I notice that UART4 has been allocated to the BT/WIFI module. I have tried to switch the M7 console to UART1 on the primary header of the Dahlia board in FreeRTOS but subsequently booting Linux with UART1 disabled in device tree yields a kernel panic from the 8250 driver:
…
[ 0.743253] SoC: i.MX8MP revision 1.1
[ 0.746317] Bus freq driver module loaded
[ 0.755924] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[ 0.761546] 30880000.serial: ttymxc2 at MMIO 0x30880000 (irq = 34, base_baud = 1500000) is a IMX
[ 0.768275] printk: console [ttymxc2] enabled
[ 0.768275] printk: console [ttymxc2] enabled
[ 0.776908] printk: bootconsole [ec_imx6q0] disabled
[ 0.776908] printk: bootconsole [ec_imx6q0] disabled
[ 0.787316] 30890000.serial: ttymxc1 at MMIO 0x30890000 (irq = 35, base_baud = 1500000) is a IMX
[ 0.798886] Internal error: synchronous external abort: 96000210 [#1] PREEMPT SMP
[ 0.806382] Modules linked in:
[ 0.809445] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.77-6.1.0-devel+git.a8d2c55c6ae7 #1
[ 0.817982] Hardware name: Toradex Verdin iMX8M Plus WB on Dahlia Board (DT)
[ 0.825037] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=–)
[ 0.832012] pc : imx_uart_probe+0x31c/0x7d0
[ 0.836208] lr : imx_uart_probe+0x30c/0x7d0
[ 0.840401] sp : ffff800009c4bb60
[ 0.843717] x29: ffff800009c4bb60 x28: 0000000000000000 x27: ffff8000096b04c0
[ 0.850869] x26: ffff0000c0c74800 x25: 00000000fffffffa x24: 00000000fffffffa
[ 0.858019] x23: ffff0000c00fe810 x22: 000000000000002b x21: ffff0000c00fe800
[ 0.865166] x20: 0000000000000000 x19: ffff0000c0c35880 x18: ffffffffffffffff
[ 0.872316] x17: 647561625f657361 x16: 62202c3533203d20 x15: ffff0000c0c7438a
[ 0.879466] x14: ffffffffffffffff x13: 0000000000000018 x12: 0101010101010101
[ 0.886614] x11: 0000000000000000 x10: 0101010101010101 x9 : 0000000000000004
[ 0.893762] x8 : 0101010101010101 x7 : 7f7f7f7f7f7f7f7f x6 : fefefefefeff6f6c
[ 0.900912] x5 : 8080808080800000 x4 : 0000000000000010 x3 : 0000000000000000
[ 0.908061] x2 : 0000000000000000 x1 : ffff80000a3f0080 x0 : 0000000000000000
[ 0.915213] Call trace:
[ 0.917663] imx_uart_probe+0x31c/0x7d0
[ 0.921507] platform_probe+0x68/0xe0
[ 0.925181] really_probe+0xbc/0x46c
[ 0.928762] __driver_probe_device+0x114/0x190
[ 0.933212] driver_probe_device+0x40/0x100
[ 0.937404] __driver_attach+0xac/0x210
[ 0.941245] bus_for_each_dev+0x70/0xd0
[ 0.945088] driver_attach+0x24/0x30
[ 0.948674] bus_add_driver+0x144/0x244
[ 0.952516] driver_register+0x78/0x130
[ 0.956364] __platform_driver_register+0x28/0x34
[ 0.961076] imx_uart_init+0x3c/0x64
[ 0.964659] do_one_initcall+0x50/0x1b0
[ 0.968501] kernel_init_freeable+0x20c/0x290
[ 0.972866] kernel_init+0x24/0x12c
[ 0.976361] ret_from_fork+0x10/0x20
[ 0.979946] Code: 2a0003f4 35001820 f9400a61 91020021 (b9400021)
[ 0.986065] —[ end trace 0dde33e43dd32bd3 ]—
[ 0.990754] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[ 0.998418] SMP: stopping secondary CPUs
[ 1.002346] Kernel Offset: disabled
[ 1.005835] CPU features: 0x00002001,20000846
[ 1.010197] Memory Limit: none
[ 1.013255] —[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]—
Any help would be appreciated.
Thanks