[Intel-gfx] [PATCH] [i915] add module param "enable_dp_mst"

[Daniel Vetter]

On Mon, Mar 14, 2016 at 11:36:29AM -0500, Nathan Schulte wrote:
> Adds an (unsafe; auto-kernel-tainting) boolean module parameter to the i915
> drm driver: "enable_dp_mst", which is enabled by default.  Disabling the
> parameter forces newly connected DisplayPort sinks to report as not
> supporting multi-stream transport (MST), thus "forcing" the use of
> single-stream transport (SST).

Patch itself looks good, but you're missing the s-o-b line per
Documentation/SubmittingPatches, "developers certificate of origin". I
need that before I can apply it.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_params.c | 5 +++++
>  drivers/gpu/drm/i915/i915_params.h | 1 +
>  drivers/gpu/drm/i915/intel_dp.c    | 3 +++
>  3 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 278c9c4..97691f1 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -56,6 +56,7 @@ struct i915_params i915 __read_mostly = {
>  	.edp_vswing = 0,
>  	.enable_guc_submission = false,
>  	.guc_log_level = -1,
> +	.enable_dp_mst = true,
>  };
>  
>  module_param_named(modeset, i915.modeset, int, 0400);
> @@ -201,3 +202,7 @@ MODULE_PARM_DESC(enable_guc_submission, "Enable GuC submission (default:false)")
>  module_param_named(guc_log_level, i915.guc_log_level, int, 0400);
>  MODULE_PARM_DESC(guc_log_level,
>  	"GuC firmware logging level (-1:disabled (default), 0-3:enabled)");
> +
> +module_param_named_unsafe(enable_dp_mst, i915.enable_dp_mst, bool, 0600);
> +MODULE_PARM_DESC(enable_dp_mst,
> +	"Enable multi-stream transport (MST) for new DisplayPort sinks. (default: true)");
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index bd5026b..87153b0 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -59,6 +59,7 @@ struct i915_params {
>  	bool enable_guc_submission;
>  	bool verbose_state_checks;
>  	bool nuclear_pageflip;
> +	bool enable_dp_mst;
>  };
>  
>  extern struct i915_params i915 __read_mostly;
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 0e326e7..ba2d024 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3882,6 +3882,9 @@ intel_dp_probe_mst(struct intel_dp *intel_dp)
>  {
>  	u8 buf[1];
>  
> +	if (!i915.enable_dp_mst)
> +		return false;
> +
>  	if (!intel_dp->can_mst)
>  		return false;
>  
> -- 
> 2.7.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch