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

["Singh, Gaurav K" <gaurav.k.singh@intel.com>]

On 12/10/2014 7:38 PM, Gaurav K Singh 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)) {
> +		ref_clk = 100000;
> +		m_start = 70;
> +		m_limit = 96;
> +		n_limit = 4;
> +		p_limit = 6;
> +	} else if (IS_VALLEYVIEW(dev_priv->dev)) {
> +		ref_clk = 25000;
> +		m_start = 62;
> +		m_limit = 92;
> +		n_limit = 1;
> +		p_limit = 6;
> +	} else {
> +		DRM_ERROR("Unsupported device\n");
> +		return -ENODEV;
> +	}
>   	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;
Hi Jani,

Could you please review this patch?

With regards,
Gaurav

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