linux-kernel - Re: [PATCH v2 6/8] phy: qcom-qmp-combo: Introduce drm

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Message-ID: <ZF4Izb0WHvfSPK9H@hovoldconsulting.com>
Date:   Fri, 12 May 2023 11:37:17 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Abel Vesa <abel.vesa@...aro.org>,
        Steev Klimaszewski <steev@...i.org>,
        Johan Hovold <johan+linaro@...nel.org>
Subject: Re: [PATCH v2 6/8] phy: qcom-qmp-combo: Introduce drm_bridge

On Tue, May 09, 2023 at 08:19:28PM -0700, Bjorn Andersson wrote:
> The QMP combo PHY sits in an of_graph connected between the DisplayPort
> controller and a USB Type-C connector (or possibly a redriver).
> 
> The TCPM needs to be able to convey the HPD signal to the DisplayPort
> controller, but no directly link is provided by DeviceTree so the signal
> needs to "pass through" the QMP combo phy.
> 
> Handle this by introducing a drm_bridge which upon initialization finds
> the next bridge (i.e. the usb-c-connector) and chain this together. This
> way HPD changes in the connector will propagate to the DisplayPort
> driver.
> 
> The connector bridge is resolved lazily, as the TCPM is expected to be
> able to resolve the typec mux and switch at probe time, so the QMP combo
> phy will probe before the TCPM.
> 
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> Acked-by: Neil Armstrong <neil.armstrong@...aro.org>
> Tested-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> Tested-by: Abel Vesa <abel.vesa@...aro.org>
> Tested-by: Steev Klimaszewski <steev@...i.org>
> Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on HDK8450
> Tested-by: Johan Hovold <johan+linaro@...nel.org>	# X13s
> ---
> 
> Changes since v1:
> - Wrap DRM-related code in CONFIG_DRM guard
> - Inroduce DRM-dependencies in Kconfig
> - Dropped dev_err_probe() usage

Reviewed-by: Johan Hovold <johan+linaro@...nel.org>