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

Emil Renner Berthing
2021-10-12T15:05:03Z

On Tue, 12 Oct 2021 at 16:31, Philipp Zabel <p.zabel@pengutronix.de> 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@esmil.dk>
> > ---
> > 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