Re: [PATCH 7/7] drm/i915/dp: Enable Upfront link training for typeC DP support on BXT

From: Ander Conselvan De Oliveira <conselvan2@gmail.com>
To: "R, Durgadoss" <durgadoss.r@intel.com>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 7/7] drm/i915/dp: Enable Upfront link training for typeC DP support on BXT
Date: Mon, 11 Jan 2016 16:10:05 +0200	[thread overview]
Message-ID: <1452521405.2737.21.camel@gmail.com> (raw)
In-Reply-To: <4D68720C2E767A4AA6A8796D42C8EB5909363938@BGSMSX101.gar.corp.intel.com>

On Tue, 2015-12-29 at 18:50 +0000, R, Durgadoss wrote:
> Hi Ander,
> 
> Thanks for looking into this..
> 
> > -----Original Message-----
> > From: Ander Conselvan De Oliveira [mailto:conselvan2@gmail.com]
> > Sent: Tuesday, December 29, 2015 10:52 PM
> > To: R, Durgadoss; intel-gfx@lists.freedesktop.org
> > Subject: Re: [PATCH 7/7] drm/i915/dp: Enable Upfront link training for typeC
> > DP support on BXT
> > 
> > On Fri, 2015-12-11 at 15:09 +0530, Durgadoss R wrote:
> > > To support USB type C alternate DP mode, the display driver needs to
> > > know the number of lanes required by the DP panel as well as number
> > > of lanes that can be supported by the type-C cable. Sometimes, the
> > > type-C cable may limit the bandwidth even if Panel can support
> > > more lanes. To address these scenarios, the display driver will
> > > start link training with max lanes, and if that fails, the driver
> > > falls back to x2 lanes; and repeats this procedure for all
> > > bandwidth/lane configurations.
> > > 
> > > * Since link training is done before modeset only the port
> > >   (and not pipe/planes) and its associated PLLs are enabled.
> > > * On DP hotplug: Directly start link training on the crtc
> > >   associated with the DP encoder.
> > > * On Connected boot scenarios: When booted with an LFP and a DP,
> > >   typically, BIOS brings up DP. In these cases, we disable the
> > >   crtc, do upfront link training and then re-enable it back.
> > > * All local changes made for upfront link training are reset
> > >   to their previous values once it is done; so that the
> > >   subsequent modeset is not aware of these changes.
> > > 
> > > Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_ddi.c | 81
> > > ++++++++++++++++++++++++++++++++++++++++
> > >  drivers/gpu/drm/i915/intel_dp.c  | 77
> > > +++++++++++++++++++++++++++++++++++++-
> > >  drivers/gpu/drm/i915/intel_drv.h |  2 +
> > >  3 files changed, 159 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c
> > > b/drivers/gpu/drm/i915/intel_ddi.c
> > > index 632044a..43efc26 100644
> > > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > > @@ -3274,6 +3274,87 @@ intel_ddi_init_hdmi_connector(struct
> > > intel_digital_port
> > > *intel_dig_port)
> > >  	return connector;
> > >  }
> > > 
> > > +bool intel_ddi_upfront_link_train(struct intel_dp *intel_dp,
> > > +				struct intel_crtc *crtc)
> > > +{
> > > +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> > > +	struct intel_connector *connector = intel_dp->attached_connector;
> > > +	struct intel_encoder *encoder = connector->encoder;
> > > +	struct drm_device *dev = encoder->base.dev;
> > > +	struct drm_i915_private *dev_priv = dev->dev_private;
> > > +	struct intel_shared_dpll *pll;
> > > +	struct drm_crtc *drm_crtc = NULL;
> > > +	struct intel_crtc_state *tmp_crtc_config;
> > > +	struct intel_dpll_hw_state tmp_dpll_hw_state;
> > > +	uint8_t link_bw, lane_count;
> > > +
> > > +	if (!crtc) {
> > > +		drm_crtc = intel_get_unused_crtc(&encoder->base);
> > > +		if (!drm_crtc) {
> > > +			DRM_ERROR("No crtc for upfront link training\n");
> > > +			return false;
> > > +		}
> > > +		encoder->base.crtc = drm_crtc;
> > > +		crtc = to_intel_crtc(drm_crtc);
> > > +	}
> > > +
> > > +	/* Initialize with Max Link rate & lane count supported by panel
> > > */
> > > +	link_bw =  intel_dp->dpcd[DP_MAX_LINK_RATE];
> > > +	lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> > > +
> > > +	/* Save the crtc->config */
> > > +	tmp_crtc_config = crtc->config;
> > 
> > > +	tmp_dpll_hw_state = crtc->config->dpll_hw_state;
> > > +
> > > +	/* Select the shared DPLL to use for this port */
> > > +	intel_get_ddi_pll(dev_priv, dig_port->port, crtc->config)
> > 
> > This reads the current programmed DPLL from the hardware. Is there any
> > reason we
> > can't trust the value that is in crtc->config already? I don't think this
> > code
> > would run before reading out and sanitizing the hardware state.
> 
> I was not sure of what will be the DPLL attached to crtc->config when the
> crtc is found by 'get_unused_crtc' logic. So, we select the DPLL based
> on port again..
> 
> > 
> > > ;
> > > +	pll = intel_crtc_to_shared_dpll(crtc);
> > > +	if (!pll) {
> > > +		DRM_ERROR("Could not get shared DPLL\n");
> > > +		goto exit;
> > > +	}
> > > +	DRM_DEBUG_KMS("Using %s for pipe %c\n", pll->name, pipe_name(crtc
> > > ->pipe));
> > > +
> > > +	do {
> > > +		crtc->config->port_clock =
> > > drm_dp_bw_code_to_link_rate(link_bw);
> > > +		crtc->config->lane_count = lane_count;
> > > +		if (!intel_ddi_pll_select(crtc, crtc->config, encoder,
> > > false))
> > 
> > 
> > > +			goto exit;
> > > +
> > > +		pll->config.crtc_mask |= (1 << crtc->pipe);
> > > +		pll->config.hw_state = crtc->config->dpll_hw_state;
> > > +
> > > +		/* Enable PLL followed by port */
> > > +		intel_enable_shared_dpll(crtc);
> > > +		encoder->pre_enable(encoder);
> > 
> > The pll handling here seems dodgy. Instead of using intel_get_shared_dpll(),
> 
> I initially tried this, but intel_get_shared_dpll() uses crtc_state which is
> not
> set (in outside modeset contexts) thus creating crashes. Specifically, 
> the call to intel_ddi_get_crtc_new_encoder() for broxton code path.
> 
> That’s why I had to create some initial code to not call get_shared_dpll
> If we have valid encoder attached. (patches 1/7 and 2/7 of this series)
> 
> So, If you have suggestions on how to fix this in a neat way,
> I would be happy to try them out.

