[PATCH 5.15 40/41] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk()

From: Greg Kroah-Hartman
Date: Fri Jan 14 2022 - 03:22:17 EST


From: Nathan Chancellor <nathan@xxxxxxxxxx>

commit 2e70570656adfe1c5d9a29940faa348d5f132199 upstream.

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@xxxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Suggested-by: Dávid Bolvanský <david.bolvansky@xxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20211014211916.3550122-1-nathan@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3063,9 +3063,9 @@ static void snb_wm_latency_quirk(struct
* 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;