Hi Biju,
On Mon, Jun 14, 2021 at 2:26 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> On Fri, Jun 11, 2021 at 3:46 PM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> > Add clock entries for USB{0,1}.
> >
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> Thanks for your patch!
>
> > --- a/drivers/clk/renesas/r9a07g044-cpg.c
> > +++ b/drivers/clk/renesas/r9a07g044-cpg.c
> > @@ -88,6 +88,12 @@ static struct rzg2l_mod_clk r9a07g044_mod_clks[] = {
> > DEF_MOD("dmac", R9A07G044_CLK_DMAC,
> > R9A07G044_CLK_P1,
> > 0x52c, (BIT(0) | BIT(1)), (BIT(0) | BIT(1))),
> > + DEF_MOD("usb0", R9A07G044_CLK_USB0,
> > + R9A07G044_CLK_P1,
> > + 0x578, (BIT(0) | BIT(2) | BIT(3)), (BIT(0) | BIT(2) | BIT(3))),
> > + DEF_MOD("usb1", R9A07G044_CLK_USB1,
> > + R9A07G044_CLK_P1,
> > + 0x578, (BIT(1) | BIT(3)), (BIT(1) | BIT(3))),
> > DEF_MOD("scif0", R9A07G044_CLK_SCIF0,
> > R9A07G044_CLK_P0,
> > 0x584, BIT(0), BIT(0)),
>
> While the above matches the datasheet, I see a problem with the
> implementation. As BIT(3) of the CPG_{CLKON,CLKMON,RST}_USB is shared by
> the two USB2.0 channels, disabling USB_PCLK or asserting USB_PRESETN
> will affect both channels. So it looks like you need special handling
> to make sure that doesn't happen while the other channel is in use.
>
> Or am I missing something?
I'm getting the impression we do have to model the individual bits
as separate clocks (and resets). That would solve the problem with
the shared USB_PCLK, as the clock framework will take care of keeping
it enabled when at least one channel is in use.
Besides USB, SDHI has 4 clock bits, which we definitely don't want
to control together, as the card detect clock must not be stopped
while suspended.
However, the exception to the rule is Ethernet: each channel has
2 clocks, but only a single bit to control, so this needs a custom
single-gate-for-dual-clock driver.
Perhaps merging the clock binding definitions and initial driver for
v5.14 was a bit premature...
Anyway, we'll have 6 rcs after v5.14-rc1 to get it right ;-)
What do you think?
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
