On Wed, Mar 21, 2018 at 02:02:10PM +1100, NeilBrown wrote:
> 
> Since commit 3af5a67c86a3 ("MIPS: Fix early CM probing") the MT7621
> has not been able to boot.
> 
> This patched caused mips_cm_probe() to be called before
> mt7621.c::proc_soc_init().
> 
> prom_soc_init() has a comment explaining that mips_cm_probe()
> "wipes out the bootloader config" and means that configuration
> registers are no longer available.  It has some code to re-enable
> this config.
> 
> Before this re-enable code is run, the sysc register cannot be
> read, so when SYSC_REG_CHIP_NAME0 is read, a garbage value
> is returned and panic() is called.
> 
> If we move the config-repair code to the top of prom_soc_init(),
> the registers can be read and boot can proceed.
> 
> Very occasionally, the first register read after the reconfiguration
> returns garbage.  So I added a call to __sync().
> 
> Fixes: 3af5a67c86a3 ("MIPS: Fix early CM probing")
> Signed-off-by: NeilBrown <neil@brown.name>

Looks good. I've cosmetically tweaked commit message (mainly reflow),
added stable tag for 4.5+, and applied for 4.16.

Thanks
James