On Thu, Jan 05, 2017 at 03:23:24PM -0800, Stephen Boyd wrote: > On 01/05, Mark Rutland wrote: > > On APQ8060, the kernel crashes in arch_hw_breakpoint_init, taking an > > undefined instruction trap within write_wb_reg. This is because Scorpion > > CPUs erroneously appear to set DBGPRSR.SPD when WFI is issued, even if > > the core is not powered down. When DBGPRSR.SPD is set, breakpoint and > > watchpoint registers are treated as undefined. > > > > It's possible to trigger similar crashes later on from userspace, by > > requesting the kernel to install a breakpoint or watchpoint, as we can > > go idle at any point between the reset of the debug registers and their > > later use. This has always been the case. > > > > Given that this has always been broken, no-one has complained until now, > > and there is no clear workaround, disable hardware breakpoints and > > watchpoints on Scorpion to avoid these issues. > > I believe the workaround is to read DBGPRSR after exit from WFI? That might be do-able via cpuidle, but it's probably better for somebody familiar with the SoC PM to write that patch. > I'm fine with the blacklisting approach though. > > Reviewed-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx> Thanks, Will -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html