how to use NAND Controller in linux kernel 5.4-stm32mp-r2?
I have modified STM32MP157C-DK2 board with NAND flash connected through FMC and it works properly with linux kernel 5.4-stm32mp-r1. I notice that there are some changes to FMC in 5.4-stm32mp-r2 and tried to build my custom linux using the newer release. Unfortunately, the kernel always crashed because it can't open the MTD device. The device can boot TF-A and u-boot properly but it always stuck at the kernel.
in 5.4-stm32mp-r1 version I only modify the DK2 device tree by stripping unused nodes, removing nodes that use the same pin as FMC, and adding FMC node by copying the configuration from stm32mp15xx-evx.dtsi. I use the same approach in 5.4-stm32mp-r2 as I assume the configuration from stm32mp15xx-evx.dtsi is enough to make the device boot from NAND.
[ 1.158408] UBI error: cannot open mtd UBI, error -2
[ 1.162737] stm32_rtc 5c004000.rtc: setting system clock to 2000-01-16T08:50:47 UTC (948012647)
[ 1.173134] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
[ 1.179147] Please append a correct "root=" boot option; here are the available partitions:
[ 1.187592] 0100 65536 ram0
[ 1.187596] (driver?)
[ 1.193642] 0101 65536 ram1
[ 1.193645] (driver?)
[ 1.199654] 0102 65536 ram2
[ 1.199657] (driver?)
[ 1.205750] 0103 65536 ram3
[ 1.205754] (driver?)
[ 1.211906] 0104 65536 ram4
[ 1.211910] (driver?)
[ 1.217898] 0105 65536 ram5
[ 1.217901] (driver?)
[ 1.223980] 0106 65536 ram6
[ 1.223983] (driver?)
[ 1.230269] 0107 65536 ram7
[ 1.230273] (driver?)
[ 1.236141] 0108 65536 ram8
[ 1.236144] (driver?)
[ 1.242243] 0109 65536 ram9
[ 1.242246] (driver?)
[ 1.248303] 010a 65536 ram10
[ 1.248306] (driver?)
[ 1.254473] 010b 65536 ram11
[ 1.254476] (driver?)
[ 1.260653] 010c 65536 ram12
[ 1.260656] (driver?)
[ 1.266808] 010d 65536 ram13
[ 1.266811] (driver?)
[ 1.272977] 010e 65536 ram14
[ 1.272980] (driver?)
[ 1.279144] 010f 65536 ram15
[ 1.279147] (driver?)
[ 1.285319] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[ 1.293566] CPU: 0 PID: 1 Comm: swapper Not tainted 5.4.56 #1
[ 1.299293] Hardware name: STM32 (Device Tree Support)
[ 1.304450] [<c010d5e0>] (unwind_backtrace) from [<c010b01c>] (show_stack+0x10/0x14)
[ 1.312163] [<c010b01c>] (show_stack) from [<c0116e08>] (panic+0x114/0x2fc)
[ 1.319118] [<c0116e08>] (panic) from [<c0901318>] (mount_block_root+0x248/0x2f8)
[ 1.326586] [<c0901318>] (mount_block_root) from [<c0901718>] (prepare_namespace+0x180/0x1c4)
[ 1.335097] [<c0901718>] (prepare_namespace) from [<c06157d8>] (kernel_init+0x8/0x110)
[ 1.343003] [<c06157d8>] (kernel_init) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
[ 1.350551] Exception stack(0xc7033fb0 to 0xc7033ff8)
[ 1.355594] 3fa0: 00000000 00000000 00000000 00000000
[ 1.363763] 3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 1.371927] 3fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 1.378534] ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]---I have another DK2 board without any modification and the kernel runs without any problem