Re: [PATCH] drm/dp: move intel_dp_vsc_sdp_pack() to generic helper

[Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>]

On 2/14/2024 12:15 AM, Dmitry Baryshkov wrote:
> On Wed, 14 Feb 2024 at 01:45, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > intel_dp_vsc_sdp_pack() can be re-used by other DRM drivers as well.
> > Lets move this to drm_dp_helper to achieve this.
> >
> > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
>
> My preference would be to have packing functions in
> drivers/video/hdmi.c, as we already have
> hdmi_audio_infoframe_pack_for_dp() there.

My preference is drm_dp_helper because it already has some VSC SDP stuff 
and after discussion with Ville on IRC, I decided to post it this way.

hdmi_audio_infoframe_pack_for_dp() is an exception from my PoV as the 
hdmi audio infoframe fields were re-used and packed into a DP SDP 
thereby re-using the existing struct hdmi_audio_infoframe .

This is not like that. Here we pack from struct drm_dp_vsc_sdp to struct 
dp_sdp both of which had prior usages already in this file.

So it all adds up and makes sense to me to be in this file.

I will let the other DRM core maintainers comment on this.

Ville, Jani?

> > ---
> >   drivers/gpu/drm/display/drm_dp_helper.c | 78 +++++++++++++++++++++++++
> >   drivers/gpu/drm/i915/display/intel_dp.c | 73 +----------------------
> >   include/drm/display/drm_dp_helper.h     |  3 +
> >   3 files changed, 84 insertions(+), 70 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> > index b1ca3a1100da..066cfbbf7a91 100644
> > --- a/drivers/gpu/drm/display/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> > @@ -2916,6 +2916,84 @@ void drm_dp_vsc_sdp_log(const char *level, struct device *dev,
> >   }
> >   EXPORT_SYMBOL(drm_dp_vsc_sdp_log);
> >
> > +/**
> > + * drm_dp_vsc_sdp_pack() - pack a given vsc sdp into generic dp_sdp
> > + * @vsc: vsc sdp initialized according to its purpose as defined in
> > + *       table 2-118 - table 2-120 in DP 1.4a specification
> > + * @sdp: valid handle to the generic dp_sdp which will be packed
> > + * @size: valid size of the passed sdp handle
> > + *
> > + * Returns length of sdp on success and error code on failure
> > + */
> > +ssize_t drm_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc,
> > +                           struct dp_sdp *sdp, size_t size)
>
> I know that you are just moving the function. Maybe there can be
> patch#2, which drops the size argument? The struct dp_sdp already has
> a defined size. The i915 driver just passes sizeof(sdp), which is more
> or less useless.

Yes this is a valid point, I also noticed this. I can post it on top of 
this once we get an agreement and ack on this patch first.

