linux-kernel - Re: [PATCH v3 2/5] drm/dp: fix link probing for devices supporting DP 1.4+

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Message-Id: <20180913110829eucas1p2de1f7f14c8dcf186d4b829c22920365e~T8Qbh1iEV3205832058eucas1p2W@eucas1p2.samsung.com>
Date:   Thu, 13 Sep 2018 13:08:27 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Damian Kos <dkos@...ence.com>, David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <sean@...rly.run>, Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        Quentin Schulz <quentin.schulz@...tlin.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Cc:     pgaj@...ence.com, ltyrala@...ence.com, stelford@...ence.com,
        jartur@...ence.com, piotrs@...ence.com
Subject: Re: [PATCH v3 2/5] drm/dp: fix link probing for devices supporting
 DP 1.4+

On 28.08.2018 12:24, Damian Kos wrote:
> From: Quentin Schulz <quentin.schulz@...tlin.com>
>
> DP 1.4 introduced a DP_EXTENDED_RCVR_CAPA_FIELD_PRESENT bit in
> DP_TRAINING_AUX_RD_INTERVAL register. If set, DPCD registers from DP_DPCD_REV
> to DP_ADAPTER_CAP should be retrieved starting from DP_DPCD_REV_EXTENDED.
> All registers are copied except DP_DPCD_REV, DP_MAX_LINK_RATE and
> DP_DOWNSTREAMPORT_PRESENT which represent the "true capabilities" of DPRX
> device.
>
> Original DP_DPCD_REV, DP_MAX_LINK_RATE and DP_DOWNSTREAMPORT_PRESENT might
> falsely return lower capabilities to "avoid interoperability issues with some
> of the existing DP Source devices that malfunction when they discover the
> higher capabilities within those three registers.".
>
> Before DP 1.4, DP_EXTENDED_RCVR_CAPA_FIELD_PRESENT bit was reserved and read 0
> so it's safe to check against it even if DP revision is <1.4
>
> Signed-off-by: Damian Kos <dkos@...ence.com>

Here and in next patches signed-off-by of the author is missing.

With that fixed:
Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>

 --
Regards
Andrzej