[PATCH 11/12] drm/dp: Read AUX read interval from DPCD

[Daniel Vetter]

On Mon, Dec 14, 2015 at 01:56:03PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
> 
> Store the AUX read interval from DPCD, so that it can be used to wait
> for the durations given in the specification during link training.
> 
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c |  4 ++++
>  include/drm/drm_dp_helper.h     | 17 +++++++++++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 76ac68bc1042..da519acfeba7 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -339,6 +339,7 @@ static void drm_dp_link_reset(struct drm_dp_link *link)
>  	link->max_lanes = 0;
>  
>  	drm_dp_link_caps_reset(&link->caps);
> +	link->aux_rd_interval = 0;
>  	link->edp = 0;
>  
>  	link->rate = 0;
> @@ -392,6 +393,9 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
>  			link->edp = edp_revs[value];
>  	}
>  
> +	/* DP_TRAINING_AUX_RD_INTERVAL is in units of 4 milliseconds */
> +	link->aux_rd_interval = drm_dp_aux_rd_interval(values);

Hm, just wondering a bit of the relationship between link and cap. Is link
all about sink really, and not the source? At least in my experience it
makes a lot of sense to strictly keep these two separate, since otherwise
you'll have lots of fun aligning things in generic code. Anyway, just a
thougth.

> +
>  	link->rate = link->max_rate;
>  	link->lanes = link->max_lanes;
>  
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 825aaf4e8c71..20ae0e413b64 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -678,6 +678,22 @@ drm_dp_alternate_scrambler_reset_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
>  			DP_ALTERNATE_SCRAMBLER_RESET_CAP;
>  }
>  
> +/**
> + * drm_dp_read_aux_interval() - read the AUX read interval from the DPCD
> + * @dpcd: receiver capacity buffer
> + *
> + * Reads the AUX read interval (in microseconds) from the DPCD. Note that the
> + * TRAINING_AUX_RD_INTERVAL stores the value in units of 4 milliseconds.
> + *
> + * Returns:
> + * The read AUX interval in microseconds.
> + */
> +static inline unsigned int
> +drm_dp_aux_rd_interval(const u8 dpcd[DP_RECEIVER_CAP_SIZE])

We should use this one here in the 2 delay helpers for channel_eq and
clock_recovery imo.
-Daniel

> +{
> +	return dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4000;
> +}
> +
>  /*
>   * DisplayPort AUX channel
>   */
> @@ -805,6 +821,7 @@ struct drm_dp_link {
>  	unsigned int max_lanes;
>  
>  	struct drm_dp_link_caps caps;
> +	unsigned int aux_rd_interval;
>  	unsigned char edp;
>  
>  	unsigned int rate;
> -- 
> 2.5.0
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch