linux-kernel - Re: [PATCH 5/7] phy: qcom-qmp-combo: Introduce drm

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Date:   Wed, 26 Apr 2023 11:33:40 +0100
From:   "Bryan O'Donoghue" <pure.logic@...us-software.ie>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Johan Hovold <johan@...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
Subject: Re: [PATCH 5/7] phy: qcom-qmp-combo: Introduce drm_bridge

On Tue, Apr 25, 2023 at 4:40 AM Bjorn Andersson
<quic_bjorande@...cinc.com> 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>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 36 +++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
> index 5d6d6ef3944b..84bc08002537 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
> @@ -22,6 +22,8 @@
>  #include <linux/usb/typec.h>
>  #include <linux/usb/typec_mux.h>
>
> +#include <drm/drm_bridge.h>
> +
>  #include <dt-bindings/phy/phy-qcom-qmp.h>
>
>  #include "phy-qcom-qmp.h"
> @@ -1332,6 +1334,8 @@ struct qmp_combo {
>         struct clk_hw dp_link_hw;
>         struct clk_hw dp_pixel_hw;
>
> +       struct drm_bridge bridge;
> +
>         struct typec_switch_dev *sw;
>         enum typec_orientation orientation;
>  };
> @@ -3196,6 +3200,34 @@ static int qmp_combo_register_clocks(struct qmp_combo *qmp, struct device_node *
>         return devm_add_action_or_reset(qmp->dev, phy_clk_release_provider, dp_np);
>  }
>
> +static int qmp_combo_bridge_attach(struct drm_bridge *bridge,
> +                                  enum drm_bridge_attach_flags flags)
> +{
> +       struct qmp_combo *qmp = container_of(bridge, struct qmp_combo, bridge);
> +       struct drm_bridge *next_bridge;
> +
> +       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> +               return -EINVAL;
> +
> +       next_bridge = devm_drm_of_get_bridge(qmp->dev, qmp->dev->of_node, 0, 0);
> +       if (IS_ERR(next_bridge))
> +               return dev_err_probe(qmp->dev, PTR_ERR(next_bridge), "failed to acquire drm_bridge\n");
> +
> +       return drm_bridge_attach(bridge->encoder, next_bridge, bridge, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +}
> +
> +static const struct drm_bridge_funcs qmp_combo_bridge_funcs = {
> +       .attach = qmp_combo_bridge_attach,
> +};
> +
> +static int qmp_combo_dp_register_bridge(struct qmp_combo *qmp)
> +{
> +       qmp->bridge.funcs = &qmp_combo_bridge_funcs;
> +       qmp->bridge.of_node = qmp->dev->of_node;
> +
> +       return devm_drm_bridge_add(qmp->dev, &qmp->bridge);
> +}
> +
>  static int qmp_combo_parse_dt_lecacy_dp(struct qmp_combo *qmp, struct device_node *np)
>  {
>         struct device *dev = qmp->dev;
> @@ -3459,6 +3491,10 @@ static int qmp_combo_probe(struct platform_device *pdev)
>         if (ret)
>                 return ret;
>
> +       ret = qmp_combo_dp_register_bridge(qmp);
> +       if (ret)
> +               return ret;
> +
>         /* Check for legacy binding with child nodes. */
>         usb_np = of_get_child_by_name(dev->of_node, "usb3-phy");
>         if (usb_np) {
> --
> 2.39.2
>

You need to add some or all of these
       select DRM_DISPLAY_DP_HELPER
       select DRM_DISPLAY_HELPER
       select DRM_DP_AUX_BUS
       select DRM_KMS_HELPER
       select DRM_MIPI_DSI
       select DRM_PANEL


/opt/linaro/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-ld:
Unexpected GOT/PLT entries detected!
/opt/linaro/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-ld:
Unexpected run-time procedure linkages detected!
drivers/phy/qualcomm/phy-qcom-qmp-combo.o: In function
`qmp_combo_bridge_attach':
phy-qcom-qmp-combo.c:(.text+0xb50): undefined reference to
`devm_drm_of_get_bridge'
phy-qcom-qmp-combo.c:(.text+0xb6c): undefined reference to `drm_bridge_attach'
drivers/phy/qualcomm/phy-qcom-qmp-combo.o: In function `qmp_combo_probe':
phy-qcom-qmp-combo.c:(.text+0x13fc): undefined reference to
`devm_drm_bridge_add'

---
bod