delay. Just wanted to let you know that Pavel is OoO until Monday, so his feedback will be delayed.

Best Regards,
Yordan

0 Pavel Botev over 6 years ago in reply to Mahesh Prajapati

TI__Guru**** 170625 points

Mahesh,

I made a search but I can not find anything specific for UART3_RXD.

What I can suggest you is to make register dump of UART2/3/4 registers and compare the settings. You might have some UART3 misconfiguration in its registers.

Also I have found an e2e thread that is similar to your issue, and the root cause was HW malfunction:

https://e2e.ti.com/support/processors/f/791/t/579503

Regards,
Pavel

0 Pavel Botev over 6 years ago in reply to Pavel Botev

TI__Guru**** 170625 points

If you have no more questions related to the subject, please close/verify/resolve this thread.

Regards,
Pavel

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Linux/AM3354: UART3 issue on RX line