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drm/dp: Add drm_dp_max_dprx_data_rate()

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Copy intel_dp_max_data_rate() to DRM core. It will be needed by a
follow-up DP tunnel patch, checking the maximum rate the DPRX (sink)
supports. Accordingly use the drm_dp_max_dprx_data_rate() name for
clarity. This patchset will also switch calling the new DRM function
in i915 instead of intel_dp_max_data_rate().

While at it simplify the function documentation/comments, removing
parts described already by drm_dp_bw_channel_coding_efficiency().

v2: (Ville)
- Remove max_link_rate_kbps.
- Simplify the function documentation.
v3:
- Rebased on latest drm-tip.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240226185246.1276018-1-imre.deak@intel.com
This commit is contained in:
Imre Deak 2024-02-26 20:52:43 +02:00
parent 610d7bc2e2
commit 1e59ab501a
2 changed files with 31 additions and 0 deletions
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30
drivers/gpu/drm/display/drm_dp_helper.c
View File

@ -4059,3 +4059,33 @@ int drm_dp_bw_channel_coding_efficiency(bool is_uhbr)
return 800000;
}
EXPORT_SYMBOL(drm_dp_bw_channel_coding_efficiency);
/**
* drm_dp_max_dprx_data_rate - Get the max data bandwidth of a DPRX sink
* @max_link_rate: max DPRX link rate in 10kbps units
* @max_lanes: max DPRX lane count
*
* Given a link rate and lanes, get the data bandwidth.
*
* Data bandwidth is the actual payload rate, which depends on the data
* bandwidth efficiency and the link rate.
*
* Note that protocol layers above the DPRX link level considered here can
* further limit the maximum data rate. Such layers are the MST topology (with
* limits on the link between the source and first branch device as well as on
* the whole MST path until the DPRX link) and (Thunderbolt) DP tunnels -
* which in turn can encapsulate an MST link with its own limit - with each
* SST or MST encapsulated tunnel sharing the BW of a tunnel group.
*
* Returns the maximum data rate in kBps units.
*/
int drm_dp_max_dprx_data_rate(int max_link_rate, int max_lanes)
{
int ch_coding_efficiency =
drm_dp_bw_channel_coding_efficiency(drm_dp_is_uhbr_rate(max_link_rate));
return DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate * 10 * max_lanes,
ch_coding_efficiency),
1000000 * 8);
}
EXPORT_SYMBOL(drm_dp_max_dprx_data_rate);

1
include/drm/display/drm_dp_helper.h
View File

@ -812,5 +812,6 @@ int drm_dp_bw_overhead(int lane_count, int hactive,
int dsc_slice_count,
int bpp_x16, unsigned long flags);
int drm_dp_bw_channel_coding_efficiency(bool is_uhbr);
int drm_dp_max_dprx_data_rate(int max_link_rate, int max_lanes);
#endif /* _DRM_DP_HELPER_H_ */