Hi Chris,
On Tue, Jan 24, 2017 at 3:20 PM, Chris Brandt <Chris.Brandt@xxxxxxxxxxx> wrote:
> On Tuesday, January 24, 2017, Geert Uytterhoeven wrote:
>> > Therefore, before I start firing off patches to remove runtime PM for
>> RZ/A, does anyone have an opinion one way of the other????
>>
>> Please have a look at Section 55.3.5 ("Module Standby Function"), which I
>> had never read myself, apparently...
>>
>> Seem like there is some kind of status register, the STBCR register
>> itself:
>>
>> Canceling Module Standby Function:
>> 1. Clear the MSTP bit to 0.
>> 2. After that, dummy-read the same register.
>>
>> Does it help if you add the dummy read when enabling the clock?
>
> Already tried that. And put a barrier() call just to make sure
> everything was done.
> It seems that might be enough for the RSPI, but the RIIC still has issues.
:-(
> From what I can tell, that makes the register space readable...but the IP block
> is not fully functional unless you delay a little.
If you know the minimum delay needed, and it's not too long, it can be
added to the enable path.
>> However, that section reveals another complicating factor for some
>> modules:
>> if the module has a bit in a STBREQn/STBACKn register, a module standy
>> request must be sent to the module before stopping the module clock.
>>
>> Looks like you're gonna need a whole new RZ/A1-specific clock driver to
>> handle all those details...
>
> There are only a couple IP blocks called out in the STBREQn/STBACKn registers,
> and I think they are not really crucial for runtime pm (Ethenret, LCD,
> Coresight, etc..).
> So in my opinion it's not worth a new driver just yet.
OK.
> But, I think I'd like to disable runtime pm for RZ/A1 in the drivers for now
> Because 'functional' is better than 'lower-power-but-broken'
I prefer not doing that in the individual drivers, as they're shared
with other SoCs.
I think you can handle that in drivers/clk/renesas/clk-mstp.c:
- in cpg_mstp_attach_dev(), add a call to pm_clk_resume(dev) after the
call to pm_clk_add_clk(),
- in cpg_mstp_detach_dev(), add a call to pm_clk_suspend(dev) before the
call to pm_clk_destroy().
Yes, that means the module clocks are enabled all the time.
Of course when running on RZ/A1H ;-)
Good luck!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
