[Intel-gfx] [PATCH v4 1/1] drm/i915/skl+: Add and enable DP AUX CH mutex

[Pandiyan, Dhinakaran]

On Mon, 2018-02-26 at 14:41 -0800, Rodrigo Vivi wrote:
> On Mon, Feb 26, 2018 at 01:48:37PM -0800, José Roberto de Souza wrote:
> > When PSR/PSR2/GTC is enabled hardware can do AUX transactions by it
> > self, so lets use the mutex register that is available in gen9+ to
> > avoid concurrent access by hardware and driver.
> > Older gen handling will be done separated.
> > 
> > Reference: https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-skl-vol12-display.pdf
> > Page 198 - AUX programming sequence
> > 
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Cc: Jani Nikula <jani.nikula at linux.intel.com>
> > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h |  9 ++++++++
> >  drivers/gpu/drm/i915/intel_dp.c | 47 +++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 56 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index eea5b2c537d4..f36e839b4b4f 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -5385,6 +5385,15 @@ enum {
> >  #define   DP_AUX_CH_CTL_FW_SYNC_PULSE_SKL(c) (((c) - 1) << 5)
> >  #define   DP_AUX_CH_CTL_SYNC_PULSE_SKL(c)   ((c) - 1)
> >  
> > +#define _DPA_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6402C)
> > +#define _DPB_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6412C)
> > +#define _DPC_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6422C)
> > +#define _DPD_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6432C)
> > +#define _DPF_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6452C)
> > +#define DP_AUX_CH_MUTEX(port)	_MMIO_PORT(port, _DPA_AUX_CH_MUTEX, _DPB_AUX_CH_MUTEX)
> 
> s/port/aux_ch
> 
> > +#define   DP_AUX_CH_MUTEX_ENABLE		(1 << 31)
> > +#define   DP_AUX_CH_MUTEX_STATUS		(1 << 30)
> > +
> >  /*
> >   * Computing GMCH M and N values for the Display Port link
> >   *
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 2c3eb90b9499..7004239e4c9e 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1081,6 +1081,42 @@ static uint32_t intel_dp_get_aux_send_ctl(struct intel_dp *intel_dp,
> >  						aux_clock_divider);
> >  }
> >  
> > +static bool intel_dp_aux_ch_trylock(struct intel_dp *intel_dp)
> > +{
> > +	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> > +	struct drm_i915_private *dev_priv =
> > +			to_i915(intel_dig_port->base.base.dev);
> > +
> > +	if (INTEL_GEN(dev_priv) < 9)
> > +		return true;
> > +
> > +	/* Spec says that mutex is acquired when status bit is read as unset,
> > +	 * here waiting for 2msec(+-4 aux transactions) before give up.
> > +	 */
> > +	if (intel_wait_for_register(dev_priv, DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> > +				    DP_AUX_CH_MUTEX_STATUS, 0, 2)) {
> > +		DRM_DEBUG_KMS("aux channel %c locked for 2msec, timing out\n",
> > +			      aux_ch_name(intel_dp->aux_ch));
> > +		return false;
> > +	}
> > +

With nits that Rodrigo pointed out addressed, feel free to use

Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>

Btw for future reference, including change log in the commit message is
a good idea in the absence of a cover letter.


> > +	return true;
> > +}
> > +
> > +static void intel_dp_aux_ch_unlock(struct intel_dp *intel_dp)
> > +{
> > +	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> > +	struct drm_i915_private *dev_priv =
> > +			to_i915(intel_dig_port->base.base.dev);
> > +
> > +	if (INTEL_GEN(dev_priv) < 9)
> > +		return;
> > +
> > +	/* set the status bit releases the mutex + keeping mutex enabled */
> > +	I915_WRITE(DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> > +		   DP_AUX_CH_MUTEX_ENABLE | DP_AUX_CH_MUTEX_STATUS);
> > +}
> > +
> >  static int
> >  intel_dp_aux_ch(struct intel_dp *intel_dp,
> >  		const uint8_t *send, int send_bytes,
> > @@ -1119,6 +1155,11 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
> >  
> >  	intel_dp_check_edp(intel_dp);
> >  
> > +	if (!intel_dp_aux_ch_trylock(intel_dp)) {
> > +		ret = -EBUSY;
> > +		goto out_locked;
> 
> out_"locked" confused me here...
> 
> not sure about a better name...
> 
> maybe out_aux_unlocked ?! :/
> 
> > +	}
> > +
> >  	/* Try to wait for any previous AUX channel activity */
> >  	for (try = 0; try < 3; try++) {
> >  		status = I915_READ_NOTRACE(ch_ctl);
> > @@ -1248,6 +1289,8 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
> >  
> >  	ret = recv_bytes;
> >  out:
> > +	intel_dp_aux_ch_unlock(intel_dp);
> > +out_locked:
> >  	pm_qos_update_request(&dev_priv->pm_qos, PM_QOS_DEFAULT_VALUE);
> >  
> >  	if (vdd)
> > @@ -1544,6 +1587,10 @@ intel_dp_aux_init(struct intel_dp *intel_dp)
> >  	else
> >  		intel_dp->get_aux_send_ctl = g4x_get_aux_send_ctl;
> >  
> > +	if (INTEL_GEN(dev_priv) >= 9)
> > +		I915_WRITE(DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> > +			   DP_AUX_CH_MUTEX_ENABLE);
> > +
> 
> Cool! I believe we are in a good shape now...
> 
> with s/port/aux_ch corrected and preferably with a better goto out name:
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> 
> >  	drm_dp_aux_init(&intel_dp->aux);
> >  
> >  	/* Failure to allocate our preferred name is not critical */
> > -- 
> > 2.16.2
> >