Enabling USART6 as a serial Port

[monica_s]

Hello ST,
      We are trying to enable USART6 as a serial console, in the stm32mp257f-dk board, we have builded the SDK using Openstlinux "Distribution package", I had done the below changes in the stm32mp257f-dk.dts device tree present in the kernel-source and u-boot directory : 

aliases {
    serial1 = &usart6;
	};
    chosen {
		stdout-path = "serial1:115200n8";  
		#address-cells = <2>;
		#size-cells = <2>;
		ranges;
           };

&usart2 {
	pinctrl-names = "default", "idle", "sleep";
	pinctrl-0 = <&usart2_pins_a>;
	pinctrl-1 = <&usart2_idle_pins_a>;
	pinctrl-2 = <&usart2_sleep_pins_a>;
	/delete-property/dmas;
	/delete-property/dma-names;
	status = "okay";
};

&usart6 {
	pinctrl-names = "default", "idle", "sleep";
	pinctrl-0 = <&usart6_pins_a>;
	pinctrl-1 = <&usart6_idle_pins_a>;
	pinctrl-2 = <&usart6_sleep_pins_a>;
	uart-has-rtscts;
	status = "okay";
};

 And also modified the stm32mp257f-dk-u-boot.dtsi device tree and pin configurations as shown below : 

&usart6 {
	bootph-all;
};

&usart6_pins_a {
	bootph-all;
	pins1 {
		bootph-all;
	};
	pins2 {
		bootph-all;
	};
};

But getting the below error :

E/TC:0   stm32_serc_handle_ilac:133 SERC exceptions [63:32]: 0x10
E/TC:0   stm32_serc_handle_ilac:139 SERC exception ID: 36

root@stm32mp25-disco-e3-cc-91:~# stty -F /dev/ttySTM1
E/TC:0   stm32_serc_handle_ilac:133 SERC exceptions [63:32]: 0x10
E/TC:0   stm32_serc_handle_ilac:139 SERC exception ID: 36
[  426.789010] SError Interrupt on CPU0, code 0x00000000bf000002 -- SError
[  426.789029] CPU: 0 PID: 1625 Comm: stty Tainted: G           O       6.6.78 #1
[  426.789039] Hardware name: STMicroelectronics STM32MP257F-DK Discovery Board (DT)
[  426.789044] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  426.789053] pc : stm32_usart_rx_dma_start_or_resume+0x80/0x234
[  426.789072] lr : stm32_usart_startup+0x8c/0x130
[  426.789082] sp : ffff8000839db950
[  426.789085] x29: ffff8000839db950 x28: ffff00008c143e40 x27: 0000000000020800
[  426.789101] x26: ffff800081037828 x25: ffff800081037468 x24: 0000000000000000
[  426.789113] x23: 0000000000000000 x22: ffff000081b23800 x21: ffff8000819ed048
[  426.789126] x20: 0000000000000000 x19: ffff800081b08210 x18: ffffffffffffffff
[  426.789138] x17: 0000000000000000 x16: 0000000000000000 x15: ffff8000839db700
[  426.789149] x14: 0000000000000001 x13: 006c61697265732e x12: 0000000000000000
[  426.789161] x11: ffff0000890e2920 x10: ffffffffffffffc0 x9 : ffffffffffffffff
[  426.789174] x8 : 0000000000000228 x7 : 0000000000000000 x6 : 0000000000000000
[  426.789185] x5 : ffff000081bad748 x4 : ffff000081bad808 x3 : 0000000000000000
[  426.789197] x2 : ffff800081dd5000 x1 : 0000000000000000 x0 : ffff0000824f2080
[  426.789211] Kernel panic - not syncing: Asynchronous SError Interrupt
[  426.789216] CPU: 0 PID: 1625 Comm: stty Tainted: G           O       6.6.78 #1
[  426.789223] Hardware name: STMicroelectronics STM32MP257F-DK Discovery Board (DT)
[  426.789227] Call trace:
[  426.789231]  dump_backtrace+0x94/0x114
[  426.789245]  show_stack+0x18/0x24
[  426.789256]  dump_stack_lvl+0x48/0x60
[  426.789265]  dump_stack+0x18/0x24
[  426.789272]  panic+0x324/0x380
[  426.789282]  nmi_panic+0x8c/0x90
[  426.789290]  arm64_serror_panic+0x6c/0x78
[  426.789298]  do_serror+0x3c/0x70
[  426.789304]  el1h_64_error_handler+0x30/0x48
[  426.789314]  el1h_64_error+0x64/0x68
[  426.789321]  stm32_usart_rx_dma_start_or_resume+0x80/0x234
[  426.789331]  stm32_usart_startup+0x8c/0x130
[  426.789341]  uart_startup+0x13c/0x2fc
[  426.789351]  uart_port_activate+0x34/0x9c
[  426.789360]  tty_port_open+0x8c/0x13c
[  426.789371]  uart_open+0x1c/0x30
[  426.789380]  tty_open+0x138/0x6dc
[  426.789388]  chrdev_open+0xbc/0x208
[  426.789400]  do_dentry_open+0x1b0/0x524
[  426.789413]  vfs_open+0x2c/0x38
[  426.789420]  path_openat+0xb14/0xdf0
[  426.789430]  do_filp_open+0x9c/0x14c
[  426.789440]  do_sys_openat2+0xc4/0x104
[  426.789447]  __arm64_sys_openat+0x64/0xac
[  426.789455]  invoke_syscall+0x48/0x114
[  426.789466]  el0_svc_common.constprop.0+0x40/0xe0
[  426.789476]  do_el0_svc+0x1c/0x28
[  426.789486]  el0_svc+0x38/0xc8
[  426.789493]  el0t_64_sync_handler+0x120/0x12c
[  426.789501]  el0t_64_sync+0x190/0x194
[  426.789510] SMP: stopping secondary CPUs
[  426.789527] Kernel Offset: disabled
[  426.789529] CPU features: 0x0,00000000,00020000,0000421b
[  426.789536] Memory Limit: none
[  427.047254] ---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]---
E/TC:1   Panic 'Watchdog' at /usr/src/debug/optee-os-stm32mp/4.0.0-stm32mp-r2/core/drivers/stm32_iwdg.c:218 <stm32_iwdg_it_handler>

then the device gets rebooted.

Can you suggest a simple straight forward documentation for resolving the SREC error as I am new the technology :)

[Christophe Guibout]

Hello @monica_s,

Most of the time, a SERC is caused by an unclocked hardware IP : see this wiki page for more details.

The SERC ID 36 corresponds to USART6 (see "Table 994. SERF resources mapping" in the reference manual)

I would recommand to also configure usart6 in op-tee which is owner of clock and security:

- clock needs to be set

- rif configuration has to be set to allow A35 to access the IP : default configuration looks good.

Don't forget to configure tf-a console as well.

BR,

Christophe