Re: [PATCH v2 1/1] drm/i915: Add and enable DP AUX CH mutex

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Feb 22, 2018 at 08:59:49PM +0200, Ville Syrjälä wrote:
> On Tue, Feb 20, 2018 at 06:23:47PM -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.
> > 
> > Reference: https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-skl-vol12-display.pdf
> > Page 198 - AUX programming sequence
> 
> BTW since HSW/BDW don't have the mutex we should really be disabling PSR
> around aux ch usage on those platforms. Not sure how big of a locking
> inversion exercise it would be to make that happen though.

True. But I believe that can be handled differently.
Probably with Aux power domains blocking PSR off "domain".
Something similar to DC off.

I actually had patches for that lost somewhere... :(

> 
> > 
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h  |  9 ++++++++
> >  drivers/gpu/drm/i915/intel_dp.c  | 50 ++++++++++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/intel_drv.h |  1 +
> >  3 files changed, 60 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 1412abcb27d4..a62e3c1badab 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -5318,6 +5318,7 @@ enum {
> >  #define _DPA_AUX_CH_DATA3	(dev_priv->info.display_mmio_offset + 0x6401c)
> >  #define _DPA_AUX_CH_DATA4	(dev_priv->info.display_mmio_offset + 0x64020)
> >  #define _DPA_AUX_CH_DATA5	(dev_priv->info.display_mmio_offset + 0x64024)
> > +#define _DPA_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6402C)
> >  
> >  #define _DPB_AUX_CH_CTL		(dev_priv->info.display_mmio_offset + 0x64110)
> >  #define _DPB_AUX_CH_DATA1	(dev_priv->info.display_mmio_offset + 0x64114)
> > @@ -5325,6 +5326,7 @@ enum {
> >  #define _DPB_AUX_CH_DATA3	(dev_priv->info.display_mmio_offset + 0x6411c)
> >  #define _DPB_AUX_CH_DATA4	(dev_priv->info.display_mmio_offset + 0x64120)
> >  #define _DPB_AUX_CH_DATA5	(dev_priv->info.display_mmio_offset + 0x64124)
> > +#define _DPB_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6412C)
> >  
> >  #define _DPC_AUX_CH_CTL		(dev_priv->info.display_mmio_offset + 0x64210)
> >  #define _DPC_AUX_CH_DATA1	(dev_priv->info.display_mmio_offset + 0x64214)
> > @@ -5332,6 +5334,7 @@ enum {
> >  #define _DPC_AUX_CH_DATA3	(dev_priv->info.display_mmio_offset + 0x6421c)
> >  #define _DPC_AUX_CH_DATA4	(dev_priv->info.display_mmio_offset + 0x64220)
> >  #define _DPC_AUX_CH_DATA5	(dev_priv->info.display_mmio_offset + 0x64224)
> > +#define _DPC_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6422C)
> >  
> >  #define _DPD_AUX_CH_CTL		(dev_priv->info.display_mmio_offset + 0x64310)
> >  #define _DPD_AUX_CH_DATA1	(dev_priv->info.display_mmio_offset + 0x64314)
> > @@ -5339,6 +5342,7 @@ enum {
> >  #define _DPD_AUX_CH_DATA3	(dev_priv->info.display_mmio_offset + 0x6431c)
> >  #define _DPD_AUX_CH_DATA4	(dev_priv->info.display_mmio_offset + 0x64320)
> >  #define _DPD_AUX_CH_DATA5	(dev_priv->info.display_mmio_offset + 0x64324)
> > +#define _DPD_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6432C)
> >  
> >  #define _DPF_AUX_CH_CTL		(dev_priv->info.display_mmio_offset + 0x64510)
> >  #define _DPF_AUX_CH_DATA1	(dev_priv->info.display_mmio_offset + 0x64514)
> > @@ -5346,6 +5350,7 @@ enum {
> >  #define _DPF_AUX_CH_DATA3	(dev_priv->info.display_mmio_offset + 0x6451c)
> >  #define _DPF_AUX_CH_DATA4	(dev_priv->info.display_mmio_offset + 0x64520)
> >  #define _DPF_AUX_CH_DATA5	(dev_priv->info.display_mmio_offset + 0x64524)
> > +#define _DPF_AUX_CH_MUTEX	(dev_priv->info.display_mmio_offset + 0x6452C)
> >  
> >  #define DP_AUX_CH_CTL(port)	_MMIO_PORT(port, _DPA_AUX_CH_CTL, _DPB_AUX_CH_CTL)
> >  #define DP_AUX_CH_DATA(port, i)	_MMIO(_PORT(port, _DPA_AUX_CH_DATA1, _DPB_AUX_CH_DATA1) + (i) * 4) /* 5 registers */
> > @@ -5378,6 +5383,10 @@ 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 DP_AUX_CH_MUTEX(port)	_MMIO_PORT(port, _DPA_AUX_CH_MUTEX, _DPB_AUX_CH_MUTEX)
> > +#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 f20b25f98e5a..af07563bafba 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1081,6 +1081,45 @@ 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;
> > +
> > +	I915_WRITE(intel_dp->aux_ch_mutex_reg, DP_AUX_CH_MUTEX_ENABLE);
> > +
> > +	/* Spec says that mutex is acquired when status bit is read as unset,
> > +	 * if set it should be read again after 500usec. Here waiting for
> > +	 * 2msec or 4 tries before give up.
> > +	 */
> > +	if (__intel_wait_for_register(dev_priv, intel_dp->aux_ch_mutex_reg,
> > +				      DP_AUX_CH_MUTEX_STATUS, 0, 500, 2,
> > +				      NULL)) {
> > +		DRM_WARN("dp_aux_ch port locked for too long");
> > +		return false;
> > +	}
> > +
> > +	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;
> > +
> > +	/* setting the status bit releases the mutex + keep mutex enabled */
> > +	I915_WRITE(intel_dp->aux_ch_mutex_reg, 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,
> > @@ -1115,6 +1154,11 @@ 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;
> > +	}
> > +
> >  	/* Try to wait for any previous AUX channel activity */
> >  	for (try = 0; try < 3; try++) {
> >  		status = I915_READ_NOTRACE(ch_ctl);
> > @@ -1244,6 +1288,8 @@ 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)
> > @@ -1496,6 +1542,10 @@ static void intel_aux_reg_init(struct intel_dp *intel_dp)
> >  	intel_dp->aux_ch_ctl_reg = intel_aux_ctl_reg(dev_priv, port);
> >  	for (i = 0; i < ARRAY_SIZE(intel_dp->aux_ch_data_reg); i++)
> >  		intel_dp->aux_ch_data_reg[i] = intel_aux_data_reg(dev_priv, port, i);
> > +	if (INTEL_INFO(dev_priv)->gen >= 9) {
> > +		intel_dp->aux_ch_mutex_reg = DP_AUX_CH_MUTEX(port);
> > +		I915_WRITE(intel_dp->aux_ch_mutex_reg, DP_AUX_CH_MUTEX_ENABLE);
> > +	}
> >  }
> >  
> >  static void
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index 50874f4035cf..0c88657d6066 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1043,6 +1043,7 @@ struct intel_dp {
> >  	i915_reg_t output_reg;
> >  	i915_reg_t aux_ch_ctl_reg;
> >  	i915_reg_t aux_ch_data_reg[5];
> > +	i915_reg_t aux_ch_mutex_reg;
> >  	uint32_t DP;
> >  	int link_rate;
> >  	uint8_t lane_count;
> > -- 
> > 2.16.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel OTC
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