[PATCH] ARM: hw_breakpoint: blacklist Scorpion CPUs

[Linus Walleij]

On Thu, Jan 5, 2017 at 6:32 PM, Mark Rutland <mark.rutland at arm.com> 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.
>
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Reported-by: Linus Walleij <linus.walleij at linaro.org>
> Cc: Russell King <linux at armlinux.org.uk>
> Cc: Stephen Boyd <sboyd at codeaurora.org>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: stable at vger.kernel.org

Dammit git send-email does not add people on Reported-by to the
CC list so I missed this.

It works like a charm however, thanks for looking into this:
Tested-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij