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

[Dmitry Baryshkov]

On 27/04/2023 16:11, Neil Armstrong wrote:
> On 26/04/2023 12:33, Bryan O'Donoghue wrote:
> > On Tue, Apr 25, 2023 at 4:40 AM Bjorn Andersson
> > <quic_bjorande@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > > ---
> > >   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;
>
> I think the DRM part should be only built if CONFIG_DRM is enabled, I don't
> have a strong opinion on this, I think Vinod could help here.
>
> > > +
> > >          /* 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'
>
> I think CONFIG_DRM_PANEL_BRIDGE in addition to CONFIG_DRM. should be 
> enough.

I'd say DRM_PANEL_BRIDGE || !DRM_PANEL_BRIDGE in addition to DRM. And we 
probably should fix the  devm_drm_of_get_bridge() stub to use 
drm_of_find_panel_or_bridge() with panel = NULL.

> With this config added and my drm-bridge hat:
>
> Acked-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
>
> Neil
>
>
> > ---
> > bod

--
With best wishes
Dmitry