Re: [PATCH 07/13] ARM: dts: r8a7792: initial SoC device tree

Geert Uytterhoeven
2016-06-13T07:12:58Z

Hi Sergei,

On Fri, Jun 10, 2016 at 10:50 PM, Sergei Shtylyov
<sergei.shtylyov@cogentembedded.com> wrote:
> On 06/10/2016 11:42 PM, Geert Uytterhoeven wrote:
>>> The only problem I'm seeing (again) is the RCAN clock failing to
>>> register:
>>>
>>> rcar_gen2_cpg_clocks_init: failed to register cpg_clocks rcan clock (-12)
>>>
>>> I was going to look at it yesterday but (wrongly) thought it somehow
>>> cured itself... I'll look at it now.
>>
>> The RCAN parent is the second clock in the CPG node's "clocks" property,
>> which you didn't provide.
>
> Actually, the things are more complex. The figure 7.1c suggests that the
> RCAN clock has different parent on R8A7792 than on the other SoCs -- namely
> PLL1/VCO 1/4. That may be, since there's just no USB_EXTAL signal on this
> SoC (it doesn't seem to support any USB IPs). Which means the
> 'clk-rcar-gen2' driver can't work with the RCAN clock in its current form.

Right, I had forgotten about that.
Fortunately the clk-rcar-gen2 driver has a sane failure mode for this case ;-)

it seems the RCAN clock can just be modeled as a fixed clock. However,
its divider value isn't clear to me, as 15.9 MHz cannot be generated from PLL1
using an integer divider. Morimoto-san, can you please ask for clarification?

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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