On Fri, Sep 05, 2025 at 01:41:49PM +0300, Jani Nikula wrote:
> 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 <[email protected]>
> Cc: Matt Roper <[email protected]>
> Cc: <[email protected]> # v5.9+
> Signed-off-by: Jani Nikula <[email protected]>
Good catch.
Reviewed-by: Matt Roper <[email protected]>
> ---
> 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 7340d5a71673..6f56ce939f00 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_power.c
> @@ -1174,7 +1174,7 @@ static void icl_mbus_init(struct intel_display *display)
> if (DISPLAY_VER(display) == 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(display, MBUS_ABOX_CTL(i), mask, val);
> }
>
> @@ -1639,11 +1639,11 @@ static void tgl_bw_buddy_init(struct intel_display
> *display)
> if (table[config].page_mask == 0) {
> drm_dbg_kms(display->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(display, 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(display, BW_BUDDY_PAGE_MASK(i),
> table[config].page_mask);
>
> --
> 2.47.2
>
--
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation
