On Thu, 24 Apr 2025, Arun R Murthy <arun.r.mur...@intel.com> wrote:
> Unify the function to calculate the link symbol cycles for both dsc and
> non-dsc case and export the function so that it can be used in the
> respective platform display drivers for other calculations.
>
> v2: unify the fn for both dsc and non-dsc case (Imre)
> v3: rename drm_dp_link_symbol_cycles to drm_dp_link_data_symbol_cycles
> retain slice_eoc_cycles as is (Imre)
> v4: Expose only drm_dp_link_symbol_cycles() (Imre)
> v6: Add slice pixels which was removed unknowingly (Vinod)
>
> Reviewed-by: Imre Deak <imre.d...@intel.com>
> Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
> ---
> drivers/gpu/drm/display/drm_dp_helper.c | 52
> +++++++++++++++++++++------------
> include/drm/display/drm_dp_helper.h | 2 ++
> 2 files changed, 36 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c
> b/drivers/gpu/drm/display/drm_dp_helper.c
> index
> 57828f2b7b5a0582ca4a6f2a9be2d5909fe8ad24..56c7e3318f01079c3bde492a21c76ed37e9724ca
> 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -4393,8 +4393,9 @@ EXPORT_SYMBOL(drm_panel_dp_aux_backlight);
> #endif
>
> /* See DP Standard v2.1 2.6.4.4.1.1, 2.8.4.4, 2.8.7 */
> -static int drm_dp_link_symbol_cycles(int lane_count, int pixels, int bpp_x16,
> - int symbol_size, bool is_mst)
> +static int drm_dp_link_data_symbol_cycles(int lane_count, int pixels,
> + int bpp_x16, int symbol_size,
> + bool is_mst)
> {
> int cycles = DIV_ROUND_UP(pixels * bpp_x16, 16 * symbol_size *
> lane_count);
> int align = is_mst ? 4 / lane_count : 1;
> @@ -4402,22 +4403,42 @@ static int drm_dp_link_symbol_cycles(int lane_count,
> int pixels, int bpp_x16,
> return ALIGN(cycles, align);
> }
>
> -static int drm_dp_link_dsc_symbol_cycles(int lane_count, int pixels, int
> slice_count,
> - int bpp_x16, int symbol_size, bool
> is_mst)
> +/**
> + * drm_dp_link_symbol_cycles - calculate the link symbol count with/without
> dsc
> + * @lane_count: DP link lane count
> + * @pixels: number of pixels in a scanline
> + * @dsc_slice_count: number of slices for DSC or '0' for non-DSC
> + * @bpp_x16: bits per pixel in .4 binary fixed format
> + * @symbol_size: DP symbol size
> + * @is_mst: %true for MST and %false for SST
> + *
> + * Calculate the link symbol cycles for both DSC (@dsc_slice_count !=0) and
> + * non-DSC case (@dsc_slice_count == 0) and return the count.
> + */
> +int drm_dp_link_symbol_cycles(int lane_count, int pixels, int
> dsc_slice_count,
> + int bpp_x16, int symbol_size, bool is_mst)
> {
> + int slice_count = dsc_slice_count ? : 1;
> int slice_pixels = DIV_ROUND_UP(pixels, slice_count);
> - int slice_data_cycles = drm_dp_link_symbol_cycles(lane_count,
> slice_pixels,
> - bpp_x16, symbol_size,
> is_mst);
> - int slice_eoc_cycles = is_mst ? 4 / lane_count : 1;
> + int slice_data_cycles = drm_dp_link_data_symbol_cycles(lane_count,
> + slice_pixels,
> + bpp_x16,
> + symbol_size,
> + is_mst);
> + int slice_eoc_cycles = 0;
> +
> + if (dsc_slice_count)
> + slice_eoc_cycles = is_mst ? 4 / lane_count : 1;
>
> return slice_count * (slice_data_cycles + slice_eoc_cycles);
> }
> +EXPORT_SYMBOL(drm_dp_link_symbol_cycles);
>
> /**
> * drm_dp_bw_overhead - Calculate the BW overhead of a DP link stream
> * @lane_count: DP link lane count
> * @hactive: pixel count of the active period in one scanline of the stream
> - * @dsc_slice_count: DSC slice count if @flags/DRM_DP_LINK_BW_OVERHEAD_DSC
> is set
> + * @dsc_slice_count: number of slices for DSC or '0' for non-DSC
> * @bpp_x16: bits per pixel in .4 binary fixed point
> * @flags: DRM_DP_OVERHEAD_x flags
> *
> @@ -4431,7 +4452,7 @@ static int drm_dp_link_dsc_symbol_cycles(int
> lane_count, int pixels, int slice_c
> * as well as the stream's
> * - @hactive timing
> * - @bpp_x16 color depth
> - * - compression mode (@flags / %DRM_DP_OVERHEAD_DSC).
> + * - compression mode (@dsc_slice_count != 0)
> * Note that this overhead doesn't account for the 8b/10b, 128b/132b
> * channel coding efficiency, for that see
> * @drm_dp_link_bw_channel_coding_efficiency().
> @@ -4486,15 +4507,10 @@ int drm_dp_bw_overhead(int lane_count, int hactive,
> WARN_ON((flags & DRM_DP_BW_OVERHEAD_UHBR) &&
> (flags & DRM_DP_BW_OVERHEAD_FEC));
>
> - if (flags & DRM_DP_BW_OVERHEAD_DSC)
After this series, intel_dp_mst_bw_overhead() will still pass in
DRM_DP_BW_OVERHEAD_DSC in flags, but it's no longer used for anything.
Is there going to be a follow-up, or what's the idea here?
BR,
Jani.
> - symbol_cycles = drm_dp_link_dsc_symbol_cycles(lane_count,
> hactive,
> - dsc_slice_count,
> - bpp_x16,
> symbol_size,
> - is_mst);
> - else
> - symbol_cycles = drm_dp_link_symbol_cycles(lane_count, hactive,
> - bpp_x16, symbol_size,
> - is_mst);
> + symbol_cycles = drm_dp_link_symbol_cycles(lane_count, hactive,
> + dsc_slice_count,
> + bpp_x16, symbol_size,
> + is_mst);
>
> return DIV_ROUND_UP_ULL(mul_u32_u32(symbol_cycles * symbol_size *
> lane_count,
> overhead * 16),
> diff --git a/include/drm/display/drm_dp_helper.h
> b/include/drm/display/drm_dp_helper.h
> index
> d9614e2c89397536f44bb7258e894628ae1dccc9..7b19192c70313d66dce1b7ba40dd59c14f80a182
> 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -971,5 +971,7 @@ int drm_dp_bw_channel_coding_efficiency(bool is_uhbr);
> int drm_dp_max_dprx_data_rate(int max_link_rate, int max_lanes);
>
> ssize_t drm_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc, struct dp_sdp
> *sdp);
> +int drm_dp_link_symbol_cycles(int lane_count, int pixels, int
> dsc_slice_count,
> + int bpp_x16, int symbol_size, bool is_mst);
>
> #endif /* _DRM_DP_HELPER_H_ */
--
Jani Nikula, Intel
