On Tue, 07 Aug 2018, Richard Fitzgerald wrote:
> While polling for BOOT_DONE the chip could NAK a read because it is
> still booting, which would terminate the regmap_read_poll_timeout()
> with an error.
>
> Instead implement a polling loop that ignores read errors so we
> always poll until the chip signals boot or the loop times out.
>
> Signed-off-by: Richard Fitzgerald <[email protected]>
> ---
> drivers/mfd/madera-core.c | 38 ++++++++++++++++++++++++--------------
> 1 file changed, 24 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/mfd/madera-core.c b/drivers/mfd/madera-core.c
> index 8cfea969b060..bc5545c53ee5 100644
> --- a/drivers/mfd/madera-core.c
> +++ b/drivers/mfd/madera-core.c
> @@ -132,33 +132,43 @@ const char *madera_name_from_type(enum madera_type type)
> }
> EXPORT_SYMBOL_GPL(madera_name_from_type);
>
> -#define MADERA_BOOT_POLL_MAX_INTERVAL_US 5000
> -#define MADERA_BOOT_POLL_TIMEOUT_US 25000
> +#define MADERA_BOOT_POLL_INTERVAL_USEC 5000
> +#define MADERA_BOOT_POLL_TIMEOUT_USEC 25000
>
> static int madera_wait_for_boot(struct madera *madera)
> {
> - unsigned int val;
> - int ret;
> + ktime_t timeout;
> + unsigned int val = 0;
> + int ret = 0;
>
> /*
> * We can't use an interrupt as we need to runtime resume to do so,
> * so we poll the status bit. This won't race with the interrupt
> * handler because it will be blocked on runtime resume.
> + * The chip could NAK a read request while it is booting so ignore
> + * errors from regmap_read.
> */
> - ret = regmap_read_poll_timeout(madera->regmap,
> - MADERA_IRQ1_RAW_STATUS_1,
> - val,
> - (val & MADERA_BOOT_DONE_STS1),
> - MADERA_BOOT_POLL_MAX_INTERVAL_US,
> - MADERA_BOOT_POLL_TIMEOUT_US);
> -
> - if (ret)
> - dev_err(madera->dev, "Polling BOOT_DONE_STS failed: %d\n", ret);
> + regmap_read(madera->regmap, MADERA_IRQ1_RAW_STATUS_1, &val);
> + if (val & MADERA_BOOT_DONE_STS1)
> + goto done;
Move the usleep_range() invokation to after the regmap_read(), then
you can remove these 3 lines and have the same semantics.
> + timeout = ktime_add_us(ktime_get(), MADERA_BOOT_POLL_TIMEOUT_USEC);
> + do {
> + usleep_range(MADERA_BOOT_POLL_INTERVAL_USEC / 2,
> + MADERA_BOOT_POLL_INTERVAL_USEC);
> + regmap_read(madera->regmap, MADERA_IRQ1_RAW_STATUS_1, &val);
> + if (val & MADERA_BOOT_DONE_STS1)
> + goto done;
> + } while (ktime_compare(ktime_get(), timeout) <= 0);
> +
> + dev_err(madera->dev, "Polling BOOT_DONE_STS timed out\n");
> + ret = -ETIMEDOUT;
>
> /*
> * BOOT_DONE defaults to unmasked on boot so we must ack it.
> - * Do this unconditionally to avoid interrupt storms.
> + * Do this even after a timeout to avoid interrupt storms.
> */
> +done:
> regmap_write(madera->regmap, MADERA_IRQ1_STATUS_1,
> MADERA_BOOT_DONE_EINT1);
>
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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