[PATCH 6.1.y] drm/i915/power: fix size for for_each_set_bit() in abox iteration

Sasha Levin
2025-09-14T20:17:03Z

From: Jani Nikula <jani.nikula@intel.com>

[ Upstream commit cfa7b7659757f8d0fc4914429efa90d0d2577dd7 ]

for_each_set_bit() expects size to be in bits, not bytes. The abox mask
iteration uses bytes, but it works by coincidence, because the local
variable holding the mask is unsigned long, and the mask only ever has
bit 2 as the highest bit. Using a smaller type could lead to subtle and
very hard to track bugs.

Fixes: 62afef2811e4 ("drm/i915/rkl: RKL uses ABOX0 for pixel transfers")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: stable@vger.kernel.org # v5.9+
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20250905104149.1144751-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 7ea3baa6efe4bb93d11e1c0e6528b1468d7debf6)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
[ adapted struct intel_display *display parameters to struct drm_i915_private *dev_priv ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/i915/display/intel_display_power.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
index 1a63da28f3300..8b8ba7426404a 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -1122,7 +1122,7 @@ static void icl_mbus_init(struct drm_i915_private *dev_priv)
if (DISPLAY_VER(dev_priv) == 12)
abox_regs |= BIT(0);

- for_each_set_bit(i, &abox_regs, sizeof(abox_regs))
+ for_each_set_bit(i, &abox_regs, BITS_PER_TYPE(abox_regs))
intel_de_rmw(dev_priv, MBUS_ABOX_CTL(i), mask, val);
}

@@ -1587,11 +1587,11 @@ static void tgl_bw_buddy_init(struct drm_i915_private *dev_priv)
if (table[config].page_mask == 0) {
drm_dbg(&dev_priv->drm,
"Unknown memory configuration; disabling address buddy logic.\n");
- for_each_set_bit(i, &abox_mask, sizeof(abox_mask))
+ for_each_set_bit(i, &abox_mask, BITS_PER_TYPE(abox_mask))
intel_de_write(dev_priv, BW_BUDDY_CTL(i),
BW_BUDDY_DISABLE);
} else {
- for_each_set_bit(i, &abox_mask, sizeof(abox_mask)) {
+ for_each_set_bit(i, &abox_mask, BITS_PER_TYPE(abox_mask)) {
intel_de_write(dev_priv, BW_BUDDY_PAGE_MASK(i),
table[config].page_mask);

--
2.51.0