[PATCH] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk()

[PATCH] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk()

[Nathan Chancellor]

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.

Link: https://github.com/ClangBuiltLinux/linux/issues/1473
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
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

Re: [PATCH] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk()

[Nick Desaulniers]

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.
>
> 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>

> 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

Re: [PATCH] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk()

[Ville Syrjälä]

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