Re: [stable:v4.15] drm/i915/dp: Write to SET_POWER dpcd to enable MST hub.

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

DK, please start stable backport commit messages with:

commit b1e314462bba76660eec62760bb2e87f28f58866 upstream.

Referencing the upstream commit.

BR,
Jani.


On Thu, 29 Mar 2018, Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> wrote:
> If bios sets up an MST output and hardware state readout code sees this is
> an SST configuration, when disabling the encoder we end up calling
> ->post_disable_dp() hook instead of the MST version. Consequently, we write
> to the DP_SET_POWER dpcd to set it D3 state. Further along when we try
> enable the encoder in MST mode, POWER_UP_PHY transaction fails to power up
> the MST hub. This results in continuous link training failures which keep
> the system busy delaying boot. We could identify bios MST boot discrepancy
> and handle it accordingly but a simple way to solve this is to write to the
> DP_SET_POWER dpcd for MST too.
>
> v2: Rebased on stable/linux-4.15.y and fixed minor conflict.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105470
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Reported-by: Laura Abbott <labbott@redhat.com>
> Cc: <stable@vger.kernel.org> # 4.15+
> Fixes: 5ea2355a100a ("drm/i915/mst: Use MST sideband message transactions for dpms control")
> Tested-by: Laura Abbott <labbott@redhat.com>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> Link: https://patchwork.freedesktop.org/patch/msgid/20180314054825.1718-1-dhinakaran.pandiyan@intel.com
> (cherry picked from commit ad260ab32a4d94fa974f58262f8000472d34fd5b)
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 58a3755544b2..38e53d6b8127 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2208,8 +2208,7 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  		intel_prepare_dp_ddi_buffers(encoder);
>  
>  	intel_ddi_init_dp_buf_reg(encoder);
> -	if (!is_mst)
> -		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> +	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
>  	intel_dp_start_link_train(intel_dp);
>  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>  		intel_dp_stop_link_train(intel_dp);
> @@ -2294,19 +2293,12 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>  	struct intel_digital_port *dig_port = enc_to_dig_port(&encoder->base);
>  	struct intel_dp *intel_dp = &dig_port->dp;
> -	/*
> -	 * old_crtc_state and old_conn_state are NULL when called from
> -	 * DP_MST. The main connector associated with this port is never
> -	 * bound to a crtc for MST.
> -	 */
> -	bool is_mst = !old_crtc_state;
>  
>  	/*
>  	 * Power down sink before disabling the port, otherwise we end
>  	 * up getting interrupts from the sink on detecting link loss.
>  	 */
> -	if (!is_mst)
> -		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
> +	intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
>  
>  	intel_disable_ddi_buf(encoder);

-- 
Jani Nikula, Intel Open Source Technology Center
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