One idea would be split the part of intel_get_shared_dpll() that needs atomic
interfaces to a separate function. Then it would be possible to add a second
entry point that just takes crtc, encoder and the pll parameters and calls the
logic that doesn't depend on the atomic state.

Then you could move the calls to intel_get_shared_dpll() from *_ddi_pll_select()
to haswell_crtc_compute_clock() so they don't get on the way during upfront link
training, where the new non-atomic entry point is called instead.

Ander

> 
> Thanks,
> Durga
> 
> > this fiddles with pll internals itself. I think this will work for broxton,
> > since it doesn't actually have shared DPLLs (their chosen based on the
> > encoder).
> > It might just work for haswell too since the plls used by DP are not shared.
> > 
> > But to do this cleanly we need the DPLL interface to just give us the right
> > pll.
> > 
> > Ander
> > 
> > 
> > > +
> > > +		/* Check if link training passed; if so update DPCD */
> > > +		if (intel_dp->train_set_valid)
> > > +			intel_dp_update_dpcd_params(intel_dp);
> > > +
> > > +		/* Disable port followed by PLL for next retry/clean up
> > > */
> > > +		encoder->post_disable(encoder);
> > > +		intel_disable_shared_dpll(crtc);
> > > +
> > > +	} while (!intel_dp->train_set_valid &&
> > > +		!intel_dp_get_link_retry_params(&lane_count, &link_bw));
> > > +
> > > +	/* Reset pll state as before */
> > > +	pll->config.crtc_mask &= ~(1 << crtc->pipe);
> > > +	pll->config.hw_state = tmp_dpll_hw_state;
> > > +
> > > +exit:
> > > +	/* Reset local associations made */
> > > +	if (drm_crtc)
> > > +		encoder->base.crtc = NULL;
> > > +	crtc->config = tmp_crtc_config;
> > > +
> > > +	DRM_DEBUG_KMS("Upfront link train %s: lanes:%d bw:%d\n",
> > > +	intel_dp->train_set_valid ? "Passed" : "Failed", lane_count,
> > > link_bw);
> > > +
> > > +	return intel_dp->train_set_valid;
> > > +}
> > > +
> > >  void intel_ddi_init(struct drm_device *dev, enum port port)
> > >  {
> > >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > > b/drivers/gpu/drm/i915/intel_dp.c
> > > index d8f7830..47b6266 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -4622,6 +4622,71 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
> > >  	intel_dp->has_audio = false;
> > >  }
> > > 
> > > +static void intel_dp_upfront_dpms_off(struct drm_connector *connector,
> > > +				struct drm_modeset_acquire_ctx *ctx)
> > > +{
> > > +	struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > +	struct intel_digital_port *intel_dig_port =
> > > dp_to_dig_port(intel_dp);
> > > +	struct drm_crtc *crtc = intel_dig_port->base.base.crtc;
> > > +	struct intel_load_detect_pipe tmp;
> > > +
> > > +	if (intel_get_load_detect_pipe(connector, NULL, &tmp, ctx)) {
> > > +		crtc->acquire_ctx = ctx;
> > > +		tmp.dpms_mode = DRM_MODE_DPMS_OFF;
> > > +		intel_release_load_detect_pipe(connector, &tmp, ctx);
> > > +	}
> > > +}
> > > +
> > > +static void intel_dp_upfront_dpms_on(struct drm_connector *connector,
> > > +				struct drm_modeset_acquire_ctx *ctx)
> > > +{
> > > +	struct intel_load_detect_pipe tmp;
> > > +
> > > +	intel_get_load_detect_pipe(connector, NULL, &tmp, ctx);
> > > +
> > > +	drm_modeset_drop_locks(ctx);
> > > +	drm_modeset_acquire_fini(ctx);
> > > +}
> > > +
> > > +static bool intel_dp_upfront_link_train(struct drm_connector *connector)
> > > +{
> > > +	struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > +	struct intel_digital_port *intel_dig_port =
