On Tue, Sep 18, 2018 at 02:19:17PM -0700, Manasi Navare wrote:
> Thanks for the patch. I have tested this on DP 1.4 sink device
> and it works properly to read the DPCDs from different offset and
> use the true capabilities. Without this patch, the sink behaves as a
> legacy DP 1.2 sink.
>
> So with that:
> Tested-by: Manasi Navare <manasi.d.navare at intel.com>
> Acked-by: Manasi Navare <manasi.d.navare at intel.com>
thanks
also:
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
>
> Manasi
>
> On Thu, Sep 13, 2018 at 02:17:20PM -0700, matthew.s.atwood at intel.com wrote:
> > From: Matt Atwood <matthew.s.atwood at intel.com>
> >
> > According to DP spec (2.9.3.1 of DP 1.4) if
> > EXTENDED_RECEIVER_CAPABILITY_FIELD_PRESENT is set the addresses in DPCD
> > 02200h through 0220Fh shall contain the DPRX's true capability. These
> > values will match 00000h through 0000Fh, except for DPCD_REV,
> > MAX_LINK_RATE, DOWN_STREAM_PORT_PRESENT.
> >
> > Read from DPCD once for all 3 values as this is an expensive operation.
> > Spec mentions that all of address space 02200h through 0220Fh should
> > contain the right information however currently only 3 values can
> > differ.
> >
> > There is no address space in the intel_dp->dpcd struct for addresses
> > 02200h through 0220Fh, and since so much of the data is a identical,
> > simply overwrite the values stored in 00000h through 0000Fh with the
> > values that can be overwritten from addresses 02200h through 0220Fh.
> >
> > This patch helps with backward compatibility for devices pre DP1.3.
> >
> > v2: read only dpcd values which can be affected, remove incorrect check,
> > split into drm include changes into separate patch, commit message,
> > verbose debugging statements during overwrite.
> > v3: white space fixes
> > v4: make path dependent on DPCD revision > 1.2
> > v5: split into function, removed DPCD rev check
> > v6: add debugging prints for early exit conditions
> >
> > Signed-off-by: Matt Atwood <matthew.s.atwood at intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 58 +++++++++++++++++++++++++++++++++
> > 1 file changed, 58 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index dde92e4af5d3..1190635e4135 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -3731,6 +3731,62 @@ intel_dp_link_down(struct intel_encoder *encoder,
> > }
> > }
> >
> > +static void
> > +intel_dp_extended_receiver_capabilities(struct intel_dp *intel_dp)
> > +{
> > + /*
> > + * Prior to DP1.3 the bit represented by
> > + * DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT was reserved.
> > + * if it is set DP_DPCD_REV at 0000h could be at a value less than
> > + * the true capability of the panel. The only way to check is to
> > + * then compare 0000h and 2200h.
> > + */
> > + if (intel_dp->dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
> > + DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT) {
> > + uint8_t dpcd_ext[6];
> > +
> > + DRM_DEBUG_KMS("DPCD: Extended Receiver Capability Field Present, accessing 02200h through 022FFh\n");
> > +
> > + if (drm_dp_dpcd_read(&intel_dp->aux, DP_DP13_DPCD_REV,
> > + &dpcd_ext, sizeof(dpcd_ext)) < 0) {
> > + DRM_ERROR("DPCD failed read at extended capabilities\n");
> > + return;
> > + }
> > +
> > + if (intel_dp->dpcd[DP_DPCD_REV] > dpcd_ext[DP_DPCD_REV]) {
> > + DRM_DEBUG_KMS("DPCD extended DPCD rev less than base DPCD rev\n");
> > + return;
> > + }
> > +
> > + if (memcmp(&intel_dp->dpcd[DP_DPCD_REV], &dpcd_ext[DP_DPCD_REV],
> > + sizeof(u8))) {
> > + DRM_DEBUG_KMS("DPCD: new value for DPCD Revision previous value %2x new value %2x\n",
> > + intel_dp->dpcd[DP_DPCD_REV],
> > + dpcd_ext[DP_DPCD_REV]);
> > + memcpy(&intel_dp->dpcd[DP_DPCD_REV],
> > + &dpcd_ext[DP_DPCD_REV], sizeof(u8));
> > + }
> > + if (memcmp(&intel_dp->dpcd[DP_MAX_LINK_RATE],
> > + &dpcd_ext[DP_MAX_LINK_RATE], sizeof(u8))) {
> > + DRM_DEBUG_KMS("DPCD: new value for DPCD Max Link Rate previous value %2x new value %2x\n",
> > + intel_dp->dpcd[DP_MAX_LINK_RATE],
> > + dpcd_ext[DP_MAX_LINK_RATE]);
> > + memcpy(&intel_dp->dpcd[DP_MAX_LINK_RATE],
> > + &dpcd_ext[DP_MAX_LINK_RATE], sizeof(u8));
> > + }
> > + if (memcmp(&intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT],
> > + &dpcd_ext[DP_DOWNSTREAMPORT_PRESENT], sizeof(u8))) {
> > + DRM_DEBUG_KMS("DPCD: new value for DPCD Downstream Port Present previous value %2x new value %2x\n",
> > + intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT],
> > + dpcd_ext[DP_DOWNSTREAMPORT_PRESENT]);
> > + memcpy(&intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT],
> > + &dpcd_ext[DP_DOWNSTREAMPORT_PRESENT],
> > + sizeof(u8));
> > + }
> > + }
> > +}
> > +
> > +
> > bool
> > intel_dp_read_dpcd(struct intel_dp *intel_dp)
> > {
> > @@ -3738,6 +3794,8 @@ intel_dp_read_dpcd(struct intel_dp *intel_dp)
> > sizeof(intel_dp->dpcd)) < 0)
> > return false; /* aux transfer failed */
> >
> > + intel_dp_extended_receiver_capabilities(intel_dp);
> > +
> > DRM_DEBUG_KMS("DPCD: %*ph\n", (int) sizeof(intel_dp->dpcd), intel_dp->dpcd);
> >
> > return intel_dp->dpcd[DP_DPCD_REV] != 0;
> > --
> > 2.17.1
> >