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SubjectRe: [PATCH] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk()
On Thu, Oct 14, 2021 at 02:21:43PM -0700, Nick Desaulniers wrote:
> On Thu, Oct 14, 2021 at 2:19 PM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > A new warning in clang points out a place in this file where a bitwise
> > OR is being used with boolean types:
> >
> > drivers/gpu/drm/i915/intel_pm.c:3066:12: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
> > changed = ilk_increase_wm_latency(dev_priv, dev_priv->wm.pri_latency, 12) |
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > This construct is intentional, as it allows every one of the calls to
> > ilk_increase_wm_latency() to occur (instead of short circuiting with
> > logical OR) while still caring about the result of each call.
> >
> > To make this clearer to the compiler, use the '|=' operator to assign
> > the result of each ilk_increase_wm_latency() call to changed, which
> > keeps the meaning of the code the same but makes it obvious that every
> > one of these calls is expected to happen.

Sure, why not.

> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1473
> > Reported-by: Nick Desaulniers <ndesaulniers@google.com>
>
> Thanks for the patch!
> Suggested-by: Dávid Bolvanský <david.bolvansky@gmail.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>

Thanks for the patch+review. Applied to drm-intel-next.

> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > ---
> > drivers/gpu/drm/i915/intel_pm.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index f90fe39cf8ca..aaa3a0998e4c 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -3050,9 +3050,9 @@ static void snb_wm_latency_quirk(struct drm_i915_private *dev_priv)
> > * The BIOS provided WM memory latency values are often
> > * inadequate for high resolution displays. Adjust them.
> > */
> > - changed = ilk_increase_wm_latency(dev_priv, dev_priv->wm.pri_latency, 12) |
> > - ilk_increase_wm_latency(dev_priv, dev_priv->wm.spr_latency, 12) |
> > - ilk_increase_wm_latency(dev_priv, dev_priv->wm.cur_latency, 12);
> > + changed = ilk_increase_wm_latency(dev_priv, dev_priv->wm.pri_latency, 12);
> > + changed |= ilk_increase_wm_latency(dev_priv, dev_priv->wm.spr_latency, 12);
> > + changed |= ilk_increase_wm_latency(dev_priv, dev_priv->wm.cur_latency, 12);
> >
> > if (!changed)
> > return;
> >
> > base-commit: d73b17465d6da0a94bc0fcc86b150e1e923e8f71
> > --
> > 2.33.1.637.gf443b226ca
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers

--
Ville Syrjälä
Intel

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