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Message-ID: <501a431dce94fdaa086324ed6660b1188e1f3390.camel@redhat.com>
Date: Thu, 20 Aug 2020 12:49:41 -0400
From: Lyude Paul <lyude@...hat.com>
To: Sean Paul <sean@...rly.run>
Cc: nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org,
Thomas Zimmermann <tzimmermann@...e.de>,
Juha-Pekka Heikkila <juhapekka.heikkila@...il.com>,
David Airlie <airlied@...ux.ie>,
Lucas De Marchi <lucas.demarchi@...el.com>,
open list <linux-kernel@...r.kernel.org>,
Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>,
Manasi Navare <manasi.d.navare@...el.com>,
Uma Shankar <uma.shankar@...el.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
José Roberto de Souza
<jose.souza@...el.com>, Animesh Manna <animesh.manna@...el.com>,
Wambui Karuga <wambui.karugax@...il.com>
Subject: Re: [RFC 19/20] drm/i915/dp: Extract drm_dp_read_dpcd_caps()
On Wed, 2020-08-19 at 11:29 -0400, Sean Paul wrote:
> On Tue, Aug 11, 2020 at 04:04:56PM -0400, Lyude Paul wrote:
> > Since DP 1.3, it's been possible for DP receivers to specify an
> > additional set of DPCD capabilities, which can take precedence over the
> > capabilities reported at DP_DPCD_REV.
> >
> > Basically any device supporting DP is going to need to read these in an
> > identical manner, in particular nouveau, so let's go ahead and just move
> > this code out of i915 into a shared DRM DP helper that we can use in
> > other drivers.
> >
> > Signed-off-by: Lyude Paul <lyude@...hat.com>
> > ---
> > drivers/gpu/drm/drm_dp_helper.c | 76 +++++++++++++++++++++
> > drivers/gpu/drm/i915/display/intel_dp.c | 60 +---------------
> > drivers/gpu/drm/i915/display/intel_dp.h | 1 -
> > drivers/gpu/drm/i915/display/intel_lspcon.c | 2 +-
> > include/drm/drm_dp_helper.h | 3 +
> > 5 files changed, 82 insertions(+), 60 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c
> > b/drivers/gpu/drm/drm_dp_helper.c
> > index 0ff2959c8f8e8..f9445915c6c26 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -423,6 +423,82 @@ bool drm_dp_send_real_edid_checksum(struct drm_dp_aux
> > *aux,
> > }
> > EXPORT_SYMBOL(drm_dp_send_real_edid_checksum);
> >
> > +static int drm_dp_read_extended_dpcd_caps(struct drm_dp_aux *aux,
> > + u8 dpcd[DP_RECEIVER_CAP_SIZE])
> > +{
> > + u8 dpcd_ext[6];
> > + int ret;
> > +
> > + /*
> > + * 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 (!(dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
> > + DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT))
> > + return 0;
> > +
> > + ret = drm_dp_dpcd_read(aux, DP_DP13_DPCD_REV, &dpcd_ext,
> > + sizeof(dpcd_ext));
> > + if (ret != sizeof(dpcd_ext))
> > + return -EIO;
> > +
> > + if (dpcd[DP_DPCD_REV] > dpcd_ext[DP_DPCD_REV]) {
> > + DRM_DEBUG_KMS("%s: Extended DPCD rev less than base DPCD rev (%d
> > > %d)\n",
> > + aux->name, dpcd[DP_DPCD_REV],
> > + dpcd_ext[DP_DPCD_REV]);
>
> Might be a good opportunity to convert all of these to drm_dbg_dp()?
Oh also - thought about this as well, but this would be easier as a follow-up
patch since we'd want to add a backpointer to the original DRM device (not 100%
sure we can just determine the drm device parent from the aux device's parent)
>
> > + return 0;
> > + }
> > +
> > + if (!memcmp(dpcd, dpcd_ext, sizeof(dpcd_ext)))
> > + return 0;
> > +
> > + DRM_DEBUG_KMS("%s: Base DPCD: %*ph\n",
> > + aux->name, DP_RECEIVER_CAP_SIZE, dpcd);
> > +
> > + memcpy(dpcd, dpcd_ext, sizeof(dpcd_ext));
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * drm_dp_read_dpcd_caps() - read DPCD caps and extended DPCD caps if
> > + * available
> > + * @aux: DisplayPort AUX channel
> > + * @dpcd: Buffer to store the resulting DPCD in
> > + *
> > + * Attempts to read the base DPCD caps for @aux. Additionally, this
> > function
> > + * checks for and reads the extended DPRX caps (%DP_DP13_DPCD_REV) if
> > + * present.
> > + *
> > + * Returns: %0 if the DPCD was read successfully, negative error code
> > + * otherwise.
> > + */
> > +int drm_dp_read_dpcd_caps(struct drm_dp_aux *aux,
> > + u8 dpcd[DP_RECEIVER_CAP_SIZE])
> > +{
> > + int ret;
> > +
> > + ret = drm_dp_dpcd_read(aux, DP_DPCD_REV, dpcd, DP_RECEIVER_CAP_SIZE);
> > + if (ret != DP_RECEIVER_CAP_SIZE || dpcd[DP_DPCD_REV] == 0)
> > + return -EIO;
> > +
> > + ret = drm_dp_read_extended_dpcd_caps(aux, dpcd);
> > + if (ret < 0)
> > + return ret;
>
> I wonder if we should just go with the "regular" dpcd caps we just read in
> this
> case?
