Re: [PATCH] drm/i915/vlv: add VLV specific clock_get function v3

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Sep 20, 2013 at 11:29:32AM -0700, Jesse Barnes wrote:
> Calculation is a little different than other platforms.
> 
> v2: update to use port_clock instead
>     rebase on top of Ville's changes
> v3: update to new port_clock semantics - don't divide by
>     pixel_multiplier (Ville)
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=67345
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/intel_display.c |   33 ++++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7eecf37..e5c9c1c 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5048,6 +5048,34 @@ static void i9xx_get_pfit_config(struct intel_crtc *crtc,
>  			I915_READ(LVDS) & LVDS_BORDER_ENABLE;
>  }
>  
> +static void vlv_crtc_clock_get(struct intel_crtc *crtc,
> +			       struct intel_crtc_config *pipe_config)
> +{
> +	struct drm_device *dev = crtc->base.dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	int pipe = pipe_config->cpu_transcoder;
> +	intel_clock_t clock;
> +	u32 mdiv;
> +	int refclk = 100000, fastclk, update_rate;
> +
> +	mutex_lock(&dev_priv->dpio_lock);
> +	mdiv = vlv_dpio_read(dev_priv, pipe, DPIO_DIV(pipe));
> +	mutex_unlock(&dev_priv->dpio_lock);
> +
> +	clock.m1 = (mdiv >> DPIO_M1DIV_SHIFT) & 7;
> +	clock.m2 = mdiv & DPIO_M2DIV_MASK;
> +	clock.n = (mdiv >> DPIO_N_SHIFT) & 0xf;
> +	clock.p1 = (mdiv >> DPIO_P1_SHIFT) & 7;
> +	clock.p2 = (mdiv >> DPIO_P2_SHIFT) & 0x1f;
> +
> +	update_rate = refclk / clock.n;
> +	clock.vco = update_rate * clock.m1 * clock.m2;
> +	fastclk = clock.vco / clock.p1 / clock.p2;
> +	clock.dot = (2 * fastclk);
> +
> +	pipe_config->port_clock = clock.dot / 10;

Looks like it should get roughly the right answer, but I don't see much
point in all the intermediate results.

If you want to keep some of them for clarity, then I think this should
be enough:

clock.vco = refclk * clock.m / clock.n;
clock.dot = clock.vco / clock.p; /* fast clock */
pipe_config->port_clock = clock.dot / 5;

Although calling the fast clock "dot" is a bit wrong, but I think it's
fine here, especially as it matches what I have in mind for
vlv_find_best_dpll(). I had to rewrite that sucker a bit to make it
compatible with my brain ;) I'll send a patch for that ASAP.

> +}
> +
>  static bool i9xx_get_pipe_config(struct intel_crtc *crtc,
>  				 struct intel_crtc_config *pipe_config)
>  {
> @@ -5113,7 +5141,10 @@ static bool i9xx_get_pipe_config(struct intel_crtc *crtc,
>  						     DPLL_PORTB_READY_MASK);
>  	}
>  
> -	i9xx_crtc_clock_get(crtc, pipe_config);
> +	if (IS_VALLEYVIEW(dev))
> +		vlv_crtc_clock_get(crtc, pipe_config);
> +	else
> +		i9xx_crtc_clock_get(crtc, pipe_config);
>  
>  	return true;
>  }
> -- 
> 1.7.9.5
> 
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-- 
Ville Syrjälä
Intel OTC