AM4376: UART receive issue

Swapna yendrapalli

Part Number: AM4376

I am using a custom board based on the TI EVM for AM4376 and our linux drivers are based of kernel 4.1.13-rt11-g2046db6.

uart2 on AM4376 processor is externally connected to other uart interface.

When we snif the uart bus directly using logic analyzer we are seeing valid bytes without NULL

but

Reading /dev/ttys2 we see an extra NULL byte inserted in the message and all other bytes are as expected.

Our device tree has following definitions and looks like we don't have EDMA enabled

uart2_mws_pins_default: uart2_mws_pins_default {
pinctrl-single,pins = <
0x1f8 ( PIN_INPUT_PULLUP | MUX_MODE2 ) /* (AD22) cam1_data4.uart2_rxd */
0x1fc ( PIN_OUTPUT | MUX_MODE2 ) /* (AE23) cam1_data5.uart2_txd */
0x200 ( PIN_INPUT | MUX_MODE2 ) /* (AD23) cam1_data6.uart2_ctsn */
0x204 ( PIN_OUTPUT | MUX_MODE2 ) /* (AE24) cam1_data7.uart2_rtsn */
>;
};

&uart2 {
pinctrl-names = "default";
pinctrl-0 = <&uart2_mws_pins_default>;
status = "okay";
};

Could you please let us know if extra NULL bytes in uart2 receive buffer is a known issue ? If so, please advise how to fix it?

Thanks,

Swapna

over 7 years ago

0 Steve Kipisz over 7 years ago

TI__Genius 15510 points

Which SDK are you using?

Steve K.

0 Swapna yendrapalli over 7 years ago in reply to Steve Kipisz

Intellectual 625 points

Hi Steve,

I am using TI-SDK-2.0.0.1-kernel-4.1.13 .

Thanks,
Swapna

0 Steve Kipisz over 7 years ago in reply to Swapna yendrapalli

TI__Genius 15510 points

Can you try with the latest SDK?

Steve K.

0 Swapna yendrapalli over 7 years ago in reply to Steve Kipisz

Intellectual 625 points

I can try but it would take lot of effort to switch to new SDK. This is the SDK used for production sw.

Please advise if there is a known issue with UART driver/AM4376 UART module?

Thanks,
Swapna

0 Steve Kipisz over 7 years ago in reply to Swapna yendrapalli

TI__Genius 15510 points

I have not heard of any driver issues. As for the processor, there is nothing in the silicon errata.

Steve K.

0 Steve Kipisz over 7 years ago in reply to Steve Kipisz

TI__Genius 15510 points

Are you using the RT version? I noticed your first post had rt in the kernel version. If so I'll ask the RT person if he's heard of any issues.

Also, the 4.1.13 kernel is in the 2.0.1.7 SDK and I could not find a 2.0.0.1 SDK. We have a 2.0.0.0 with kernel version 4.1.6.

Steve K.

0 Swapna yendrapalli over 7 years ago in reply to Steve Kipisz

Intellectual 625 points

Hi Steve - we are using the Real time Linux Kernel. Sorry, You are right the SDK# is 2.0.1.7 and kernel is 4.1.13. Thanks!!

0 Swapna yendrapalli over 7 years ago in reply to Swapna yendrapalli

Intellectual 625 points

Hi Steve,

I digged a bit more into the kernel ( 4.1.13 from 2.0.1.7 sdk) driver code.

Looks like the corruption is happening in the tty layer . Uart seems to receive the data correctly.

Data received from UART
8250_core.c
serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr,
spinlock_t *flip_lock)
63 6d70 3d31 a66 313d 3139 3134

tty_io.c file :
static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
00000000: 63 00 6d 70 3d 31 0a 66 31 3d 31 39 31 34 32 35
00000010: 2e 30 30 30 0a 66 32 3d 31 39 31 34

There is a extra null in second byte .

Any help?

Thanks,
Swapna

0 Swapna yendrapalli over 7 years ago in reply to Swapna yendrapalli

Intellectual 625 points

Added to above: We are seeing RX overrun errors on the hardware side.

Any suggestions?

0 Swapna yendrapalli over 7 years ago in reply to Swapna yendrapalli

Intellectual 625 points

Hi Steve - Wondering if you got a chance to talk to your colleague to check if it is RT kernel issue and if there is any workaround/known patch for this issue?

0 Steve Kipisz over 7 years ago in reply to Swapna yendrapalli

TI__Genius 15510 points

Hi Swapna,

The colleague said he has not seen this on the RT kernel.

Steve K.

0 Swapna yendrapalli over 7 years ago in reply to Steve Kipisz

Intellectual 625 points

Thanks. Can baud rate be increased from 9600bps to 115200bps directly or should be done in steps ?

Processors

Processors forum

AM4376: UART receive issue