linux-kernel - Re: [PATCH v2] iio: sx9310: Fix semtech,avg-pos-strength setting when

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Message-ID: <20201121145849.32e14ab9@archlinux>
Date:   Sat, 21 Nov 2020 14:58:49 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        Daniel Campello <campello@...omium.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Douglas Anderson <dianders@...omium.org>,
        Gwendal Grignou <gwendal@...omium.org>,
        Evan Green <evgreen@...omium.org>
Subject: Re: [PATCH v2] iio: sx9310: Fix semtech,avg-pos-strength setting
 when > 16

On Fri, 20 Nov 2020 10:29:44 -0800
Stephen Boyd <swboyd@...omium.org> wrote:

> This DT property can be 0, 16, and then 64, but not 32. The math here
> doesn't recognize this slight bump in the power of 2 numbers and
> translates a DT property of 64 into the register value '3' when it
> really should be '2'. Fix it by subtracting one more if the number being
> translated is larger than 16.
> 
> Cc: Daniel Campello <campello@...omium.org>
> Cc: Lars-Peter Clausen <lars@...afoo.de>
> Cc: Peter Meerwald-Stadler <pmeerw@...erw.net>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Gwendal Grignou <gwendal@...omium.org>
> Cc: Evan Green <evgreen@...omium.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
> 
> Changes from v1 (https://lore.kernel.org/r/20201120073842.3232458-1-swboyd@chromium.org):
>  * Changed ternary to consider 17 to 31 as the same as 16
> 
>  drivers/iio/proximity/sx9310.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c
> index a2f820997afc..ee1b4ff05a37 100644
> --- a/drivers/iio/proximity/sx9310.c
> +++ b/drivers/iio/proximity/sx9310.c
> @@ -1305,7 +1305,7 @@ sx9310_get_default_reg(struct sx9310_data *data, int i,
>  		if (ret)
>  			break;
>  
> -		pos = min(max(ilog2(pos), 3), 10) - 3;
> +		pos = min(max(ilog2(pos), 3), 11) - (pos >= 32 ? 4 : 3);

Given this is now rather tricky to read, I'd just do an explicit lookup of
the allowed values.  Probably just a switch statement.

Thanks,

Jonathan

>  		reg_def->def &= ~SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK;
>  		reg_def->def |= FIELD_PREP(SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK,
>  					   pos);
> 
> base-commit: 5b19ca2c78a0838976064c0347e46a2c859b541d