Hi Biju, Daniel,
On Mon, Nov 29, 2021 at 11:06 AM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> > Subject: Re: [PATCH v3 3/4] clocksource/drivers/renesas-ostm: Add RZ/G2L
> > OSTM support
> >
> > On 12/11/2021 19:44, Biju Das wrote:
> > > RZ/G2L SoC has Generic Timer Module(a.k.a OSTM) which needs to
> > > deassert the reset line before accessing any registers.
> > >
> > > This patch adds an entry point for RZ/G2L so that we can deassert the
> > > reset line in probe callback.
> >
> > What is the connection between adding the reset line control and the
> > platform driver at the end of the driver ?
>
> The original driver has no arm architecture timer, so it needs to be
s/driver/SoC used with this driver/
> called very early in the boot and using of calls for handling the clocks.
Hence must be handled by TIMER_OF_DECLARE().
> Where as RZ/G2L has arm architecture timer and it needs to release the module
> Reset before accessing any registers. So it has to be built in and it needs cpg driver
> which happens at later stage compared to the original case, for de-asserting the reset.
>
> Geert, please correct me if I am wrong.
The reset driver is not available yet at TIMER_OF_DECLARE() time,
so of_reset_control_get_optional_exclusive() returns -EPROBE_DEFER
on RZ/G2L. Fortunately there is no need to have this timer available
early on RZ/G2L, as it uses the arm architecture timer as the main
clock source. Still, to be available at all, the platform driver
is needed to support re-probing after the reset driver has become
available.
> > > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > > Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > > ---
> > > v2->v3:
> > > * Added reset_control_put() on error path.
> > > * enabled suppress_bind_attrs in ostm_device_driver structure
> > > v1->v2:
> > > * Added reset handling inside ostm_init
> > > * Used same compatible for builtin driver aswell
> > > ---
> > > drivers/clocksource/renesas-ostm.c | 39
> > > +++++++++++++++++++++++++++++-
> > > 1 file changed, 38 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clocksource/renesas-ostm.c
> > > b/drivers/clocksource/renesas-ostm.c
> > > index 3d06ba66008c..21d1392637b8 100644
> > > --- a/drivers/clocksource/renesas-ostm.c
> > > +++ b/drivers/clocksource/renesas-ostm.c
> > > @@ -9,6 +9,8 @@
> > > #include <linux/clk.h>
> > > #include <linux/clockchips.h>
> > > #include <linux/interrupt.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/reset.h>
> > > #include <linux/sched_clock.h>
> > > #include <linux/slab.h>
> > >
> > > @@ -159,6 +161,7 @@ static int __init ostm_init_clkevt(struct timer_of
> > > *to)
> > >
> > > static int __init ostm_init(struct device_node *np) {
> > > + struct reset_control *rstc;
> > > struct timer_of *to;
> > > int ret;
> > >
> > > @@ -166,6 +169,14 @@ static int __init ostm_init(struct device_node *np)
> > > if (!to)
> > > return -ENOMEM;
> > >
> > > + rstc = of_reset_control_get_optional_exclusive(np, NULL);
> > > + if (IS_ERR(rstc)) {
> > > + ret = PTR_ERR(rstc);
> > > + goto err_free;
> > > + }
> > > +
> > > + reset_control_deassert(rstc);
> > > +
> > > to->flags = TIMER_OF_BASE | TIMER_OF_CLOCK;
> > > if (system_clock) {
> > > /*
> > > @@ -178,7 +189,7 @@ static int __init ostm_init(struct device_node
> > > *np)
> > >
> > > ret = timer_of_init(np, to);
> > > if (ret)
> > > - goto err_free;
> > > + goto err_reset;
> > >
> > > /*
> > > * First probed device will be used as system clocksource. Any @@
> > > -203,9 +214,35 @@ static int __init ostm_init(struct device_node *np)
> > >
> > > err_cleanup:
> > > timer_of_cleanup(to);
> > > +err_reset:
> > > + reset_control_assert(rstc);
> > > + reset_control_put(rstc);
> > > err_free:
> > > kfree(to);
> > > return ret;
> > > }
> > >
> > > TIMER_OF_DECLARE(ostm, "renesas,ostm", ostm_init);
> > > +
> > > +#ifdef CONFIG_ARCH_R9A07G044
> > > +static int __init ostm_probe(struct platform_device *pdev) {
> > > + struct device *dev = &pdev->dev;
> > > +
> > > + return ostm_init(dev->of_node);
> > > +}
> > > +
> > > +static const struct of_device_id ostm_of_table[] = {
> > > + { .compatible = "renesas,ostm", },
> > > + { /* sentinel */ }
> > > +};
> > > +
> > > +static struct platform_driver ostm_device_driver = {
> > > + .driver = {
> > > + .name = "renesas_ostm",
> > > + .of_match_table = of_match_ptr(ostm_of_table),
> > > + .suppress_bind_attrs = true,
> > > + },
> > > +};
> > > +builtin_platform_driver_probe(ostm_device_driver, ostm_probe); #endif
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
