Hi Simon,
On Mon, Mar 4, 2019 at 10:45 AM Simon Horman <horms@xxxxxxxxxxxx> wrote:
> On Fri, Mar 01, 2019 at 01:52:50PM +0100, Geert Uytterhoeven wrote:
> > On Thu, Feb 28, 2019 at 2:52 PM Simon Horman <horms+renesas@xxxxxxxxxxxx> wrote:
> > > Adds support for R-Car E3 (r8a77990) ZG clock.
> > >
> > > Signed-off-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> > > ---
> > > Tested on Ebisu to the extent that the clock rate is 600MHz on boot
> > > ---
> > > drivers/clk/renesas/r8a77990-cpg-mssr.c | 2 ++
> > > drivers/clk/renesas/rcar-gen3-cpg.c | 1 -
> > > drivers/clk/renesas/rcar-gen3-cpg.h | 1 +
> > > 3 files changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clk/renesas/r8a77990-cpg-mssr.c b/drivers/clk/renesas/r8a77990-cpg-mssr.c
> > > index 0e475dcb68b9..d0d29fc942ff 100644
> > > --- a/drivers/clk/renesas/r8a77990-cpg-mssr.c
> > > +++ b/drivers/clk/renesas/r8a77990-cpg-mssr.c
> > > @@ -83,6 +83,8 @@ static const struct cpg_core_clk r8a77990_core_clks[] __initconst = {
> > > DEF_FIXED("za8", R8A77990_CLK_ZA8, CLK_PLL0D8, 1, 1),
> > > DEF_GEN3_Z("z2", R8A77990_CLK_Z2, CLK_TYPE_GEN3_Z, CLK_PLL0,
> > > 4, CPG_FRQCRC, 8),
> > > + DEF_GEN3_Z("zg", R8A77990_CLK_ZG, CLK_TYPE_GEN3_Z, CLK_PLL0,
> > > + 8, CPG_FRQCRB, 24),
> >
> > While this approach may be correct for R-Car H3, M3-W, and M3-N, this is
> > not correct for R-Car E3, due to the presence of Spread Spectrum Clock
> > Generator support:
> > - When SCCG is enabled (MD12=1), the parent clock is either S0 or S1,
> > with only 2 or 3 (out of 32) supported dividers,
> > - When SCCG is disabled (MD12=0), the parent clock is PLL0, with only
> > 2 (out of 32) supported dividers.
> >
> > So I'm afraid the ZG clock on SCCG-capable SoCs needs its own very special
> > clock type.
>
> Thanks for pointing this out, I'll investigate further.
Given MD12 is sampled a reset time, there's no need to handle both cases
at runtime. I.e. if MD12=0, you can register a simple clock with one parent
and two dividers. If MD12=1, you can register a more complex custom clock
with two parents and 2 or 3 dividers.
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
