[PATCH v2] ARM: shmobile: Add early debugging support using SCIF(A)

[Geert Uytterhoeven]

On Wed, Oct 22, 2014 at 10:59 PM, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> On Wednesday 22 October 2014 19:34:17 Geert Uytterhoeven wrote:
>> On Wed, Oct 22, 2014 at 6:08 PM, Wolfram Sang <wsa at the-dreams.de> wrote:
>> >> I'm wondering whether this can be fixed in the i2c driver? Does it really
>> >> have to enable and disable the clock?
>> >
>> > From a power-saving PoV, this makes sense. I assume serial output works
>> > again as soon as the regular scif driver takes over? Isn't that a
>>
>> Yes it continues fine afterwards.
>> With TMU0 in DT, it's enabled again even earlier, as they share the parent.
>
> Would it make sense to have a list of clocks to reference from setup code when
> DEBUG_LL is defined ? It's a bit hackish, but DEBUG_LL is hackish anyway.

With setup code you mean platform or MSTP setup code?
That would be an option. The clock to enable depends on the SoC and SCIF(A)
address, so it's gonna need a large table.

>> BTW, the code in sh_mobile_i2c_init() does this:
>>
>>         /* Get clock rate after clock is enabled */
>>         clk_prepare_enable(pd->clk);
>>         i2c_clk_khz = clk_get_rate(pd->clk) / 1000;
>>         clk_disable_unprepare(pd->clk);
>>
>> I assume the enable/disable is no longer needed with CCF?
>
> I assume so as well.

Is it still needed with non-CCF? This driver is shared with arch/sh/.

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