Re: [RFC 11/13] drm/dp: Add helper to dump DPCD

[Rafael Antognolli <rafael.antognolli@intel.com>]

On Fri, Aug 14, 2015 at 02:56:55PM +0300, Jani Nikula wrote:
> On Wed, 12 Aug 2015, Thierry Reding <thierry.reding@gmail.com> wrote:
> > From: Thierry Reding <treding@nvidia.com>
> >
> > The new drm_dp_dpcd_dump() helper dumps the contents of a DPCD to a
> > seq_file and can be used to make the DPCD available via debugfs for
> > example.
> 
> See i915/i915_debugfs.c for one DPCD dump implementation.
> 
> Around the time that was added, there was also some discussion (and
> patches [1]) to expose a read/write debugfs interface to DPCD, letting
> userspace access arbitrary DPCD registers.
> 
> Just this week there was some discussion about revisiting that. It was
> about accessing some proprietary panel features, but there's also the
> ease of debugging without having to keep updating the kernel to dump
> more.
> 
> I think it would be great to agree on a common debugfs interface to
> access DPCD arbitrarily. Last time I checked, the blocker to that was
> access to the aux channel from generic code; it's always driver
> specific. SMOP. ;)

Do you mean it would require the generic code/interface to somehow route
this to the driver specific code? I am not sure yet how this works (if
there's something like it around), but I'll take a look.

> I could put some effort into this (maybe Rafael too?), as long as we
> could agree on the interface. As I wrote in the referenced thread, I
> wasn't thrilled about what was proposed.
> 

Yes, I'm willing to put effort into this, for sure. Any help pointing to
which direction to follow is greatly appreciated.

