Re: [PATCH 6/6] drm/i915: Use DIV_ROUND_CLOSEST for PWM calculations

Jani Nikula
2016-03-03T08:25:09Z

On Wed, 02 Mar 2016, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Supposedly we would want to get the PWM output as close as possible to
> the target, so let's round to closest.
>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Suggested-by: Jani Nikula <jani.nikula@linux.intel.com>

I have zero recollection of asking this change, but since it makes sense
I won't deny it was me.

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

> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_panel.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 5cf377507162..0fe059bc7d80 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1240,7 +1240,7 @@ static void intel_backlight_device_unregister(struct intel_connector *connector)
> */
> static u32 bxt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> {
> - return KHz(19200) / pwm_freq_hz;
> + return DIV_ROUND_CLOSEST(KHz(19200), pwm_freq_hz);
> }
>
> /*
> @@ -1258,7 +1258,7 @@ static u32 spt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> else
> mul = 16;
>
> - return MHz(24) / (pwm_freq_hz * mul);
> + return DIV_ROUND_CLOSEST(MHz(24), pwm_freq_hz * mul);
> }
>
> /*
> @@ -1281,7 +1281,7 @@ static u32 lpt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> else
> clock = MHz(24); /* LPT:LP */
>
> - return clock / (pwm_freq_hz * mul);
> + return DIV_ROUND_CLOSEST(clock, pwm_freq_hz * mul);
> }
>
> /*
> @@ -1292,7 +1292,7 @@ static u32 pch_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> {
> struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>
> - return KHz(dev_priv->rawclk_freq) / (pwm_freq_hz * 128);
> + return DIV_ROUND_CLOSEST(KHz(dev_priv->rawclk_freq), pwm_freq_hz * 128);
> }
>
> /*
> @@ -1313,7 +1313,7 @@ static u32 i9xx_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> else
> clock = KHz(dev_priv->cdclk_freq);
>
> - return clock / (pwm_freq_hz * 32);
> + return DIV_ROUND_CLOSEST(clock, pwm_freq_hz * 32);
> }
>
> /*
> @@ -1332,7 +1332,7 @@ static u32 i965_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> else
> clock = KHz(dev_priv->cdclk_freq);
>
> - return clock / (pwm_freq_hz * 128);
> + return DIV_ROUND_CLOSEST(clock, pwm_freq_hz * 128);
> }
>
> /*
> @@ -1356,7 +1356,7 @@ static u32 vlv_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
> mul = 128;
> }
>
> - return clock / (pwm_freq_hz * mul);
> + return DIV_ROUND_CLOSEST(clock, pwm_freq_hz * mul);
> }
>
> static u32 get_backlight_max_vbt(struct intel_connector *connector)

--
Jani Nikula, Intel Open Source Technology Center