On Fri, Mar 02, 2018 at 11:20:42PM +0000, Pandiyan, Dhinakaran wrote:
> 
> 
> 
> On Thu, 2018-03-01 at 12:53 +0200, Ville Syrjälä wrote:
> > On Wed, Feb 28, 2018 at 11:55:39PM +0000, Souza, Jose wrote:
> > > On Wed, 2018-02-28 at 13:09 +0200, Ville Syrjälä wrote:
> > > > On Wed, Feb 28, 2018 at 12:57:07AM +0000, Souza, Jose wrote:
> > > > > On Tue, 2018-02-27 at 23:34 +0200, Ville Syrjälä wrote:
> > > > > > On Tue, Feb 27, 2018 at 01:23:59PM -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/int
> > > > > > > el-g
> > > > > > > fx-prm-osrc-skl-vol12-display.pdf
> > > > > > > Page 198 - AUX programming sequence
> > > > > > > 
> > > > > > > Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandi...@intel.com
> > > > > > > >
> > > > > > > Reviewed-by: Rodrigo Vivi <rodrigo.v...@intel.com>
> > > > > > > Cc: Jani Nikula <jani.nik...@linux.intel.com>
> > > > > > > Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> > > > > > > Signed-off-by: José Roberto de Souza <jose.so...@intel.com>
> > > > > > > ---
> > > > > > > 
> > > > > > > Changelog:
> > > > > > > v2
> > > > > > > - removed the PSR dependency, now getting lock all the times
> > > > > > > when
> > > > > > > available
> > > > > > > - renamed functions to avoid nested calls
> > > > > > > - moved register bits right after the DP_AUX_CH_MUTEX()
> > > > > > > - removed 'drm/i915: keep AUX powered while PSR is enabled'
> > > > > > > Dhinakaran Pandiyan will sent a better and final version
> > > > > > > v3
> > > > > > > - rebased on top of Ville's AUX series
> > > > > > > - moved port registers to above DP_AUX_CH_MUTEX()
> > > > > > > - using intel_wait_for_register() instead of the internal
> > > > > > > version
> > > > > > > v4
> > > > > > > - removed virtual function to get mutex register address
> > > > > > > - enabling the mutex back only on aux channel init
> > > > > > > - added the aux channel name to the timeout debug message
> > > > > > > v5
> > > > > > > - renamed DP_AUX_CH_MUTEX() parameter to aux_ch
> > > > > > > - renamed goto label when intel_dp_aux_ch_trylock() fails
> > > > > > > 
> > > > > > >  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..bce2e6dad4c4 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(aux_ch)  _MMIO_PORT(aux_ch,
> > > > > > > _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 2a3b3ae4e3da..7f4bf77227cd 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_divi
> > > > > > > der)
> > > > > > > ;
> > > > > > >  }
> > > > > > >  
> > > > > > > +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;
> > > > > > > + }
> > > > > > > +
> > > > > > > + 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_aux_ch_unlocked;
> > > > > > > + }
> > > > > > > +
> > > > > > >   /* Try to wait for any previous AUX channel activity
> > > > > > > */
> > > > > > >   for (try = 0; try < 3; try++) {
> > > > > > >           status = I915_READ_NOTRACE(ch_ctl);
> > > > > > > @@ -1240,6 +1281,8 @@ intel_dp_aux_ch(struct intel_dp
> > > > > > > *intel_dp,
> > > > > > >  
> > > > > > >   ret = recv_bytes;
> > > > > > >  out:
> > > > > > > + intel_dp_aux_ch_unlock(intel_dp);
> > > > > > > +out_aux_ch_unlocked:
> > > > > > >   pm_qos_update_request(&dev_priv->pm_qos,
> > > > > > > PM_QOS_DEFAULT_VALUE);
> > > > > > >  
> > > > > > >   if (vdd)
> > > > > > > @@ -1536,6 +1579,10 @@ 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);
> > > > > > 
> > > > > > And who enables it after system/runtime PM etc.? Not sure how
> > > > > > much
> > > > > > sense
> > > > > > there is to finesse this anyway. One extra mmio write every time
> > > > > > we
> > > > > > try
> > > > > > to acquire the mutex shouldn't kill anyone.
> > > > > 
> > > > > Valid point, but I guess is better enable the mutex in
> > > > > intel_dp_encoder_reset():
> > > > > 
> > > > > "
> > > > > @@ -5293,6 +5340,10 @@ void intel_dp_encoder_reset(struct
> > > > > drm_encoder
> > > > > *encoder)
> > > > > 
> > > > >         pps_lock(intel_dp);
> > > > > 
> > > > > +       if (INTEL_GEN(dev_priv) >= 9)
> > > > > +               I915_WRITE(DP_AUX_CH_MUTEX(intel_dp->aux_ch),
> > > > > +                          DP_AUX_CH_MUTEX_ENABLE);
> > > > > +
> > > > >         if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
> > > > >                 intel_dp->active_pipe = vlv_active_pipe(intel_dp);
> > > > > "
> > > > > 
> > > > > any objections?
> > > > 
> > > > I guess we can hope that dmc takes care of it for dc5/6. But what
> > > > about dc9?
> > > 
> > > Yep, for DC5 and DC6 the registers are restored by hardware but it is
> > > not the case for DC9. If I'm not missing something looks like there is
> > > no handling to restore registers when exiting DC9.
> > 
> > The design of the driver is "program all required registers when you
> > need them" instead of the "blindly save/restore everything" DMC firmware
> > approach.
> > 
> 
> 
> +static bool intel_dp_aux_trylock(struct intel_dp *intel_dp)
> +{
> +       bool enabled;
> +       u32 mutex;
> +
> +       /* READ will try to lock the aux channel if the mutex was
> already
> +        * enabled.
> +        */
> +       mutex = I915_READ(DP_AUX_CH_MUTEX);
> +       enabled = mutex & DP_AUX_CH_MUTEX_ENABLE;
> +
> +       if (!enabled) {
> +               /* mutex is currently disabled, enable it without
> altering the
> +                * status bit in case the HW is using the bit */
> +               I915_WRITE(DP_AUX_CH_MUTEX(intel_dig_port->dp.aux_ch),
> +                          mutex | DP_AUX_CH_MUTEX_ENABLE);
> +
> +               /* Now that the mutex is enabled, request to lock it */
> +               mutex = I915_READ(DP_AUX_CH_MUTEX);
> +       }
> +
> +       if (mutex & DP_AUX_CH_MUTEX_STATUS == 0)
> +               return true;
> +
> +       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;
> +       }
> +
> +       return true;
> +}
> +
> 
> 
> Have I missed anything here?

ops, I wrote before seeing this here.

I like this approach a lot, although I don't believe it is harmful to just 
always set enabled bit.

anyways, +1 for this and probably only setting here.

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