Thanks,
Rafael

> 
> 
> [1] http://mid.gmane.org/1428493301-20293-1-git-send-email-durgadoss.r@intel.com
> 
> 
> 
> >
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> >  drivers/gpu/drm/drm_dp_helper.c | 146 ++++++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_dp_helper.h     |   2 +
> >  2 files changed, 148 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> > index 8968201ea93c..ea74884c9cb3 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -27,6 +27,7 @@
> >  #include <linux/errno.h>
> >  #include <linux/sched.h>
> >  #include <linux/i2c.h>
> > +#include <linux/seq_file.h>
> >  #include <drm/drm_dp_helper.h>
> >  #include <drm/drmP.h>
> >  
> > @@ -292,6 +293,151 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
> >  }
> >  EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
> >  
> > +/**
> > + * drm_dp_dpcd_dump() - dump DPCD content
> > + * @aux: DisplayPort AUX channel
> > + * @s: destination for DPCD dump
> > + *
> > + * Reads registers from the DPCD via a DisplayPort AUX channel and dumps them
> > + * to a seq_file.
> > + */
> > +void drm_dp_dpcd_dump(struct drm_dp_aux *aux, struct seq_file *s)
> > +{
> > +#define DUMP_REG(aux, offset) ({					\
> > +		u8 value;						\
> > +		int err;						\
> > +		err = drm_dp_dpcd_readb(aux, offset, &value);		\
> > +		if (err < 0) {						\
> > +			dev_err((aux)->dev, "failed to read %s: %d\n",	\
> > +				#offset, err);				\
> > +			return;						\
> > +		}							\
> > +		seq_printf(s, "%-35s 0x%04x 0x%02x\n", #offset, offset,	\
> > +			   value);					\
> > +	})
> > +
> > +	DUMP_REG(aux, DP_DPCD_REV);
> > +	DUMP_REG(aux, DP_MAX_LINK_RATE);
> > +	DUMP_REG(aux, DP_MAX_LANE_COUNT);
> > +	DUMP_REG(aux, DP_MAX_DOWNSPREAD);
> > +	DUMP_REG(aux, DP_NORP);
> > +	DUMP_REG(aux, DP_DOWNSTREAMPORT_PRESENT);
> > +	DUMP_REG(aux, DP_MAIN_LINK_CHANNEL_CODING);
> > +	DUMP_REG(aux, DP_DOWN_STREAM_PORT_COUNT);
> > +	DUMP_REG(aux, DP_RECEIVE_PORT_0_CAP_0);
> > +	DUMP_REG(aux, DP_RECEIVE_PORT_0_BUFFER_SIZE);
> > +	DUMP_REG(aux, DP_RECEIVE_PORT_1_CAP_0);
> > +	DUMP_REG(aux, DP_RECEIVE_PORT_1_BUFFER_SIZE);
> > +	DUMP_REG(aux, DP_I2C_SPEED_CAP);
> > +	DUMP_REG(aux, DP_EDP_CONFIGURATION_CAP);
> > +	DUMP_REG(aux, DP_TRAINING_AUX_RD_INTERVAL);
> > +	DUMP_REG(aux, DP_ADAPTER_CAP);
> > +	DUMP_REG(aux, DP_SUPPORTED_LINK_RATES);
> > +	DUMP_REG(aux, DP_FAUX_CAP);
> > +	DUMP_REG(aux, DP_MSTM_CAP);
> > +	DUMP_REG(aux, DP_NUMBER_OF_AUDIO_ENDPOINTS);
> > +	DUMP_REG(aux, DP_AV_GRANULARITY);
> > +	DUMP_REG(aux, DP_AUD_DEC_LAT0);
> > +	DUMP_REG(aux, DP_AUD_DEC_LAT1);
> > +	DUMP_REG(aux, DP_AUD_PP_LAT0);
> > +	DUMP_REG(aux, DP_AUD_PP_LAT1);
> > +	DUMP_REG(aux, DP_VID_INTER_LAT);
> > +	DUMP_REG(aux, DP_VID_PROG_LAT);
> > +	DUMP_REG(aux, DP_REP_LAT);
> > +	DUMP_REG(aux, DP_AUD_DEL_INS0);
> > +	DUMP_REG(aux, DP_AUD_DEL_INS1);
> > +	DUMP_REG(aux, DP_AUD_DEL_INS2);
> > +	DUMP_REG(aux, DP_RECEIVER_ALPM_CAP);
> > +	DUMP_REG(aux, DP_AUD_DEL_INS0);
> > +	DUMP_REG(aux, DP_GUID);
> > +	DUMP_REG(aux, DP_PSR_SUPPORT);
> > +	DUMP_REG(aux, DP_PSR_CAPS);
> > +	DUMP_REG(aux, DP_DOWNSTREAM_PORT_0);
> > +	DUMP_REG(aux, DP_LINK_BW_SET);
> > +	DUMP_REG(aux, DP_LANE_COUNT_SET);
> > +	DUMP_REG(aux, DP_TRAINING_PATTERN_SET);
> > +	DUMP_REG(aux, DP_TRAINING_LANE0_SET);
> > +	DUMP_REG(aux, DP_TRAINING_LANE1_SET);
> > +	DUMP_REG(aux, DP_TRAINING_LANE2_SET);
> > +	DUMP_REG(aux, DP_TRAINING_LANE3_SET);
> > +	DUMP_REG(aux, DP_DOWNSPREAD_CTRL);
> > +	DUMP_REG(aux, DP_MAIN_LINK_CHANNEL_CODING_SET);
> > +	DUMP_REG(aux, DP_I2C_SPEED_CONTROL_STATUS);
> > +	DUMP_REG(aux, DP_EDP_CONFIGURATION_SET);
> > +	DUMP_REG(aux, DP_LINK_QUAL_LANE0_SET);
> > +	DUMP_REG(aux, DP_LINK_QUAL_LANE1_SET);
> > +	DUMP_REG(aux, DP_LINK_QUAL_LANE2_SET);
> > +	DUMP_REG(aux, DP_LINK_QUAL_LANE3_SET);
> > +	DUMP_REG(aux, DP_TRAINING_LANE0_1_SET2);
