| Message ID | 20211115030320.26666-1-william.tseng@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/i915/dsi: let HW maintain the HS-TRAIL timing | expand |
diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c b/drivers/gpu/drm/i915/display/icl_dsi.c index 168c84a74d30..cd2f6ed51ed6 100644 --- a/drivers/gpu/drm/i915/display/icl_dsi.c +++ b/drivers/gpu/drm/i915/display/icl_dsi.c @@ -1948,17 +1948,13 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi) CLK_PRE_OVERRIDE | CLK_PRE(tclk_pre_cnt) | CLK_POST_OVERRIDE | - CLK_POST(tclk_post_cnt) | - CLK_TRAIL_OVERRIDE | - CLK_TRAIL(trail_cnt)); + CLK_POST(tclk_post_cnt)); /* data lanes dphy timings */ intel_dsi->dphy_data_lane_reg = (HS_PREPARE_OVERRIDE | HS_PREPARE(prepare_cnt) | HS_ZERO_OVERRIDE | HS_ZERO(hs_zero_cnt) | - HS_TRAIL_OVERRIDE | - HS_TRAIL(trail_cnt) | HS_EXIT_OVERRIDE | HS_EXIT(exit_zero_cnt));
This change is to avoid over-specification of the TEOT timing parameter, which is derived from software in current design. Supposed that THS-TRAIL and THS-EXIT have the minimum values, i.e., 60 and 100 in ns. If SW is overriding the HW default, the TEOT value becomes 150 ns, approximately calculated by the following formula. DIV_ROUND_UP(60/50)*50 + DIV_ROUND_UP(100/50))*50/2, where 50 is LP Escape Clock time in ns. The TEOT value 150 ns is larger than the maximum value, around 136 ns if UI is 1.8ns, (105 ns + 12*UI, defined by MIPI DPHY specification). However, the TEOT value will meet the specification if THS-TRAIL is set to the HW default, instead of software overriding. The timing change is made for both data lane and clock lane. Cc: Ville Syrjala <ville.syrjala@linux.intel.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Vandita Kulkarni <vandita.kulkarni@intel.com> Cc: Lee Shawn C <shawn.c.lee@intel.com> Cc: Cooper Chiou <cooper.chiou@intel.com> Signed-off-by: William Tseng <william.tseng@intel.com> --- drivers/gpu/drm/i915/display/icl_dsi.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)