Re: [GLK MIPI DSI V3 1/7] drm/i915/glk: Program dphy param reg for GLK

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

On Mon, 02 Jan 2017, Madhav Chauhan <madhav.chauhan@intel.com> wrote:
> From: Deepak M <m.deepak@intel.com>
>
> For GEMINILAKE, dphy param reg values are programmed in terms
> of HS byte clock count while for legacy platforms in terms of
> HS ddr clk count.

No need to call everything before this one "legacy".

> Signed-off-by: Deepak M <m.deepak@intel.com>
> Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dsi_panel_vbt.c | 33 +++++++++++++++++++++++-------
>  1 file changed, 26 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> index 8f683b8..8059cbb 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> @@ -695,16 +695,26 @@ struct drm_panel *vbt_panel_init(struct intel_dsi *intel_dsi, u16 panel_id)
>  	/* count values in UI = (ns value) * (bitrate / (2 * 10^6))
>  	 *
>  	 * Since txddrclkhs_i is 2xUI, all the count values programmed in
> -	 * DPHY param register are divided by 2
> +	 * DPHY param register are divided by 2 except GEMINILAKE where it is
> +	 * programmed in terms of HS byte clock so divided by 8

Would you say these two hold?

1) HSDDR = 2 * HS

2) HS byte clock = HS / 8

So it would seem to me either the existing code or your patch is
wrong. (Or I'm seriously confused.)

If the register is in terms of clock *cycles*, not frequency, should the
HSDDR based clock (pre-GLK) actually have *twice* the clock cycles, not
*half*? Making the existing code wrong?

The existing code could use some serious cleanup to make it readable. :(

BR,
Jani.



>  	 *
>  	 * prepare count
>  	 */
>  	ths_prepare_ns = max(mipi_config->ths_prepare,
>  			     mipi_config->tclk_prepare);
> -	prepare_cnt = DIV_ROUND_UP(ths_prepare_ns * ui_den, ui_num * 2);
> +	if (IS_GEMINILAKE(dev_priv))
> +		prepare_cnt = DIV_ROUND_UP(ths_prepare_ns * ui_den, ui_num * 8);
> +	else
> +		prepare_cnt = DIV_ROUND_UP(ths_prepare_ns * ui_den, ui_num * 2);
>  
>  	/* exit zero count */
> -	exit_zero_cnt = DIV_ROUND_UP(
> +	if (IS_GEMINILAKE(dev_priv))
> +		exit_zero_cnt = DIV_ROUND_UP(
> +				(ths_prepare_hszero - ths_prepare_ns) * ui_den,
> +				ui_num * 8
> +				);
> +	else
> +		exit_zero_cnt = DIV_ROUND_UP(
>  				(ths_prepare_hszero - ths_prepare_ns) * ui_den,
>  				ui_num * 2
>  				);
> @@ -719,13 +729,22 @@ struct drm_panel *vbt_panel_init(struct intel_dsi *intel_dsi, u16 panel_id)
>  		exit_zero_cnt += 1;
>  
>  	/* clk zero count */
> -	clk_zero_cnt = DIV_ROUND_UP(
> -			(tclk_prepare_clkzero -	ths_prepare_ns)
> -			* ui_den, 2 * ui_num);
> +	if (IS_GEMINILAKE(dev_priv))
> +		clk_zero_cnt = DIV_ROUND_UP(
> +				(tclk_prepare_clkzero -	ths_prepare_ns)
> +				* ui_den, 8 * ui_num);
> +	else
> +		clk_zero_cnt = DIV_ROUND_UP(
> +				(tclk_prepare_clkzero -	ths_prepare_ns)
> +				* ui_den, 2 * ui_num);
>  
>  	/* trail count */
>  	tclk_trail_ns = max(mipi_config->tclk_trail, mipi_config->ths_trail);
> -	trail_cnt = DIV_ROUND_UP(tclk_trail_ns * ui_den, 2 * ui_num);
> +
> +	if (IS_GEMINILAKE(dev_priv))
> +		trail_cnt = DIV_ROUND_UP(tclk_trail_ns * ui_den, 8 * ui_num);
> +	else
> +		trail_cnt = DIV_ROUND_UP(tclk_trail_ns * ui_den, 2 * ui_num);
>  
>  	if (prepare_cnt > PREPARE_CNT_MAX ||
>  		exit_zero_cnt > EXIT_ZERO_CNT_MAX ||

-- 
Jani Nikula, Intel Open Source Technology Center
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