Update on my current research status.
1. To get normal read/write speed over USB3 I have to set max_sector_kb
to 64. Otherwise write is fine, but read is very slow (about 300kb/s).
Maybe this is hardware issue of this reader/card. However over USB2 all
works fine without any tweaks. All that said below is for case of
max_sector_kb = 64.
2. Stall and reset of device while mounting CF card from Thunar or
entering mount point with Midnight Commander was a consequence of
syscall statfs (I've ptraced mc). Google said this is a well known issue
of a vfat kernel module that was fixed some time ago, but a mount option
to workaround it still present and called "usefree". When this option is
supplied to mount command all works without any issues.
3. Also when I build kernel without CONFIG_PM option all works fine
without mount option "usefree".
Now I'm a bit confused by influence of CONFIG_PM and vfat mount option
on USB3 cardreader. Especially when reading and writing the whole CF in
reader using dd and corresponding /dev/sd? is done without any issues
and doesn't demand any tweaks like changing default value of max_sector_kb.
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