Message-ID: <20160318155720.GG14170@phenom.ffwll.local>
Date:	Fri, 18 Mar 2016 16:57:21 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Jani Nikula <jani.nikula@...ux.intel.com>
Cc:	Lyude <cpaul@...hat.com>, intel-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...el.com>,
	arthur.j.runyan@...el.com, open list <linux-kernel@...r.kernel.org>
Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915: Get rid of
 intel_dp_dpcd_read_wake()

On Thu, Mar 17, 2016 at 07:56:33PM +0200, Jani Nikula wrote:
> On Thu, 17 Mar 2016, Lyude <cpaul@...hat.com> wrote:
> > Since we've fixed up drm_dp_dpcd_read() to allow for retries when things
> > timeout, there's no use for having this function anymore. Good riddens.
> >
> > Signed-off-by: Lyude <cpaul@...hat.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 79 ++++++++++++-----------------------------
> >  1 file changed, 22 insertions(+), 57 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index cdc2c15..fb4cbbe5 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -3190,47 +3190,14 @@ static void chv_dp_post_pll_disable(struct intel_encoder *encoder)
> >  }
> >  
> >  /*
> > - * Native read with retry for link status and receiver capability reads for
> > - * cases where the sink may still be asleep.
> > - *
> > - * Sinks are *supposed* to come up within 1ms from an off state, but we're also
> > - * supposed to retry 3 times per the spec.
> > - */
> > -static ssize_t
> > -intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset,
> > -			void *buffer, size_t size)
> > -{
> > -	ssize_t ret;
> > -	int i;
> > -
> > -	/*
> > -	 * Sometime we just get the same incorrect byte repeated
> > -	 * over the entire buffer. Doing just one throw away read
> > -	 * initially seems to "solve" it.
> > -	 */
> > -	drm_dp_dpcd_read(aux, DP_DPCD_REV, buffer, 1);
> 
> Last time around I dug out the commit adding the line above, which fixed
> a bug, and said it should be accounted for somehow. But I've had a
> change of heart. I want this function gone already. We've improved the
> dp helpers considerably, and if this regresses, we need to look at
> fixing this either at the drm level or in our ->transfer hook.
> 
> Acked-by: Jani Nikula <jani.nikula@...el.com>

Hm, my idea was actually to 1:1 move intel_dp_dpcd_read_wake logic into
drm_dp_dpcd_read, without any functional change for i915.ko. And everyone
else shouldn't complain about a few more retries either.

