Re: [PATCH v1 09/16] reset: starfive-jh7100: Add StarFive JH7100 reset driver

[Emil Renner Berthing <kernel@xxxxxxxx>]

On Tue, 12 Oct 2021 at 16:31, Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> wrote:
>
> On Tue, 2021-10-12 at 15:40 +0200, Emil Renner Berthing wrote:
> > Add a driver for the StarFive JH7100 reset controller.
> >
> > Signed-off-by: Emil Renner Berthing <kernel@xxxxxxxx>
> > ---
> >  MAINTAINERS                           |   7 ++
> >  drivers/reset/Kconfig                 |   8 ++
> >  drivers/reset/Makefile                |   1 +
> >  drivers/reset/reset-starfive-jh7100.c | 164 ++++++++++++++++++++++++++
> >  4 files changed, 180 insertions(+)
> >  create mode 100644 drivers/reset/reset-starfive-jh7100.c
> >
> [...]
> > diff --git a/drivers/reset/reset-starfive-jh7100.c b/drivers/reset/reset-starfive-jh7100.c
> > new file mode 100644
> > index 000000000000..26bc5b59c1f3
> > --- /dev/null
> > +++ b/drivers/reset/reset-starfive-jh7100.c
> > @@ -0,0 +1,164 @@
> [...]
> > +static int jh7100_reset_update(struct reset_controller_dev *rcdev,
> > +                            unsigned long id, bool assert)
> > +{
> > +     struct jh7100_reset *data = jh7100_reset_from(rcdev);
> > +     unsigned long offset = id / 32;
> > +     void __iomem *reg_assert = data->base + JH7100_RESET_ASSERT0 + 4 * offset;
> > +     void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + 4 * offset;
> > +     u32 mask = BIT(id % 32);
> > +     u32 done = jh7100_reset_asserted[offset] & mask;
> > +     unsigned long flags;
> > +     u32 value;
> > +
> > +     if (!assert)
> > +             done ^= mask;
> > +
> > +     spin_lock_irqsave(&data->lock, flags);
> > +
> > +     value = readl(reg_assert);
> > +     if (assert)
> > +             value |= mask;
> > +     else
> > +             value &= ~mask;
> > +     writel(value, reg_assert);
> > +
> > +     do {
> > +             value = readl(reg_status) & mask;
> > +     } while (value != done);
>
> Looking at the barebox driver, this could loop indefinitely if the
> caller forgets to enable the corresponding peripheral clock. Maybe
> use readl_poll_timeout() as a safety net.

You're right. Asserting without the clock enabled is fine, but
deasserting will hang forever. At least for the temperature sensor
clock/resets I tried it with. I'll add the timeout, thanks!

/Emil