Re: [PATCH] drm/i915: vlv: clamp minimum RPS frequency to what Punit allows

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

On Thu, Dec 04, 2014 at 06:39:35PM +0200, Imre Deak wrote:
> As described in the code comment, I couldn't set the minimum RPS
> frequency on my BYT-M B0 to the minimum allowed as reported by Punit.
> Fix this by clamping the minimum value to the first one that was
> accepted on my machine. This fixes at least the pm_rpm basic-api and
> min-max-config subtests.
> 
> Testcase: igt/pm_rps
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 45c786f..7a1112f 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -5039,7 +5039,17 @@ static int valleyview_rps_rpe_freq(struct drm_i915_private *dev_priv)
>  
>  static int valleyview_rps_min_freq(struct drm_i915_private *dev_priv)
>  {
> -	return vlv_punit_read(dev_priv, PUNIT_REG_GPU_LFM) & 0xff;
> +	u32 val;
> +
> +	val = vlv_punit_read(dev_priv, PUNIT_REG_GPU_LFM) & 0xff;
> +	/*
> +	 * According to the BYT Punit GPU turbo HAS 1.1.6.3 the minimum value
> +	 * for the minimum frequency in GPLL mode is 0xc1. Contrary to this on
> +	 * a BYT-M B0 the above register contains 0xbf. Moreover when setting
> +	 * a frequency Punit will not allow values below 0xc0. Clamp it 0xc0
> +	 * to make sure it matches what Punit accepts.
> +	 */
> +	return max_t(u32, val, 0xc0);

Matches what I see on this ffrd as well. But this too has czclk==266.
Would be interesting to see what happens with other czclks. Anyone
have a byt w/ 1333 memory?

>  }
>  
>  /* Check that the pctx buffer wasn't move under us. */
> -- 
> 1.8.4
> 
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-- 
Ville Syrjälä
Intel OTC
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