Re: [PATCH 5/7] phy: qcom-qmp-combo: Introduce drm_bridge

Johan Hovold
2023-05-02T12:05:56Z

On Mon, Apr 24, 2023 at 08:40:08PM -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@quicinc.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");

Using dev_err_probe() in an attach callback looks wrong as these
functions should not be returning -EPROBE_DEFER (and this is not a probe
function).

> +
> + return drm_bridge_attach(bridge->encoder, next_bridge, bridge, DRM_BRIDGE_ATTACH_NO_CONNECTOR);

This line is over 100 chars, but there should be no reason not to break
it before 80 here.

> +}
> +
> +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);
> +}

Guess you need a dummy function also for qmp_combo_dp_register_bridge()
in case of !CONFIG_DRM.

> +
> 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) {

Johan