Hi, we are having a problem with atomic accesses in pstore on some ARM CPUs (specifically rk3288 and rk3399). With those chips, atomic accesses fail with both pgprot_noncached and pgprot_writecombine memory. Atomic accesses do work when selecting PAGE_KERNEL protection.
Debugging on rk3399 shows the following crash. [ 0.912669] Bad mode in Error handler detected, code 0xbf000002 -- SError [ 0.920140] CPU: 4 PID: 1 Comm: swapper/0 Not tainted 4.4.14 #389 [ 0.926838] Hardware name: Google Kevin (DT) [ 0.931533] task: ffffffc0edfe0000 ti: ffffffc0edf7c000 task.ti: ffffffc0edf 7c000 [ 0.939780] PC is at __ll_sc___cmpxchg_case_mb_4+0x2c/0x5c [ 0.945811] LR is at 0x1 The "solution" for this problem in various Chrome OS releases is to disable atomic accesses in pstore entirely, which seems to be a bit brute-force. Question is what a proper upstream-acceptable solution might be. Introduce another memory type to select PAGE_KERNEL ? Is there some means to determine if atomic operations are supported with a given protection mask, maybe ? Anything else ? Thanks, Guenter
