On Tue, Apr 15, 2025 at 01:25:07PM +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)
>
> Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
> ---
> drivers/gpu/drm/display/drm_dp_helper.c | 47
> ++++++++++++++++-----------------
> include/drm/display/drm_dp_helper.h | 3 +++
> 2 files changed, 26 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c
> b/drivers/gpu/drm/display/drm_dp_helper.c
> index
> 57828f2b7b5a0582ca4a6f2a9be2d5909fe8ad24..1a5ff9ba6505f312ee41eb3bcc8b53d318411c03
> 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -4393,25 +4393,30 @@ 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)
> +/**
> + * drm_dp_link_symbol_cycles - calculate the link symbol count
> + * @lane_coount: DP link lane count
> + * @pixels: horizontal active pixels
> + * @bpp_x16: bits per pixel in .4 binary fixed format
> + * @symbol_size: DP symbol size
> + * @is_mst: is mst or sst
> + * @slice_count: number of slices
> + *
> + * Calculate the link symbol cycles for both dsc and non dsc case and
> + * return the count.
> + */
> +int drm_dp_link_symbol_cycles(int lane_count, int pixels, int bpp_x16,
> + int symbol_size, bool is_mst, int slice_count)
> {
> - int cycles = DIV_ROUND_UP(pixels * bpp_x16, 16 * symbol_size *
> lane_count);
> + int pix = slice_count ? DIV_ROUND_UP(pixels, slice_count) : pixels;
> + int cycles = DIV_ROUND_UP(pix * bpp_x16, 16 * symbol_size * lane_count);
> int align = is_mst ? 4 / lane_count : 1;
> + int slice_data_cycles = ALIGN(cycles, align);
>
> - 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)
> -{
> - 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;
> -
> - return slice_count * (slice_data_cycles + slice_eoc_cycles);
> + return slice_count ? (slice_count * (slice_data_cycles + align)) :
> + slice_data_cycles;
I'd like to preserve in the code what the DSC EOC cycles are and the way
the data symbol cycles are calculated could be kept as-is. So could
you instead do the following, renaming drm_dp_link_symbol_cycles() to
drm_dp_link_data_symbol_cycles()?:
-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)
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
> @@ -4486,15 +4491,9 @@ 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,
> + bpp_x16, symbol_size,
> + is_mst, dsc_slice_count);
>
> 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..22ae37e7870f1008acfc980a9b46d8dea1fbbe10
> 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -972,4 +972,7 @@ 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 bpp_x16,
> + int symbol_size, bool is_mst, int slice_count);
> +
> #endif /* _DRM_DP_HELPER_H_ */
>
> --
> 2.25.1
>
