On Fri 15 Apr 11:59 PDT 2016, Stephen Boyd wrote:
[..]
> ----8<-----
> From: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> Subject: [PATCH] Input: pmic8xxx-pwrkey: Fix algorithm for converting trigger
> delay
>
> The trigger delay algorithm that converts from microseconds to
> the register value looks incorrect. According to most of the PMIC
> documentation, the equation is
>
> delay (Seconds) = (1 / 1024) * 2 ^ (x + 4)
>
> except for one case where the documentation looks to have a
> formatting issue and the equation looks like
>
> delay (Seconds) = (1 / 1024) * 2 x + 4
>
> Most likely this driver was written with the improper
> documentation to begin with. According to the downstream sources
> the valid delays are from 2 seconds to 1/64 second, and the
> latter equation just doesn't make sense for that. Let's fix the
> algorithm and the range check to match the documentation and the
> downstream sources.
>
> Reported-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Acked-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> Cc: John Stultz <john.stultz@xxxxxxxxxx>
> Fixes: 92d57a73e410 ("input: Add support for Qualcomm PMIC8XXX power key")
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> ---
> drivers/input/misc/pmic8xxx-pwrkey.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/input/misc/pmic8xxx-pwrkey.c b/drivers/input/misc/pmic8xxx-pwrkey.c
> index 3f02e0e03d12..67aab86048ad 100644
> --- a/drivers/input/misc/pmic8xxx-pwrkey.c
> +++ b/drivers/input/misc/pmic8xxx-pwrkey.c
> @@ -353,7 +353,8 @@ static int pmic8xxx_pwrkey_probe(struct platform_device *pdev)
> if (of_property_read_u32(pdev->dev.of_node, "debounce", &kpd_delay))
> kpd_delay = 15625;
>
> - if (kpd_delay > 62500 || kpd_delay == 0) {
> + /* Valid range of pwr key trigger delay is 1/64 sec to 2 seconds. */
> + if (kpd_delay > USEC_PER_SEC * 2 || kpd_delay < USEC_PER_SEC / 64) {
> dev_err(&pdev->dev, "invalid power key trigger delay\n");
> return -EINVAL;
> }
> @@ -385,8 +386,8 @@ static int pmic8xxx_pwrkey_probe(struct platform_device *pdev)
> pwr->name = "pmic8xxx_pwrkey";
> pwr->phys = "pmic8xxx_pwrkey/input0";
>
> - delay = (kpd_delay << 10) / USEC_PER_SEC;
> - delay = 1 + ilog2(delay);
> + delay = (kpd_delay << 6) / USEC_PER_SEC;
> + delay = ilog2(delay);
Regards,
Bjorn
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