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[166.177.185.175]) by smtp.gmail.com with ESMTPSA id u21sm22277690qkk.1.2020.08.19.08.15.58 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 19 Aug 2020 08:15:58 -0700 (PDT) Date: Wed, 19 Aug 2020 11:15:53 -0400 From: Sean Paul To: Lyude Paul Cc: nouveau@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Thomas Zimmermann , David Airlie , Lucas De Marchi , open list , Gwan-gyeong Mun , Manasi Navare , Uma Shankar , Rodrigo Vivi , =?iso-8859-1?Q?Jos=E9?= Roberto de Souza , Wambui Karuga Subject: Re: [RFC 13/20] drm/i915/dp: Extract drm_dp_downstream_read_info() Message-ID: <20200819151547.GB46474@art_vandelay> References: <20200811200457.134743-1-lyude@redhat.com> <20200811200457.134743-14-lyude@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200811200457.134743-14-lyude@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 11, 2020 at 04:04:50PM -0400, Lyude Paul wrote: > We're going to be doing the same probing process in nouveau for > determining downstream DP port capabilities, so let's deduplicate the > work by moving i915's code for handling this into a shared helper: > drm_dp_downstream_read_info(). > > Note that when we do this, we also do make some functional changes while > we're at it: > * We always clear the downstream port info before trying to read it, > just to make things easier for the caller > * We skip reading downstream port info if the DPCD indicates that we > don't support downstream port info > * We only read as many bytes as needed for the reported number of > downstream ports, no sense in reading the whole thing every time > > Signed-off-by: Lyude Paul > --- > drivers/gpu/drm/drm_dp_helper.c | 32 +++++++++++++++++++++++++ > drivers/gpu/drm/i915/display/intel_dp.c | 14 ++--------- > include/drm/drm_dp_helper.h | 3 +++ > 3 files changed, 37 insertions(+), 12 deletions(-) > > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c > index 4c21cf69dad5a..9703b33599c3b 100644 > --- a/drivers/gpu/drm/drm_dp_helper.c > +++ b/drivers/gpu/drm/drm_dp_helper.c > @@ -423,6 +423,38 @@ bool drm_dp_send_real_edid_checksum(struct drm_dp_aux *aux, > } > EXPORT_SYMBOL(drm_dp_send_real_edid_checksum); > > +/** > + * drm_dp_downstream_read_info() - read DPCD downstream port info if available > + * @aux: DisplayPort AUX channel > + * @dpcd: A cached copy of the port's DPCD > + * @downstream_ports: buffer to store the downstream port info in > + * > + * Returns: 0 if either the downstream port info was read successfully or > + * there was no downstream info to read, or a negative error code otherwise. > + */ > +int drm_dp_downstream_read_info(struct drm_dp_aux *aux, > + const u8 dpcd[DP_RECEIVER_CAP_SIZE], > + u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS]) > +{ > + int ret; > + u8 len; > + > + memset(downstream_ports, 0, DP_MAX_DOWNSTREAM_PORTS); > + > + /* No downstream info to read */ > + if (!drm_dp_is_branch(dpcd) || > + dpcd[DP_DPCD_REV] < DP_DPCD_REV_10 || > + !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT)) > + return 0; > + > + len = (dpcd[DP_DOWN_STREAM_PORT_COUNT] & DP_PORT_COUNT_MASK) * 4; I'm having a hard time rationalizing DP_MAX_DOWNSTREAM_PORTS being 16, but only having 4 ports worth of data in the DP_DOWNSTREAM_PORT_* registers. Do you know what's supposed to happen if dpcd[DP_DOWN_STREAM_PORT_COUNT] is > 4? Sean > + ret = drm_dp_dpcd_read(aux, DP_DOWNSTREAM_PORT_0, downstream_ports, > + len); > + > + return ret == len ? 0 : -EIO; > +} > +EXPORT_SYMBOL(drm_dp_downstream_read_info); > + > /** > * drm_dp_downstream_max_clock() - extract branch device max > * pixel rate for legacy VGA > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 1e29d3a012856..984e49194ca31 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -4685,18 +4685,8 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp) > return false; > } > > - if (!drm_dp_is_branch(intel_dp->dpcd)) > - return true; /* native DP sink */ > - > - if (intel_dp->dpcd[DP_DPCD_REV] == 0x10) > - return true; /* no per-port downstream info */ > - > - if (drm_dp_dpcd_read(&intel_dp->aux, DP_DOWNSTREAM_PORT_0, > - intel_dp->downstream_ports, > - DP_MAX_DOWNSTREAM_PORTS) < 0) > - return false; /* downstream port status fetch failed */ > - > - return true; > + return drm_dp_downstream_read_info(&intel_dp->aux, intel_dp->dpcd, > + intel_dp->downstream_ports) == 0; > } > > static bool > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h > index 5c28199248626..1349f16564ace 100644 > --- a/include/drm/drm_dp_helper.h > +++ b/include/drm/drm_dp_helper.h > @@ -1613,6 +1613,9 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, > bool drm_dp_send_real_edid_checksum(struct drm_dp_aux *aux, > u8 real_edid_checksum); > > +int drm_dp_downstream_read_info(struct drm_dp_aux *aux, > + const u8 dpcd[DP_RECEIVER_CAP_SIZE], > + u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS]); > int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE], > const u8 port_cap[4]); > int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE], > -- > 2.26.2 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Sean Paul, Software Engineer, Google / Chromium OS