>
> Regardless of my nits,
>
> Reviewed-by: Sean Paul <sean@...rly.run>
>
> > +
> > + DRM_DEBUG_KMS("%s: DPCD: %*ph\n",
> > + aux->name, DP_RECEIVER_CAP_SIZE, dpcd);
> > +
> > + if (dpcd[DP_DPCD_REV] == 0)
> > + ret = -EIO;
> > +
> > + return ret;
> > +}
> > +EXPORT_SYMBOL(drm_dp_read_dpcd_caps);
> > +
> > /**
> > * drm_dp_downstream_read_info() - read DPCD downstream port info if
> > available
> > * @aux: DisplayPort AUX channel
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index e343965a483df..230aa0360dc61 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -4449,62 +4449,6 @@ intel_dp_link_down(struct intel_encoder *encoder,
> > }
> > }
> >
> > -static void
> > -intel_dp_extended_receiver_capabilities(struct intel_dp *intel_dp)
> > -{
> > - struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > - u8 dpcd_ext[6];
> > -
> > - /*
> > - * 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))
> > - return;
> > -
> > - if (drm_dp_dpcd_read(&intel_dp->aux, DP_DP13_DPCD_REV,
> > - &dpcd_ext, sizeof(dpcd_ext)) != sizeof(dpcd_ext)) {
> > - drm_err(&i915->drm,
> > - "DPCD failed read at extended capabilities\n");
> > - return;
> > - }
> > -
> > - if (intel_dp->dpcd[DP_DPCD_REV] > dpcd_ext[DP_DPCD_REV]) {
> > - drm_dbg_kms(&i915->drm,
> > - "DPCD extended DPCD rev less than base DPCD rev\n");
> > - return;
> > - }
> > -
> > - if (!memcmp(intel_dp->dpcd, dpcd_ext, sizeof(dpcd_ext)))
> > - return;
> > -
> > - drm_dbg_kms(&i915->drm, "Base DPCD: %*ph\n",
> > - (int)sizeof(intel_dp->dpcd), intel_dp->dpcd);
> > -
> > - memcpy(intel_dp->dpcd, dpcd_ext, sizeof(dpcd_ext));
> > -}
> > -
> > -bool
> > -intel_dp_read_dpcd(struct intel_dp *intel_dp)
> > -{
> > - struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -
> > - if (drm_dp_dpcd_read(&intel_dp->aux, 0x000, intel_dp->dpcd,
> > - sizeof(intel_dp->dpcd)) < 0)
> > - return false; /* aux transfer failed */
> > -
> > - intel_dp_extended_receiver_capabilities(intel_dp);
> > -
> > - drm_dbg_kms(&i915->drm, "DPCD: %*ph\n", (int)sizeof(intel_dp->dpcd),
> > - intel_dp->dpcd);
> > -
> > - return intel_dp->dpcd[DP_DPCD_REV] != 0;
> > -}
> > -
> > bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp)
> > {
> > u8 dprx = 0;
> > @@ -4563,7 +4507,7 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
> > /* this function is meant to be called only once */
> > drm_WARN_ON(&dev_priv->drm, intel_dp->dpcd[DP_DPCD_REV] != 0);
> >
> > - if (!intel_dp_read_dpcd(intel_dp))
> > + if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd) != 0)
> > return false;
> >
> > drm_dp_read_desc(&intel_dp->aux, &intel_dp->desc,
> > @@ -4650,7 +4594,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> > {
> > int ret;
> >
> > - if (!intel_dp_read_dpcd(intel_dp))
> > + if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd))
> > return false;
> >
> > /*
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> > b/drivers/gpu/drm/i915/display/intel_dp.h
> > index b901ab850cbd9..0a3af3410d52e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.h
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> > @@ -99,7 +99,6 @@ bool intel_dp_source_supports_hbr3(struct intel_dp
> > *intel_dp);
> > bool
> > intel_dp_get_link_status(struct intel_dp *intel_dp, u8 *link_status);
> >
> > -bool intel_dp_read_dpcd(struct intel_dp *intel_dp);
> > bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp);
> > int intel_dp_link_required(int pixel_clock, int bpp);
> > int intel_dp_max_data_rate(int max_link_clock, int max_lanes);
> > diff --git a/drivers/gpu/drm/i915/display/intel_lspcon.c
> > b/drivers/gpu/drm/i915/display/intel_lspcon.c
> > index b781bf4696443..dc1b35559afdf 100644
> > --- a/drivers/gpu/drm/i915/display/intel_lspcon.c
> > +++ b/drivers/gpu/drm/i915/display/intel_lspcon.c
> > @@ -571,7 +571,7 @@ bool lspcon_init(struct intel_digital_port *dig_port)
> > return false;
> > }
> >
> > - if (!intel_dp_read_dpcd(dp)) {
> > + if (drm_dp_read_dpcd_caps(&dp->aux, dp->dpcd) != 0) {
> > DRM_ERROR("LSPCON DPCD read failed\n");
> > return false;
> > }
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index 0c141fc81aaa8..11649e93e5bb6 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -1607,6 +1607,9 @@ static inline ssize_t drm_dp_dpcd_writeb(struct
> > drm_dp_aux *aux,
> > return drm_dp_dpcd_write(aux, offset, &value, 1);
> > }
> >
> > +int drm_dp_read_dpcd_caps(struct drm_dp_aux *aux,
> > + u8 dpcd[DP_RECEIVER_CAP_SIZE]);
> > +
> > int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
> > u8 status[DP_LINK_STATUS_SIZE]);
> >
> > --
> > 2.26.2
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Sincerely,
Lyude Paul (she/her)
Software Engineer at Red Hat
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