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I am using 5.8 upstream linux kernel and running it on virt machine of QEMU. The dts shows that this machine already has a flash memory :

flash@0 {
        bank-width = <0x4>;
        reg = <0x0 0x0 0x0 0x4000000 0x0 0x4000000 0x0 0x4000000>;
        compatible = "cfi-flash";
    };

So I created partitions on it and want to use that for mtdoops. After struggling for a day, so, far, I am able to get the flash detected as mtddevice and the partitions also look ok.

/ # dmesg | grep -i mtd
[    0.000000] Kernel command line: console=ttyAMA0,115200n8 root=/dev/nfs rw nfsroot=192.168.122.1:/root/.repos/rootfs/arm64,nolock,vers=4,tcp ip=192.168.122.122 pstore.backend=mtdoops mtdoops.mtddev=0 printk.always_kmsg_dump mtdparts=0.flash:512k(mtdoops),18m(other)
[    1.203164] mtd device must be supplied (device name is empty)
[    1.213436] Concatenating MTD devices:
[    1.215403] 2 cmdlinepart partitions found on MTD device 0.flash
[    1.215693] Creating 2 MTD partitions on "0.flash":
[    1.216056] 0x000000000000-0x000000080000 : "mtdoops"
[    1.223686] mtdoops: Attached to MTD device 0
[    1.223784] mtdoops: ready 0, 1

However, when I trigger kernel panic using echo c > /proc/sysrq-trigger, the pstore logs are not written giving the error :

/ # echo c > /proc/sysrq-trigger
[  207.196767] sysrq: Trigger a crash
[  207.197679] Kernel panic - not syncing: sysrq triggered crash
[  207.198163] CPU: 1 PID: 137 Comm: sh Not tainted 5.8.0-dirty #6
...
...
[  207.206263] mtdoops: Cannot write from panic without panic_write
[  207.207001] Rebooting in 2 seconds..

I checked the source code in drivers/mtd/chips/ and I can see that cfi_cmdset_0002.c defines the panic_write handler. Even though I have enabled them in my config, but it appears from the message that this is supported only for few chips. Can anyone please hint or guide, if whatever i am trying is really possible or do I need to emulate a different NAND chip?

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