Re: [PATCH 2/4] drm/i915: go back to switch for VLV mem freq detection v2

[Ben Widawsky <ben@bwidawsk.net>]

On Thu, May 02, 2013 at 10:48:08AM -0700, Jesse Barnes wrote:
> Both the docs and the existing code were wrong.  So fix both and use a
> switch statement like we do elsewhere to make things simple & clear.
> 
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/intel_pm.c |   13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 0f4b46e..556b989 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2902,7 +2902,18 @@ static void valleyview_enable_rps(struct drm_device *dev)
>  		   GEN7_RC_CTL_TO_MODE);
>  
>  	valleyview_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS, &val);
> -	dev_priv->mem_freq = 800 + (266 * (val >> 6) & 3);
> +	switch ((val >> 6) & 3) {
> +	case 0:
> +	case 1:
> +		dev_priv->mem_freq = 800;
> +		break;
> +	case 2:
> +		dev_priv->mem_freq = 1066;
> +		break;
> +	case 3:
> +		dev_priv->mem_freq = 1333;
> +		break;
> +	}
>  	DRM_DEBUG_DRIVER("DDR speed: %d MHz", dev_priv->mem_freq);
>  
>  	DRM_DEBUG_DRIVER("GPLL enabled? %s\n", val & 0x10 ? "yes" : "no");

The code does what the author wants it to, but I don't have the doc that
says this:
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

Since I've set up a precedent of providing what I think are better
options:
freq_lut[] = {800, 800, 1066, 1333};
freq_lut[(val >> 6) & 3];

[really ugly one-liner redacted]

-- 
Ben Widawsky, Intel Open Source Technology Center