Re: [PATCH] drm/i915: Changes required to enable DSI Video Mode on CHT

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

On Wed, 10 Dec 2014, Gaurav K Singh <gaurav.k.singh@intel.com> wrote:
> For CHT changes are required for calculating the correct m,n & p with
> minimal error +/- for the required DSI clock, so that the correct dividor
> & ctrl values are written in cck regs for DSI. This patch has been tested
> on CHT RVP with 1200 x 1920 panel.
>
> Signed-off-by: Gaurav K Singh <gaurav.k.singh@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dsi_pll.c |   43 ++++++++++++++++++++++++++--------
>  1 file changed, 33 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
> index 8957f10..9236b66 100644
> --- a/drivers/gpu/drm/i915/intel_dsi_pll.c
> +++ b/drivers/gpu/drm/i915/intel_dsi_pll.c
> @@ -162,7 +162,8 @@ static u32 dsi_clk_from_pclk(u32 pclk, int pixel_format, int lane_count)
>  
>  #endif
>  
> -static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
> +static int dsi_calc_mnp(struct drm_i915_private *dev_priv,
> +			u32 dsi_clk, struct dsi_mnp *dsi_mnp)
>  {
>  	u32 m, n, p;
>  	u32 ref_clk;
> @@ -173,6 +174,10 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
>  	u32 calc_m;
>  	u32 calc_p;
>  	u32 m_seed;
> +	u32 m_start;
> +	u32 m_limit;
> +	u32 n_limit;
> +	u32 p_limit;
>  
>  	/* dsi_clk is expected in KHZ */
>  	if (dsi_clk < 300000 || dsi_clk > 1150000) {
> @@ -180,18 +185,33 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
>  		return -ECHRNG;
>  	}
>  
> -	ref_clk = 25000;
> +	if (IS_CHERRYVIEW(dev_priv->dev)) {

You can use IS_CHERRYVIEW(dev_priv) directly. It's magic.

> +		ref_clk = 100000;
> +		m_start = 70;
> +		m_limit = 96;
> +		n_limit = 4;
> +		p_limit = 6;
> +	} else if (IS_VALLEYVIEW(dev_priv->dev)) {

Same.

> +		ref_clk = 25000;
> +		m_start = 62;
> +		m_limit = 92;
> +		n_limit = 1;
> +		p_limit = 6;
> +	} else {
> +		DRM_ERROR("Unsupported device\n");
> +		return -ENODEV;
> +	}

We don't really do this kind of else branches, otherwise the driver
would be full of it.

Otherwise,

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


>  	target_dsi_clk = dsi_clk;
>  	error = 0xFFFFFFFF;
>  	tmp_error = 0xFFFFFFFF;
>  	calc_m = 0;
>  	calc_p = 0;
>  
> -	for (m = 62; m <= 92; m++) {
> -		for (p = 2; p <= 6; p++) {
> +	for (m = m_start; m <= m_limit; m++) {
> +		for (p = 2; p <= p_limit; p++) {
>  			/* Find the optimal m and p divisors
>  			   with minimal error +/- the required clock */
> -			calc_dsi_clk = (m * ref_clk) / p;
> +			calc_dsi_clk = (m * ref_clk) / (p * n_limit);
>  			if (calc_dsi_clk == target_dsi_clk) {
>  				calc_m = m;
>  				calc_p = p;
> @@ -212,11 +232,14 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
>  	}
>  
>  	m_seed = lfsr_converts[calc_m - 62];
> -	n = 1;
> +	n = n_limit;
>  	dsi_mnp->dsi_pll_ctrl = 1 << (DSI_PLL_P1_POST_DIV_SHIFT + calc_p - 2);
> -	dsi_mnp->dsi_pll_div = (n - 1) << DSI_PLL_N1_DIV_SHIFT |
> -		m_seed << DSI_PLL_M1_DIV_SHIFT;
> -
> +	if (IS_CHERRYVIEW(dev_priv->dev))
> +		dsi_mnp->dsi_pll_div = (n/2) << DSI_PLL_N1_DIV_SHIFT |
> +				m_seed << DSI_PLL_M1_DIV_SHIFT;
> +	else
> +		dsi_mnp->dsi_pll_div = (n - 1) << DSI_PLL_N1_DIV_SHIFT |
> +				m_seed << DSI_PLL_M1_DIV_SHIFT;
>  	return 0;
>  }
>  
> @@ -235,7 +258,7 @@ static void vlv_configure_dsi_pll(struct intel_encoder *encoder)
>  	dsi_clk = dsi_clk_from_pclk(intel_dsi->pclk, intel_dsi->pixel_format,
>  				    intel_dsi->lane_count);
>  
> -	ret = dsi_calc_mnp(dsi_clk, &dsi_mnp);
> +	ret = dsi_calc_mnp(dev_priv, dsi_clk, &dsi_mnp);
>  	if (ret) {
>  		DRM_DEBUG_KMS("dsi_calc_mnp failed\n");
>  		return;
> -- 
> 1.7.9.5
>
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center
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