> > +{
> > +       size_t length = sizeof(struct dp_sdp);
> > +
> > +       if (size < length)
> > +               return -ENOSPC;
> > +
> > +       memset(sdp, 0, size);
> > +
> > +       /*
> > +        * Prepare VSC Header for SU as per DP 1.4a spec, Table 2-119
> > +        * VSC SDP Header Bytes
> > +        */
> > +       sdp->sdp_header.HB0 = 0; /* Secondary-Data Packet ID = 0 */
> > +       sdp->sdp_header.HB1 = vsc->sdp_type; /* Secondary-data Packet Type */
> > +       sdp->sdp_header.HB2 = vsc->revision; /* Revision Number */
> > +       sdp->sdp_header.HB3 = vsc->length; /* Number of Valid Data Bytes */
> > +
> > +       if (vsc->revision == 0x6) {
> > +               sdp->db[0] = 1;
> > +               sdp->db[3] = 1;
> > +       }
> > +
> > +       /*
> > +        * Revision 0x5 and revision 0x7 supports Pixel Encoding/Colorimetry
> > +        * Format as per DP 1.4a spec and DP 2.0 respectively.
> > +        */
> > +       if (!(vsc->revision == 0x5 || vsc->revision == 0x7))
> > +               goto out;
> > +
> > +       /* VSC SDP Payload for DB16 through DB18 */
> > +       /* Pixel Encoding and Colorimetry Formats  */
> > +       sdp->db[16] = (vsc->pixelformat & 0xf) << 4; /* DB16[7:4] */
> > +       sdp->db[16] |= vsc->colorimetry & 0xf; /* DB16[3:0] */
> > +
> > +       switch (vsc->bpc) {
> > +       case 6:
> > +               /* 6bpc: 0x0 */
> > +               break;
> > +       case 8:
> > +               sdp->db[17] = 0x1; /* DB17[3:0] */
> > +               break;
> > +       case 10:
> > +               sdp->db[17] = 0x2;
> > +               break;
> > +       case 12:
> > +               sdp->db[17] = 0x3;
> > +               break;
> > +       case 16:
> > +               sdp->db[17] = 0x4;
> > +               break;
> > +       default:
> > +               WARN(1, "Missing case %d\n", vsc->bpc);
> > +               return -EINVAL;
> > +       }
> > +
> > +       /* Dynamic Range and Component Bit Depth */
> > +       if (vsc->dynamic_range == DP_DYNAMIC_RANGE_CTA)
> > +               sdp->db[17] |= 0x80;  /* DB17[7] */
> > +
> > +       /* Content Type */
> > +       sdp->db[18] = vsc->content_type & 0x7;
> > +
> > +out:
> > +       return length;
> > +}
> > +EXPORT_SYMBOL(drm_dp_vsc_sdp_pack);
> > +
> >   /**
> >    * drm_dp_get_pcon_max_frl_bw() - maximum frl supported by PCON
> >    * @dpcd: DisplayPort configuration data
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index f5ef95da5534..e94db51aeeb7 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -4110,73 +4110,6 @@ intel_dp_needs_vsc_sdp(const struct intel_crtc_state *crtc_state,
> >          return false;
> >   }
> >
> > -static ssize_t intel_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc,
> > -                                    struct dp_sdp *sdp, size_t size)
> > -{
> > -       size_t length = sizeof(struct dp_sdp);
> > -
> > -       if (size < length)
> > -               return -ENOSPC;
> > -
> > -       memset(sdp, 0, size);
> > -
> > -       /*
> > -        * Prepare VSC Header for SU as per DP 1.4a spec, Table 2-119
> > -        * VSC SDP Header Bytes
> > -        */
> > -       sdp->sdp_header.HB0 = 0; /* Secondary-Data Packet ID = 0 */
> > -       sdp->sdp_header.HB1 = vsc->sdp_type; /* Secondary-data Packet Type */
> > -       sdp->sdp_header.HB2 = vsc->revision; /* Revision Number */
> > -       sdp->sdp_header.HB3 = vsc->length; /* Number of Valid Data Bytes */
> > -
> > -       if (vsc->revision == 0x6) {
> > -               sdp->db[0] = 1;
> > -               sdp->db[3] = 1;
> > -       }
> > -
> > -       /*
> > -        * Revision 0x5 and revision 0x7 supports Pixel Encoding/Colorimetry
> > -        * Format as per DP 1.4a spec and DP 2.0 respectively.
> > -        */
> > -       if (!(vsc->revision == 0x5 || vsc->revision == 0x7))
> > -               goto out;
> > -
> > -       /* VSC SDP Payload for DB16 through DB18 */
> > -       /* Pixel Encoding and Colorimetry Formats  */
> > -       sdp->db[16] = (vsc->pixelformat & 0xf) << 4; /* DB16[7:4] */
> > -       sdp->db[16] |= vsc->colorimetry & 0xf; /* DB16[3:0] */
> > -
> > -       switch (vsc->bpc) {
> > -       case 6:
> > -               /* 6bpc: 0x0 */
> > -               break;
> > -       case 8:
> > -               sdp->db[17] = 0x1; /* DB17[3:0] */
> > -               break;
> > -       case 10:
> > -               sdp->db[17] = 0x2;
> > -               break;
> > -       case 12:
> > -               sdp->db[17] = 0x3;
> > -               break;
> > -       case 16:
> > -               sdp->db[17] = 0x4;
> > -               break;
> > -       default:
> > -               MISSING_CASE(vsc->bpc);
> > -               break;
> > -       }
> > -       /* Dynamic Range and Component Bit Depth */
> > -       if (vsc->dynamic_range == DP_DYNAMIC_RANGE_CTA)
> > -               sdp->db[17] |= 0x80;  /* DB17[7] */
> > -
> > -       /* Content Type */
> > -       sdp->db[18] = vsc->content_type & 0x7;
> > -
> > -out:
> > -       return length;
> > -}
> > -
> >   static ssize_t
> >   intel_dp_hdr_metadata_infoframe_sdp_pack(struct drm_i915_private *i915,
> >                                           const struct hdmi_drm_infoframe *drm_infoframe,
> > @@ -4269,8 +4202,8 @@ static void intel_write_dp_sdp(struct intel_encoder *encoder,
> >
> >          switch (type) {
> >          case DP_SDP_VSC:
> > -               len = intel_dp_vsc_sdp_pack(&crtc_state->infoframes.vsc, &sdp,
> > -                                           sizeof(sdp));
> > +               len = drm_dp_vsc_sdp_pack(&crtc_state->infoframes.vsc, &sdp,
> > +                                         sizeof(sdp));
> >                  break;
> >          case HDMI_PACKET_TYPE_GAMUT_METADATA:
> >                  len = intel_dp_hdr_metadata_infoframe_sdp_pack(dev_priv,
> > @@ -4297,7 +4230,7 @@ void intel_write_dp_vsc_sdp(struct intel_encoder *encoder,
> >          struct dp_sdp sdp = {};
> >          ssize_t len;
> >
> > -       len = intel_dp_vsc_sdp_pack(vsc, &sdp, sizeof(sdp));
> > +       len = drm_dp_vsc_sdp_pack(vsc, &sdp, sizeof(sdp));
> >
> >          if (drm_WARN_ON(&dev_priv->drm, len < 0))
> >                  return;
> > diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> > index 863b2e7add29..f8db34a2f7a5 100644
> > --- a/include/drm/display/drm_dp_helper.h
> > +++ b/include/drm/display/drm_dp_helper.h
> > @@ -813,4 +813,7 @@ int drm_dp_bw_overhead(int lane_count, int hactive,
> >                         int bpp_x16, unsigned long flags);
> >   int drm_dp_bw_channel_coding_efficiency(bool is_uhbr);
> >
> > +ssize_t drm_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc,
> > +                           struct dp_sdp *sdp, size_t size);
> > +
> >   #endif /* _DRM_DP_HELPER_H_ */
> > --
> > 2.34.1