[PATCH/RFC] ARM: shmobile: sh7372: Keep D4 pm domain powered

[Geert Uytterhoeven]

Hi Simon,

On Mon, Oct 27, 2014 at 2:08 AM, Simon Horman <horms at verge.net.au> wrote:
> On Thu, Oct 23, 2014 at 01:31:14PM +0200, Geert Uytterhoeven wrote:
>> The D4 power domain contains the Coresight-ETM hardware block.
>> As long as the ARM debug/perf code doesn't use resource management with
>> runtime PM support, the D4 power domain must be kept powered to avoid a
>> crash during resume from s2ram (dbg_cpu_pm_notify() calls
>> reset_ctrl_regs() unconditionally, causing an undefined instruction
>> oops).
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
>> ---
>> Untested on real hardware, but a similar workaround is needed on r8a7740.
>
> I have hardware in the form of a Mackerel board and I'm happy
> to test this if it would help and you give me some guidance on how to do so.

That would be great!

Test procedure:
  1. echo 0 > /sys/module/printk/parameters/console_suspend
  2. echo mem > /sys/power/state
  3. [ Wake up by pressing a key on the serial console.
        There's no other wake-up source on mackerel? ]

Without my patch, I expect it to crash during resume in reset_ctrl_regs().

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds