Re: [Intel-gfx] [PATCH v2] drm/i915/dsi: let HW maintain CLK_POST

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 14 Sep 2023, William Tseng <william.tseng@intel.com> wrote:
> This change is to adjust TCLK-POST timing so DSI signaling can
> meet CTS specification.
>
> For clock lane, the TCLK-POST timing may be changed from
> 133.44 ns to 178.72 ns, which is greater than (60 ns+52*UI)
> and is conformed to the CTS standard.
>
> The computed UI is around 1.47 ns.
>
> v2: remove the change of HS-TRAIL.
>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
> Cc: Suraj Kandpal <suraj.kandpal@intel.com>
> Cc: Lee Shawn C <shawn.c.lee@intel.com>
> Signed-off-by: William Tseng <william.tseng@intel.com>

Thanks, pushed to drm-intel-next.

BR,
Jani.

> ---
>  drivers/gpu/drm/i915/display/icl_dsi.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c b/drivers/gpu/drm/i915/display/icl_dsi.c
> index ad6488e9c2b2..c4585e445198 100644
> --- a/drivers/gpu/drm/i915/display/icl_dsi.c
> +++ b/drivers/gpu/drm/i915/display/icl_dsi.c
> @@ -1822,7 +1822,7 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
>  	u32 prepare_cnt, exit_zero_cnt, clk_zero_cnt, trail_cnt;
>  	u32 ths_prepare_ns, tclk_trail_ns;
>  	u32 hs_zero_cnt;
> -	u32 tclk_pre_cnt, tclk_post_cnt;
> +	u32 tclk_pre_cnt;
>  
>  	tlpx_ns = intel_dsi_tlpx_ns(intel_dsi);
>  
> @@ -1869,15 +1869,6 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
>  		tclk_pre_cnt = ICL_TCLK_PRE_CNT_MAX;
>  	}
>  
> -	/* tclk post count in escape clocks */
> -	tclk_post_cnt = DIV_ROUND_UP(mipi_config->tclk_post, tlpx_ns);
> -	if (tclk_post_cnt > ICL_TCLK_POST_CNT_MAX) {
> -		drm_dbg_kms(&dev_priv->drm,
> -			    "tclk_post_cnt out of range (%d)\n",
> -			    tclk_post_cnt);
> -		tclk_post_cnt = ICL_TCLK_POST_CNT_MAX;
> -	}
> -
>  	/* hs zero cnt in escape clocks */
>  	hs_zero_cnt = DIV_ROUND_UP(mipi_config->ths_prepare_hszero -
>  				   ths_prepare_ns, tlpx_ns);
> @@ -1903,8 +1894,6 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
>  			       CLK_ZERO(clk_zero_cnt) |
>  			       CLK_PRE_OVERRIDE |
>  			       CLK_PRE(tclk_pre_cnt) |
> -			       CLK_POST_OVERRIDE |
> -			       CLK_POST(tclk_post_cnt) |
>  			       CLK_TRAIL_OVERRIDE |
>  			       CLK_TRAIL(trail_cnt));

-- 
Jani Nikula, Intel