On Tue, Mar 20 2018, Matt Redfearn wrote: > Hi Neil, > > > On 20/03/18 08:22, NeilBrown wrote: >> >> Further testing showed that the original version of this >> patch wasn't 100% reliable. Very occasionally the read >> of SYSC_REG_CHIP_NAME0 returns garbage. Repeating the >> read seems to be reliable, but it hasn't happened enough >> for me to be completely confident. >> So this version repeats that first read. > > You almost certainly need a sync() to ensure that the write to gcr_reg0 > has completed before attempting to read sysc + SYSC_REG_CHIP_NAME0. That sound like exactly the right sort of thing to do, though I assume you mean __sync(). I tried to reproduce the problem so I could test the fix, and of course I failed. Over 700 reboot cycles and never read any garbage from SYSC_REG_CHIP_NAME0. So I cannot test that this works, but I have tested that it doesn't cause any obvious regression. I'll send the v3 patch separately. Thanks a lot, NeilBrown
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