| Message ID | 20201120073842.3232458-1-swboyd@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iio: sx9310: Fix semtech,avg-pos-strength setting when > 16 | expand |
Hi, On Thu, Nov 19, 2020 at 11:38 PM Stephen Boyd <swboyd@chromium.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@chromium.org> > Cc: Lars-Peter Clausen <lars@metafoo.de> > Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net> > Cc: Douglas Anderson <dianders@chromium.org> > Cc: Gwendal Grignou <gwendal@chromium.org> > Cc: Evan Green <evgreen@chromium.org> > Signed-off-by: Stephen Boyd <swboyd@chromium.org> > --- > > This fixes commit 5b19ca2c78a0 ("iio: sx9310: Set various settings from > DT") in the togreg branch. > > 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..5d8387ed9301 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 > 16 ? 4 : 3); Checking the math for the documented possible values of pos. What we want: 0 => 0 16 => 1 64 => 2 128 => 3 256 => 4 512 => 5 1024 => 6 4294967295 => 7 So looks OK. Do we care about anything other than the documented numbers? If my understanding of ilog2 is correct, then you'll get the wrong answer for 17. I think you could fix it with: pos = min(max(ilog2(pos), 3), 11) - (pos >= 32 ? 4 : 3); -Doug
Quoting Doug Anderson (2020-11-20 10:16:28) > > Checking the math for the documented possible values of pos. What we want: > > 0 => 0 > 16 => 1 > 64 => 2 > 128 => 3 > 256 => 4 > 512 => 5 > 1024 => 6 > 4294967295 => 7 > > So looks OK. Do we care about anything other than the documented > numbers? If my understanding of ilog2 is correct, then you'll get the > wrong answer for 17. I think you could fix it with: > > pos = min(max(ilog2(pos), 3), 11) - (pos >= 32 ? 4 : 3); > I don't think we really care about the rounding but to be consistent with the first two it is better to do that. I'll send a fix.
diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c index a2f820997afc..5d8387ed9301 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 > 16 ? 4 : 3); reg_def->def &= ~SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK; reg_def->def |= FIELD_PREP(SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK, pos);
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@chromium.org> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net> Cc: Douglas Anderson <dianders@chromium.org> Cc: Gwendal Grignou <gwendal@chromium.org> Cc: Evan Green <evgreen@chromium.org> Signed-off-by: Stephen Boyd <swboyd@chromium.org> --- This fixes commit 5b19ca2c78a0 ("iio: sx9310: Set various settings from DT") in the togreg branch. drivers/iio/proximity/sx9310.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) base-commit: 5b19ca2c78a0838976064c0347e46a2c859b541d