That would also address Ville's grumpy nack.
-Daniel

> 
> 
> > -
> > -	for (i = 0; i < 3; i++) {
> > -		ret = drm_dp_dpcd_read(aux, offset, buffer, size);
> > -		if (ret == size)
> > -			return ret;
> > -		msleep(1);
> > -	}
> > -
> > -	return ret;
> > -}
> > -
> > -/*
> >   * Fetch AUX CH registers 0x202 - 0x207 which contain
> >   * link status information
> >   */
> >  bool
> >  intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE])
> >  {
> > -	return intel_dp_dpcd_read_wake(&intel_dp->aux,
> > -				       DP_LANE0_1_STATUS,
> > -				       link_status,
> > -				       DP_LINK_STATUS_SIZE) == DP_LINK_STATUS_SIZE;
> > +	return drm_dp_dpcd_read(&intel_dp->aux, DP_LANE0_1_STATUS, link_status,
> > +				DP_LINK_STATUS_SIZE) == DP_LINK_STATUS_SIZE;
> >  }
> >  
> >  /* These are source-specific values. */
> > @@ -3865,8 +3832,8 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  	uint8_t rev;
> >  
> > -	if (intel_dp_dpcd_read_wake(&intel_dp->aux, 0x000, intel_dp->dpcd,
> > -				    sizeof(intel_dp->dpcd)) < 0)
> > +	if (drm_dp_dpcd_read(&intel_dp->aux, 0x000, intel_dp->dpcd,
> > +			     sizeof(intel_dp->dpcd)) < 0)
> >  		return false; /* aux transfer failed */
> >  
> >  	DRM_DEBUG_KMS("DPCD: %*ph\n", (int) sizeof(intel_dp->dpcd), intel_dp->dpcd);
> > @@ -3877,9 +3844,9 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> >  	/* Check if the panel supports PSR */
> >  	memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
> >  	if (is_edp(intel_dp)) {
> > -		intel_dp_dpcd_read_wake(&intel_dp->aux, DP_PSR_SUPPORT,
> > -					intel_dp->psr_dpcd,
> > -					sizeof(intel_dp->psr_dpcd));
> > +		drm_dp_dpcd_read(&intel_dp->aux, DP_PSR_SUPPORT,
> > +				 intel_dp->psr_dpcd,
> > +				 sizeof(intel_dp->psr_dpcd));
> >  		if (intel_dp->psr_dpcd[0] & DP_PSR_IS_SUPPORTED) {
> >  			dev_priv->psr.sink_support = true;
> >  			DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
> > @@ -3890,9 +3857,9 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> >  			uint8_t frame_sync_cap;
> >  
> >  			dev_priv->psr.sink_support = true;
> > -			intel_dp_dpcd_read_wake(&intel_dp->aux,
> > -					DP_SINK_DEVICE_AUX_FRAME_SYNC_CAP,
> > -					&frame_sync_cap, 1);
> > +			drm_dp_dpcd_read(&intel_dp->aux,
> > +					 DP_SINK_DEVICE_AUX_FRAME_SYNC_CAP,
> > +					 &frame_sync_cap, 1);
> >  			dev_priv->psr.aux_frame_sync = frame_sync_cap ? true : false;
> >  			/* PSR2 needs frame sync as well */
> >  			dev_priv->psr.psr2_support = dev_priv->psr.aux_frame_sync;
> > @@ -3908,15 +3875,13 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> >  	/* Intermediate frequency support */
> >  	if (is_edp(intel_dp) &&
> >  	    (intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] &	DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
> > -	    (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_EDP_DPCD_REV, &rev, 1) == 1) &&
> > +	    (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV, &rev, 1) == 1) &&
> >  	    (rev >= 0x03)) { /* eDp v1.4 or higher */
> >  		__le16 sink_rates[DP_MAX_SUPPORTED_RATES];
> >  		int i;
> >  
> > -		intel_dp_dpcd_read_wake(&intel_dp->aux,
> > -				DP_SUPPORTED_LINK_RATES,
> > -				sink_rates,
> > -				sizeof(sink_rates));
> > +		drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES,
> > +				sink_rates, sizeof(sink_rates));
> >  
> >  		for (i = 0; i < ARRAY_SIZE(sink_rates); i++) {
> >  			int val = le16_to_cpu(sink_rates[i]);
> > @@ -3939,9 +3904,9 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> >  	if (intel_dp->dpcd[DP_DPCD_REV] == 0x10)
> >  		return true; /* no per-port downstream info */
> >  
> > -	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_DOWNSTREAM_PORT_0,
> > -				    intel_dp->downstream_ports,
> > -				    DP_MAX_DOWNSTREAM_PORTS) < 0)
> > +	if (drm_dp_dpcd_read(&intel_dp->aux, DP_DOWNSTREAM_PORT_0,
> > +			     intel_dp->downstream_ports,
> > +			     DP_MAX_DOWNSTREAM_PORTS) < 0)
> >  		return false; /* downstream port status fetch failed */
> >  
> >  	return true;
> > @@ -3955,11 +3920,11 @@ intel_dp_probe_oui(struct intel_dp *intel_dp)
> >  	if (!(intel_dp->dpcd[DP_DOWN_STREAM_PORT_COUNT] & DP_OUI_SUPPORT))
> >  		return;
> >  
> > -	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_OUI, buf, 3) == 3)
> > +	if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_OUI, buf, 3) == 3)
> >  		DRM_DEBUG_KMS("Sink OUI: %02hx%02hx%02hx\n",
> >  			      buf[0], buf[1], buf[2]);
> >  
> > -	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_BRANCH_OUI, buf, 3) == 3)
> > +	if (drm_dp_dpcd_read(&intel_dp->aux, DP_BRANCH_OUI, buf, 3) == 3)
> >  		DRM_DEBUG_KMS("Branch OUI: %02hx%02hx%02hx\n",
> >  			      buf[0], buf[1], buf[2]);
> >  }
> > @@ -3975,7 +3940,7 @@ intel_dp_probe_mst(struct intel_dp *intel_dp)
> >  	if (intel_dp->dpcd[DP_DPCD_REV] < 0x12)
> >  		return false;
> >  
> > -	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_MSTM_CAP, buf, 1)) {
> > +	if (drm_dp_dpcd_read(&intel_dp->aux, DP_MSTM_CAP, buf, 1)) {
> >  		if (buf[0] & DP_MST_CAP) {
> >  			DRM_DEBUG_KMS("Sink is MST capable\n");
> >  			intel_dp->is_mst = true;
> > @@ -4112,7 +4077,7 @@ stop:
> >  static bool
> >  intel_dp_get_sink_irq(struct intel_dp *intel_dp, u8 *sink_irq_vector)
> >  {
> > -	return intel_dp_dpcd_read_wake(&intel_dp->aux,
> > +	return drm_dp_dpcd_read(&intel_dp->aux,
> >  				       DP_DEVICE_SERVICE_IRQ_VECTOR,
> >  				       sink_irq_vector, 1) == 1;
> >  }
> > @@ -4122,7 +4087,7 @@ intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *sink_irq_vector)
> >  {
> >  	int ret;
> >  
> > -	ret = intel_dp_dpcd_read_wake(&intel_dp->aux,
> > +	ret = drm_dp_dpcd_read(&intel_dp->aux,
> >  					     DP_SINK_COUNT_ESI,
> >  					     sink_irq_vector, 14);
> >  	if (ret != 14)
> > @@ -4383,7 +4348,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
> >  	    intel_dp->downstream_ports[0] & DP_DS_PORT_HPD) {
> >  		uint8_t reg;
> >  
> > -		if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
> > +		if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_COUNT,
> >  					    &reg, 1) < 0)
> >  			return connector_status_unknown;
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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

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