> > > dp_to_dig_port(intel_dp);
> > > +	struct intel_encoder *intel_encoder = &intel_dig_port->base;
> > > +	struct drm_device *dev = intel_encoder->base.dev;
> > > +	struct drm_crtc *crtc = intel_dig_port->base.base.crtc;
> > > +	struct intel_crtc *intel_crtc = crtc ? to_intel_crtc(crtc) :
> > > NULL;
> > > +	struct drm_modeset_acquire_ctx ctx, *old_ctx = NULL;
> > > +	bool ret = true, need_dpms_on = false;
> > > +
> > > +	if (!IS_BROXTON(dev))
> > > +		return true;
> > > +	/*
> > > +	 * On hotplug cases, we call _upfront_link_train directly.
> > > +	 * In connected boot scenarios (boot with {MIPI/eDP} + DP),
> > > +	 * BIOS typically brings up DP. Hence, we disable the crtc
> > > +	 * to do _upfront_link_training and then re-enable it back.
> > > +	 */
> > > +	if (crtc && crtc->enabled && intel_crtc->active) {
> > > +		DRM_DEBUG_KMS("Disabling pipe %c\n", pipe_name(intel_crtc
> > > ->pipe));
> > > +		old_ctx = crtc->acquire_ctx;
> > > +		drm_modeset_acquire_init(&ctx, 0);
> > > +		intel_dp_upfront_dpms_off(connector, &ctx);
> > > +		need_dpms_on = true;
> > > +	}
> > > +
> > > +	if (HAS_DDI(dev))
> > > +		ret = intel_ddi_upfront_link_train(intel_dp, intel_crtc);
> > > +		/* Other platforms upfront link train call goes here..*/
> > > +
> > > +	if (need_dpms_on) {
> > > +		intel_dp_upfront_dpms_on(connector, &ctx);
> > > +		crtc->acquire_ctx = old_ctx;
> > > +	}
> > > +	return ret;
> > > +}
> > > +
> > > +
> > >  static enum drm_connector_status
> > >  intel_dp_detect(struct drm_connector *connector, bool force)
> > >  {
> > > @@ -4631,7 +4696,7 @@ intel_dp_detect(struct drm_connector *connector,
> > > bool
> > > force)
> > >  	struct drm_device *dev = connector->dev;
> > >  	enum drm_connector_status status;
> > >  	enum intel_display_power_domain power_domain;
> > > -	bool ret;
> > > +	bool ret, do_upfront_link_train;
> > >  	u8 sink_irq_vector;
> > > 
> > >  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> > > @@ -4705,6 +4770,16 @@ intel_dp_detect(struct drm_connector *connector,
> > > bool
> > > force)
> > >  			DRM_DEBUG_DRIVER("CP or sink specific irq
> > > unhandled\n");
> > >  	}
> > > 
> > > +	/* Do not do upfront link train, if it is a compliance request */
> > > +	do_upfront_link_train =
> > > +		intel_encoder->type == INTEL_OUTPUT_DISPLAYPORT &&
> > > +		intel_dp->compliance_test_type != DP_TEST_LINK_TRAINING;
> > > +
> > > +	if (do_upfront_link_train) {
> > > +		ret = intel_dp_upfront_link_train(connector);
> > > +		if (!ret)
> > > +			status = connector_status_disconnected;
> > > +	}
> > >  out:
> > >  	intel_display_power_put(to_i915(dev), power_domain);
> > >  	return status;
> > > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > > b/drivers/gpu/drm/i915/intel_drv.h
> > > index 5912955..3cfab20 100644
> > > --- a/drivers/gpu/drm/i915/intel_drv.h
> > > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > > @@ -1025,6 +1025,8 @@ void intel_ddi_clock_get(struct intel_encoder
> > > *encoder,
> > >  			 struct intel_crtc_state *pipe_config);
> > >  void intel_ddi_set_vc_payload_alloc(struct drm_crtc *crtc, bool state);
> > >  uint32_t ddi_signal_levels(struct intel_dp *intel_dp);
> > > +bool intel_ddi_upfront_link_train(struct intel_dp *intel_dp,
> > > +				struct intel_crtc *crtc);
> > > 
> > >  /* intel_frontbuffer.c */
> > >  void intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
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