On Wed, Apr 23, 2025 at 06:23:33PM +0530, Arun R Murthy 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)
>
> Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
> ---
> drivers/gpu/drm/display/drm_dp_helper.c | 51
> +++++++++++++++++++++------------
> include/drm/display/drm_dp_helper.h | 2 ++
> 2 files changed, 35 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..d33a46016504ce52857b7c4e63d866af9c1eff34
> 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 +4403,41 @@ 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
Nit: missed in my previous review, but could be clearer by:
@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.
Nit: keep one space before '(' and after ')'.
> + */
> +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_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_count = dsc_slice_count ? : 1;
> + int slice_data_cycles = drm_dp_link_data_symbol_cycles(lane_count,
> + 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
Same nit as the above @dsc_slice_count one.
> * @bpp_x16: bits per pixel in .4 binary fixed point
> * @flags: DRM_DP_OVERHEAD_x flags
There is one more place referring to %DRM_DP_OVERHEAD_DSC in this
comment, could be changed to:
* - compression mode (@dsc_slice_count != 0)
Regardless of the nits, patch looks ok, thanks:
Reviewed-by: Imre Deak <imre.d...@intel.com>
After this patch DRM_DP_BW_OVERHEAD_DSC will be only set by the i915
driver, but it won't be used anywhere, so in a follow patch the flag
could be removed.
> *
> @@ -4486,15 +4506,10 @@ 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)
> - 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_ */
>
> --
> 2.25.1
>
