-----Original Message----- From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Thorsten Blum Sent: Friday, August 2, 2024 9:03 AM To: jani.nikula@xxxxxxxxxxxxxxx; joonas.lahtinen@xxxxxxxxxxxxxxx; Vivi, Rodrigo <rodrigo.vivi@xxxxxxxxx>; tursulin@xxxxxxxxxxx; airlied@xxxxxxxxx; daniel@xxxxxxxx Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Thorsten Blum <thorsten.blum@xxxxxxxxxx> Subject: [PATCH v2] drm/i915: Explicitly cast divisor and use div_u64() > > As the comment explains, the if check ensures that the divisor oa_period > is a u32. Explicitly cast oa_period to u32 to remove the following > Coccinelle/coccicheck warning reported by do_div.cocci: > > WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead > > Use the preferred div_u64() function instead of the do_div() macro and > remove the now unnecessary local variable tmp. > > Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxxx> > --- > Changes in v2: > - Use div_u64() instead of do_div() after feedback from Ville Syrjälä > - Link to v1: https://lore.kernel.org/linux-kernel/20240710074650.419902-2-thorsten.blum@xxxxxxxxxx/ > --- > drivers/gpu/drm/i915/i915_perf.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c > index 0b1cd4c7a525..f65fbe13ab59 100644 > --- a/drivers/gpu/drm/i915/i915_perf.c > +++ b/drivers/gpu/drm/i915/i915_perf.c > @@ -4096,15 +4096,13 @@ static int read_properties_unlocked(struct i915_perf *perf, > oa_period = oa_exponent_to_ns(perf, value); > > /* This check is primarily to ensure that oa_period <= > - * UINT32_MAX (before passing to do_div which only > + * UINT32_MAX (before passing it to div_u64 which only > * accepts a u32 denominator), but we can also skip > * checking anything < 1Hz which implicitly can't be > * limited via an integer oa_max_sample_rate. > */ > if (oa_period <= NSEC_PER_SEC) { > - u64 tmp = NSEC_PER_SEC; > - do_div(tmp, oa_period); > - oa_freq_hz = tmp; > + oa_freq_hz = div_u64(NSEC_PER_SEC, (u32)oa_period); > } else > oa_freq_hz = 0; Non-blocking suggestion: this looks like it can be inlined. And if the inline route is taken, it might be best to invert the conditional check like such: oa_freq_hz = oa_period > NSEC_PER_SEC ? 0 : div_u64(NSEC_PER_SEC, (u32)oa_period); I think this is just a matter of preference, though. The explicit if-else block is definitely clearer. Reviewed-by: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx> -Jonathan Cavitt > > -- > 2.45.2 > >
