Amazing! This work looks awesome Imre, sorry it took me a little bit to get
back to this :). For all of the DP MST helper patches:
Reviewed-by: Lyude Paul <ly...@redhat.com>
On Thu, 2023-08-24 at 11:05 +0300, Imre Deak wrote:
> For fractional bpp values passed to the function in a .4 fixed point
> format, the fractional part is currently ignored due to scaling bpp too
> early. Fix this by scaling the overhead factor instead and to avoid an
> overflow multiplying bpp with the overhead factor instead of the clock
> rate.
>
> While at it simplify the formula, and pass the expected fixed point bpp
> values in the kunit tests.
>
> Cc: Lyude Paul <ly...@redhat.com>
> Cc: dri-de...@lists.freedesktop.org
> Signed-off-by: Imre Deak <imre.d...@intel.com>
> ---
> drivers/gpu/drm/display/drm_dp_mst_topology.c | 7 ++-----
> drivers/gpu/drm/tests/drm_dp_mst_helper_test.c | 8 ++++----
> 2 files changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index ed96cfcfa3040..bd0f35a0ea5fb 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -4712,12 +4712,9 @@ int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
> * factor in the numerator rather than the denominator to avoid
> * integer overflow
> */
> + u32 bpp_m = (dsc ? 64 / 16 : 64) * 1006 * bpp;
>
> - if (dsc)
> - return DIV_ROUND_UP_ULL(mul_u32_u32(clock * (bpp / 16), 64 *
> 1006),
> - 8 * 54 * 1000 * 1000);
> -
> - return DIV_ROUND_UP_ULL(mul_u32_u32(clock * bpp, 64 * 1006),
> + return DIV_ROUND_UP_ULL(mul_u32_u32(clock, bpp_m),
> 8 * 54 * 1000 * 1000);
> }
> EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
> diff --git a/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
> b/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
> index 545beea33e8c7..ea2182815ebe8 100644
> --- a/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
> +++ b/drivers/gpu/drm/tests/drm_dp_mst_helper_test.c
> @@ -40,15 +40,15 @@ static const struct drm_dp_mst_calc_pbn_mode_test
> drm_dp_mst_calc_pbn_mode_cases
> },
> {
> .clock = 332880,
> - .bpp = 24,
> + .bpp = 24 << 4,
> .dsc = true,
> - .expected = 50
> + .expected = 1191
> },
> {
> .clock = 324540,
> - .bpp = 24,
> + .bpp = 24 << 4,
> .dsc = true,
> - .expected = 49
> + .expected = 1161
> },
> };
>
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
