Re: [PATCH] drm/i915/cnl: Fix DP max voltage

Ville Syrjälä
2017-08-31T12:34:39Z

On Wed, Aug 30, 2017 at 05:00:50PM -0700, Rodrigo Vivi wrote:
> From: "Vivi, Rodrigo" <rodrigo.vivi@intel.com>
>
> On clock recovery this function is called to find out
> the max voltage swing level that we could go.
>
> However gen 9 functions use the old buffer translation tables
> to figure that out. That table is not valid for CNL
> causing an invalid number of entries and an invalid selection
> on the max voltage swing level.
>
> v2: Let's use same approach that previous platforms.
> v3: Actually use n_entries and avoid duplicated -1.
>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Clint Taylor <clinton.a.taylor@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
> drivers/gpu/drm/i915/intel_ddi.c | 48 +++++++++++++++++++++++++++++++---------
> 1 file changed, 38 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index d962552e2ccc..9aa508616284 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -649,6 +649,29 @@ cnl_get_buf_trans_edp(struct drm_i915_private *dev_priv, int *n_entries)
> }
> }
>
> +static int cnl_max_level(struct drm_i915_private *dev_priv,
> + enum intel_output_type type)
> +{
> + int n_entries = 0;
> +
> + switch (type) {
> + case INTEL_OUTPUT_DP:
> + cnl_get_buf_trans_dp(dev_priv, &n_entries);
> + break;
> + case INTEL_OUTPUT_EDP:
> + cnl_get_buf_trans_edp(dev_priv, &n_entries);
> + break;
> + case INTEL_OUTPUT_HDMI:
> + cnl_get_buf_trans_hdmi(dev_priv, &n_entries);
> + break;
> + default:
> + MISSING_CASE(type);
> + return 0;
> + }
> +
> + return n_entries;
> +}
> +
> static int intel_ddi_hdmi_level(struct drm_i915_private *dev_priv, enum port port)
> {
> int n_hdmi_entries;
> @@ -1877,19 +1900,24 @@ static void bxt_ddi_vswing_sequence(struct drm_i915_private *dev_priv,
> u8 intel_ddi_dp_voltage_max(struct intel_encoder *encoder)
> {
> struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> - int n_entries;
> + int n_entries, level;
>
> - if (encoder->type == INTEL_OUTPUT_EDP)
> - intel_ddi_get_buf_trans_edp(dev_priv, &n_entries);
> - else
> - intel_ddi_get_buf_trans_dp(dev_priv, &n_entries);
> + if (IS_CANNONLAKE(dev_priv)) {
> + level = cnl_max_level(dev_priv, encoder->type);
> + } else {
> + if (encoder->type == INTEL_OUTPUT_EDP)
> + intel_ddi_get_buf_trans_edp(dev_priv, &n_entries);
> + else
> + intel_ddi_get_buf_trans_dp(dev_priv, &n_entries);
> + level = n_entries - 1;

You removed the -1 from the cnl path but then added it to the other path?

In fact, I think to keep things looking a bit more consistent I'd just
open code the cnl stuff in intel_ddi_dp_voltage_max() the same way as
the other platforms are handled. And we don't even need to care about HDMI
here.

> + }
>
> - if (WARN_ON(n_entries < 1))
> - n_entries = 1;
> - if (WARN_ON(n_entries > ARRAY_SIZE(index_to_dp_signal_levels)))
> - n_entries = ARRAY_SIZE(index_to_dp_signal_levels);
> + if (WARN_ON(level < 0))
> + level = 0;
> + if (WARN_ON(level > ARRAY_SIZE(index_to_dp_signal_levels) - 1))
> + level = ARRAY_SIZE(index_to_dp_signal_levels) - 1;
>
> - return index_to_dp_signal_levels[n_entries - 1] &
> + return index_to_dp_signal_levels[level] &
> DP_TRAIN_VOLTAGE_SWING_MASK;
> }
>
> --
> 2.13.2

--
Ville Syrjälä
Intel OTC