Re: [PATCH] drm/i915/cnl: Respect VBT max dp rate.

[Jani Nikula <jani.nikula@intel.com>]

On Wed, 31 Jan 2018, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
> Since commit 'c4fb60b9aba9 ("drm/i915/bios: add DP max link
> rate to VBT child device struct")' we have the new entry
> defined for max dp rate that is in use for CNL.
>
> Let's start using it for all VBT 216+ and
> also organize the cnl adjusted rates in terms of rate
> and not array size.

Rodrigo, I took the liberty of rewriting this into three patches [1]. I
hope you don't mind. I had some of this in mind way back when I rewrote
the source/sink rate handling.

Some notes inline below. I've taken them into account in my series.

BR,
Jani.


[1] http://patchwork.freedesktop.org/patch/msgid/40f37f08cad33234cd86337d39e823ac6e55805f.1517482774.git.jani.nikula@intel.com


>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h   |  1 +
>  drivers/gpu/drm/i915/intel_bios.c |  3 +++
>  drivers/gpu/drm/i915/intel_dp.c   | 37 +++++++++++++++++++++++++++++--------
>  3 files changed, 33 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index c676269ed843..66dea5c9b10e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1282,6 +1282,7 @@ struct ddi_vbt_port_info {
>  
>  	uint8_t dp_boost_level;
>  	uint8_t hdmi_boost_level;
> +	uint8_t dp_max_link_rate;
>  };
>  
>  enum psr_lines_to_wait {
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index cf3f8f1ba6f7..c885daf4cc8d 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -1230,6 +1230,9 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
>  		info->alternate_aux_channel = aux_channel;
>  
>  		sanitize_aux_ch(dev_priv, port);
> +
> +		if (bdb_version >= 216 && child->dp_max_link_rate)
> +			info->dp_max_link_rate = child->dp_max_link_rate;

The info is two bits in VBT and needs to be translated to rates.

>  	}
>  
>  	if (bdb_version >= 158) {
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 03d86ff9b805..1e34d7954355 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -220,7 +220,7 @@ intel_dp_downstream_max_dotclock(struct intel_dp *intel_dp)
>  	return max_dotclk;
>  }
>  
> -static int cnl_adjusted_max_rate(struct intel_dp *intel_dp, int size)
> +static int cnl_adjusted_max_rate(struct intel_dp *intel_dp)
>  {
>  	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
>  	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
> @@ -230,17 +230,33 @@ static int cnl_adjusted_max_rate(struct intel_dp *intel_dp, int size)
>  
>  	/* Low voltage SKUs are limited to max of 5.4G */
>  	if (voltage == VOLTAGE_INFO_0_85V)
> -		return size - 2;
> +		return 540000;
>  
>  	/* For this SKU 8.1G is supported in all ports */
>  	if (IS_CNL_WITH_PORT_F(dev_priv))
> -		return size;
> +		return 810000;
>  
>  	/* For other SKUs, max rate on ports A and B is 5.4G */
>  	if (port == PORT_A || port == PORT_D)
> -		return size - 2;
> +		return 540000;
>  
> -	return size;
> +	return 810000;
> +}
> +
> +static int intel_dp_adjusted_max_rate(struct intel_dp *intel_dp)
> +{
> +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> +	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
> +	const struct ddi_vbt_port_info *info =
> +		&dev_priv->vbt.ddi_port_info[dig_port->base.port];
> +
> +	if (info->dp_max_link_rate)
> +		return info->dp_max_link_rate;

The VBT value needs mapping, and 0 actually means HBR3 in VBT.

> +
> +	if (IS_CANNONLAKE(dev_priv))
> +		return cnl_adjusted_max_rate(intel_dp);

Like DK noted, I think this should be a min() of the two.

> +
> +	return INT_MAX; /* No adjusted limit */

I really want functions like this to return the actual max rate. I think
returning INT_MAX here is a bit scary.

>  }
>  
>  static void
> @@ -249,7 +265,8 @@ intel_dp_set_source_rates(struct intel_dp *intel_dp)
>  	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
>  	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
>  	const int *source_rates;
> -	int size;
> +	int i, size;
> +	int max_rate = intel_dp_adjusted_max_rate(intel_dp);
>  
>  	/* This should only be done once */
>  	WARN_ON(intel_dp->source_rates || intel_dp->num_source_rates);
> @@ -259,7 +276,7 @@ intel_dp_set_source_rates(struct intel_dp *intel_dp)
>  		size = ARRAY_SIZE(bxt_rates);
>  	} else if (IS_CANNONLAKE(dev_priv)) {
>  		source_rates = cnl_rates;
> -		size = cnl_adjusted_max_rate(intel_dp, ARRAY_SIZE(cnl_rates));
> +		size = ARRAY_SIZE(cnl_rates);
>  	} else if (IS_GEN9_BC(dev_priv)) {
>  		source_rates = skl_rates;
>  		size = ARRAY_SIZE(skl_rates);
> @@ -272,8 +289,12 @@ intel_dp_set_source_rates(struct intel_dp *intel_dp)
>  		size = ARRAY_SIZE(default_rates) - 1;
>  	}
>  
> +	for (i = 0; i < size; i++)
> +		if (source_rates[i] > max_rate)
> +			break;

We already have code to do this stuff, so I refactored and reused it.

> +
> +	intel_dp->num_source_rates = i;
>  	intel_dp->source_rates = source_rates;
> -	intel_dp->num_source_rates = size;
>  }
>  
>  static int intersect_rates(const int *source_rates, int source_len,

-- 
Jani Nikula, Intel Open Source Technology Center
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