On Mon, 04 Jun 2018, Charles Keepax wrote:
> Some Arizona CODECs have a small timing window where they will
> NAK an I2C transaction if it happens before the boot done bit is
> set. This can cause the read of the register containing the boot
> done bit to fail until it is set. Since regmap_read_poll_timeout
> will abort polling if a read fails it can't be reliably used to
> poll the boot done bit over I2C.
>
> Do a partial revert of ef84f885e037 ("mfd: arizona: Refactor
> arizona_poll_reg"), removing the regmap_read_poll_timeout but
> leaving the refactoring to make the arizona_poll_reg take more
> sensible arguments.
>
> Fixes: ef84f885e037 ("mfd: arizona: Refactor arizona_poll_reg")
> Signed-off-by: Charles Keepax <ckee...@opensource.cirrus.com>
> ---
>
> Changes since v1:
> - Explicitly include ktime header
> - Use USEC_PER_MSEC instead of a constant
> - Refactor the loop to not use a while (true)
>
> Thanks,
> Charles
>
> drivers/mfd/arizona-core.c | 29 ++++++++++++++++++++---------
> 1 file changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/mfd/arizona-core.c b/drivers/mfd/arizona-core.c
> index 83f1c5a516d99..fe0c151d9d9d7 100644
> --- a/drivers/mfd/arizona-core.c
> +++ b/drivers/mfd/arizona-core.c
> @@ -24,6 +24,7 @@
> #include <linux/regulator/consumer.h>
> #include <linux/regulator/machine.h>
> #include <linux/slab.h>
> +#include <linux/ktime.h>
> #include <linux/platform_device.h>
>
> #include <linux/mfd/arizona/core.h>
> @@ -240,18 +241,28 @@ static int arizona_poll_reg(struct arizona *arizona,
> int timeout_ms, unsigned int reg,
> unsigned int mask, unsigned int target)
> {
> + ktime_t timeout = ktime_add_us(ktime_get(), timeout_ms * USEC_PER_MSEC);
> unsigned int val = 0;
> - int ret;
> + int ret = regmap_read(arizona->regmap, reg, &val);
I'm not a fan of this type of initialisation.
Also, what's the point of assigning 'ret' if you never check it?
> - ret = regmap_read_poll_timeout(arizona->regmap,
> - reg, val, ((val & mask) == target),
> - ARIZONA_REG_POLL_DELAY_US,
> - timeout_ms * 1000);
> - if (ret)
> - dev_err(arizona->dev, "Polling reg 0x%x timed out: %x\n",
> - reg, val);
> + while (ktime_compare(ktime_get(), timeout) <= 0) {
> + if ((val & mask) == target)
> + return 0;
>
> - return ret;
> + usleep_range(ARIZONA_REG_POLL_DELAY_US / 2,
> + ARIZONA_REG_POLL_DELAY_US);
> +
> + ret = regmap_read(arizona->regmap, reg, &val);
> + }
> +
> + if (ret) {
> + dev_err(arizona->dev, "Failed polling reg 0x%x: %d\n",
> + reg, ret);
> + return ret;
> + }
> +
> + dev_err(arizona->dev, "Polling reg 0x%x timed out: %x\n", reg, val);
> + return -ETIMEDOUT;
> }
>
> static int arizona_wait_for_boot(struct arizona *arizona)
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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