Port.C of boot serial console is IO inverted on CoreMP135.
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The boot serial console can be accessed from Grove Port.C on the CoreMP135, via USB serial.
U-Boot logs are output from Port.C pin 1 (non TX-RX swap signal), while the Linux console is output from Port.C pin 2 (with TX-RX swap signal).
I would like to see the U-Boot logs and Linux console aligned on the same IO.
- U-Boot logs
from Port.C non TX-RX swap signal
NOTICE: CPU: STM32MP135D Rev.Y NOTICE: Model: STMicroelectronics STM32MP135F-DK Discovery Board NOTICE: BL2: v2.6-stm32mp1-r1.0(release):2021.05-10169-gb885d5525a NOTICE: BL2: Built : 15:39:25, May 15 2024 NOTICE: BL2: Booting BL32 optee optee: OP-TEE: revision 3.16 (b885d552) U-Boot 2021.10-stm32mp-r1 (May 15 2024 - 15:39:22 +0800) CPU: STM32MP135D Rev.? Model: STMicroelectronics STM32MP135F-DK Discovery Board Board: stm32mp1 in trusted mode (st,stm32mp135f-dk) DRAM: 512 MiB optee optee: OP-TEE: revision 3.16 (b885d552) Clocks: - MPU : 650 MHz - AXI : 266.500 MHz - PER : 24 MHz - DDR : 533 MHz WDT: Started with servicing (32s timeout) NAND: 0 MiB MMC: STM32 SD/MMC: 0 Loading Environment from MMC... OK In: serial Out: serial Err: serial invalid MAC address 0 in OTP 00:00:00:00:00:00 Net: No ethernet found. Hit any key to stop autoboot: 0 Boot over mmc0! switch to partitions #0, OK mmc0 is current device Scanning mmc 0:5... Found /boot/extlinux/extlinux.conf Retrieving file: /boot/extlinux/extlinux.conf 160 bytes read in 20 ms (7.8 KiB/s) 1: stm32mp135f-coremp135-buildroot Retrieving file: /boot/zImage 7923832 bytes read in 579 ms (13.1 MiB/s) append: root=/dev/mmcblk0p5 rw panic=5 quiet rootwait Retrieving file: /boot/stm32mp135f-coremp135.dtb 68116 bytes read in 24 ms (2.7 MiB/s) Kernel image @ 0xc2000000 [ 0x000000 - 0x78e878 ] ## Flattened Device Tree blob at c4000000 Booting using the fdt blob at 0xc4000000 Loading Device Tree to cffec000, end cffffa13 ... OK gc2145@3c node not found - DT update aborted FDT: cryp@54002000 node disabled for STM32MP135D Rev.? Starting kernel ...- Linux logs
from Port.C with TX-RX swap signal
[ 0.004005] /cpus/cpu@0 missing clock-frequency property [ 0.435138] stm32-cpufreq stm32-cpufreq: OPP-v2 not supported Starting syslogd: OK Starting klogd: OK Starting modules: soundcore success, snd success, snd_timer success, snd_pcm success, snd_pcm_dmaengine success, snd_soc_core success, snd_soc_simple_card_utils success, snd_soc_audio_graph_card success, snd-soc-simple-card success, snd_soc_stm32_sai success, snd_soc_stm32_sai_sub success, cdc-acm success, libcomposite success, g_serial success, OK Running sysctl: OK Starting mdev... OK Seeding 256 bits and crediting Saving 256 bits of creditable seed for next boot Starting tee-supplicant: Using device /dev/teepriv0. OK Starting network: OK Starting dhcpcd... dhcpcd-9.4.1 starting DUID 00:01:00:01:2d:f9:ec:09:2a:88:82:9b:b0:f0 forked to background, child pid 177 [ 5.966541] m_can_platform 4400e000.can can0: bit-timing not yet defined [ 5.974064] m_can_platform 4400e000.can can0: failed to open can device [ 5.988759] m_can_platform 4400f000.can can1: bit-timing not yet defined [ 5.994164] m_can_platform 4400f000.can can1: failed to open can device Starting dropbear sshd: OK Stopping /etc/rc.localOK # # ####### ##### ####### # ##### # # ## ## # # # # # # # # # # # # # # # # # # # # # # # # # ###### ##### # # # # ### # # # # # ####### # # # # # # # # # # # # # # # # # # ##### ##### # # # ##### # # Welcome to CoreMP135, Powered by M5Stack. CoreMP135 login:Reference
- U-Boot logs
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The uart6 in linux-dts was able to switch IO with rx-tx-swap.
The uart6 in uboot-dts seems to be fixed, unable to switch IO with rx-tx-swap.
Is there a HW issue with the Stm32MP135?
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According to the data sheet, is the IO of UART6 fixed at startup?
Reference：
https://www.st.com/ja/microcontrollers-microprocessors/stm32mp135d.html -
@nnn Yes its set at startup by the device tree overlay file.
I finally managed to find the config in the linux DTS file last night.
In order to redefine it you need to create a new Device Tree config to redefine the pins and functions. -
This discussion will be continued below
https://github.com/m5stack/CoreMP135_buildroot-external-st/issues/2