> > +	DUMP_REG(aux, DP_TRAINING_LANE2_3_SET2);
> > +	DUMP_REG(aux, DP_MSTM_CTRL);
> > +	DUMP_REG(aux, DP_AUDIO_DELAY0);
> > +	DUMP_REG(aux, DP_AUDIO_DELAY1);
> > +	DUMP_REG(aux, DP_AUDIO_DELAY2);
> > +	DUMP_REG(aux, DP_LINK_RATE_SET);
> > +	DUMP_REG(aux, DP_RECEIVER_ALPM_CONFIG);
> > +	DUMP_REG(aux, DP_SINK_DEVICE_AUX_FRAME_SYNC_CONF);
> > +	DUMP_REG(aux, DP_UPSTREAM_DEVICE_DP_PWR_NEED);
> > +	DUMP_REG(aux, DP_AUX_FRAME_SYNC_VALUE);
> > +	DUMP_REG(aux, DP_PSR_EN_CFG);
> > +	DUMP_REG(aux, DP_ADAPTER_CTRL);
> > +	DUMP_REG(aux, DP_BRANCH_DEVICE_CTRL);
> > +	DUMP_REG(aux, DP_PAYLOAD_ALLOCATE_SET);
> > +	DUMP_REG(aux, DP_PAYLOAD_ALLOCATE_START_TIME_SLOT);
> > +	DUMP_REG(aux, DP_PAYLOAD_ALLOCATE_TIME_SLOT_COUNT);
> > +	DUMP_REG(aux, DP_SINK_COUNT);
> > +	DUMP_REG(aux, DP_DEVICE_SERVICE_IRQ_VECTOR);
> > +	DUMP_REG(aux, DP_LANE0_1_STATUS);
> > +	DUMP_REG(aux, DP_LANE2_3_STATUS);
> > +	DUMP_REG(aux, DP_LANE_ALIGN_STATUS_UPDATED);
> > +	DUMP_REG(aux, DP_SINK_STATUS);
> > +	DUMP_REG(aux, DP_ADJUST_REQUEST_LANE0_1);
> > +	DUMP_REG(aux, DP_ADJUST_REQUEST_LANE2_3);
> > +	DUMP_REG(aux, DP_TEST_REQUEST);
> > +	DUMP_REG(aux, DP_TEST_LINK_RATE);
> > +	DUMP_REG(aux, DP_TEST_LANE_COUNT);
> > +	DUMP_REG(aux, DP_TEST_CRC_R_CR);
> > +	DUMP_REG(aux, DP_TEST_CRC_G_Y);
> > +	DUMP_REG(aux, DP_TEST_CRC_B_CB);
> > +	DUMP_REG(aux, DP_TEST_SINK_MISC);
> > +	DUMP_REG(aux, DP_TEST_RESPONSE);
> > +	DUMP_REG(aux, DP_TEST_EDID_CHECKSUM);
> > +	DUMP_REG(aux, DP_TEST_SINK);
> > +	DUMP_REG(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS);
> > +	DUMP_REG(aux, DP_VC_PAYLOAD_ID_SLOT_1);
> > +	DUMP_REG(aux, DP_SOURCE_OUI);
> > +	DUMP_REG(aux, DP_SINK_OUI);
> > +	DUMP_REG(aux, DP_BRANCH_OUI);
> > +	DUMP_REG(aux, DP_SET_POWER);
> > +	DUMP_REG(aux, DP_EDP_DPCD_REV);
> > +	DUMP_REG(aux, DP_EDP_GENERAL_CAP_1);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_ADJUSTMENT_CAP);
> > +	DUMP_REG(aux, DP_EDP_GENERAL_CAP_2);
> > +	DUMP_REG(aux, DP_EDP_GENERAL_CAP_3);
> > +	DUMP_REG(aux, DP_EDP_DISPLAY_CONTROL_REGISTER);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_LSB);
> > +	DUMP_REG(aux, DP_EDP_PWMGEN_BIT_COUNT);
> > +	DUMP_REG(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN);
> > +	DUMP_REG(aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_CONTROL_STATUS);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_SET);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_CAP_MIN_MSB);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_CAP_MIN_MID);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_CAP_MIN_LSB);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_CAP_MAX_MSB);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_CAP_MAX_MID);
> > +	DUMP_REG(aux, DP_EDP_BACKLIGHT_FREQ_CAP_MAX_LSB);
> > +	DUMP_REG(aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET);
> > +	DUMP_REG(aux, DP_EDP_DBC_MAXIMUM_BRIGHTNESS_SET);
> > +	DUMP_REG(aux, DP_EDP_REGIONAL_BACKLIGHT_BASE);
> > +	DUMP_REG(aux, DP_EDP_REGIONAL_BACKLIGHT_0);
> > +
> > +#undef DUMP_REG
> > +}
> > +EXPORT_SYMBOL(drm_dp_dpcd_dump);
> > +
> >  static void drm_dp_link_reset(struct drm_dp_link *link)
> >  {
> >  	if (!link)
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index d041bb00d6a0..089d274f857d 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -754,6 +754,8 @@ static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
> >  int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
> >  				 u8 status[DP_LINK_STATUS_SIZE]);
> >  
> > +void drm_dp_dpcd_dump(struct drm_dp_aux *aux, struct seq_file *s);
> > +
> >  /**
> >   * struct drm_dp_link_train_set - link training settings
> >   * @voltage_swing: per-lane voltage swing
> > -- 
> > 2.4.5
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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