Re: [PATCH v10 3/9] drm/display: Add Type-C switch helpers

[Pin-yen Lin]

Hi Dmitry,

Thanks for the review.

On Thu, Jan 12, 2023 at 12:40 PM Dmitry Baryshkov
<dmitry.baryshkov@xxxxxxxxxx> wrote:
>
> On 12/01/2023 06:20, Pin-yen Lin wrote:
> > Add helpers to register and unregister Type-C "switches" for bridges
> > capable of switching their output between two downstream devices.
> >
> > The helper registers USB Type-C mode switches when the "mode-switch"
> > and the "data-lanes" properties are available in Device Tree.
> >
> > Signed-off-by: Pin-yen Lin <treapking@xxxxxxxxxxxx>
> > Tested-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> > Reviewed-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> > Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> >
> > ---
> >
> > Changes in v10:
> > - Collected Reviewed-by and Tested-by tags
> > - Replaced "void *" with "typec_mux_set_fn_t" for mux_set callbacks
> > - Print out the node name when errors on parsing DT
> > - Use dev_dbg instead of dev_warn when no Type-C switch nodes available
> > - Made the return path of drm_dp_register_mode_switch clearer
> >
> > Changes in v8:
> > - Fixed the build issue when CONFIG_TYPEC=m
> > - Fixed some style issues
> >
> > Changes in v7:
> > - Extracted the common codes to a helper function
> > - New in v7
> >
> >   drivers/gpu/drm/display/drm_dp_helper.c | 134 ++++++++++++++++++++++++
> >   include/drm/display/drm_dp_helper.h     |  17 +++
> >   2 files changed, 151 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> > index 16565a0a5da6..a2ec40a621cb 100644
> > --- a/drivers/gpu/drm/display/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> > @@ -30,11 +30,13 @@
> >   #include <linux/sched.h>
> >   #include <linux/seq_file.h>
> >   #include <linux/string_helpers.h>
> > +#include <linux/usb/typec_mux.h>
> >   #include <linux/dynamic_debug.h>
> >
> >   #include <drm/display/drm_dp_helper.h>
> >   #include <drm/display/drm_dp_mst_helper.h>
> >   #include <drm/drm_edid.h>
> > +#include <drm/drm_of.h>
> >   #include <drm/drm_print.h>
> >   #include <drm/drm_vblank.h>
> >   #include <drm/drm_panel.h>
> > @@ -3891,3 +3893,135 @@ int drm_panel_dp_aux_backlight(struct drm_panel *panel, struct drm_dp_aux *aux)
> >   EXPORT_SYMBOL(drm_panel_dp_aux_backlight);
> >
> >   #endif
> > +
> > +#if IS_REACHABLE(CONFIG_TYPEC)
> > +static int drm_dp_register_mode_switch(struct device *dev, struct device_node *node,
> > +                                    struct drm_dp_typec_switch_desc *switch_desc,
> > +                                    void *data, typec_mux_set_fn_t mux_set)
> > +{
> > +     struct drm_dp_typec_port_data *port_data;
> > +     struct typec_mux_desc mux_desc = {};
> > +     char name[32];
> > +     u32 dp_lanes[2];
> > +     int ret, num_lanes, port_num = -1;
> > +
> > +     num_lanes = drm_of_get_data_lanes_count(node, 0, 2);
>
> 2 looks incorrect. IIRC DP altmode can support up to 4 lanes.

This function is implemented for 4-lane DP bridges to switch its
outputs between 2 downstreams. So, I assume that there will only be at
most 2 lanes for each downstream. I don't think a 4-lane downstream
makes sense for mode switches unless we want to support bridges with
more than 4 lanes.
>
> > +     if (num_lanes <= 0) {
> > +             dev_err(dev, "Error on getting data lanes count from %s: %d\n",
> > +                     node->name, num_lanes);
> > +             return num_lanes;
> > +     }
> > +
> > +     ret = of_property_read_u32_array(node, "data-lanes", dp_lanes, num_lanes);
> > +     if (ret) {
> > +             dev_err(dev, "Failed to read the data-lanes variable from %s: %d\n",
> > +                     node->name, ret);
> > +             return ret;
> > +     }
> > +
> > +     port_num = dp_lanes[0] / 2;
> > +
> > +     port_data = &switch_desc->typec_ports[port_num];
> > +     port_data->data = data;
> > +     mux_desc.fwnode = &node->fwnode;
> > +     mux_desc.drvdata = port_data;
> > +     snprintf(name, sizeof(name), "%s-%u", node->name, port_num);
> > +     mux_desc.name = name;
> > +     mux_desc.set = mux_set;
> > +
> > +     port_data->typec_mux = typec_mux_register(dev, &mux_desc);
> > +     if (IS_ERR(port_data->typec_mux)) {
> > +             ret = PTR_ERR(port_data->typec_mux);
> > +             dev_err(dev, "Mode switch register for port %d failed: %d\n",
> > +                     port_num, ret);
> > +
> > +             return ret;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +/**
> > + * drm_dp_register_typec_switches() - register Type-C switches
> > + * @dev: Device that registers Type-C switches
> > + * @port: Device node for the switch
> > + * @switch_desc: A Type-C switch descriptor
> > + * @data: Private data for the switches
> > + * @mux_set: Callback function for typec_mux_set
> > + *
> > + * This function registers USB Type-C switches for DP bridges that can switch
> > + * the output signal between their output pins.
> > + *
> > + * Currently only mode switches are implemented, and the function assumes the
> > + * given @port device node has endpoints with "mode-switch" property.
> > + * Register the endpoint as port 0 if the "data-lanes" property falls in 0/1,
> > + * and register it as port 1 if "data-lanes" falls in 2/3.
> > + */
> > +int drm_dp_register_typec_switches(struct device *dev, struct device_node *port,
> > +                                struct drm_dp_typec_switch_desc *switch_desc,
> > +                                void *data, typec_mux_set_fn_t mux_set)
> > +{
> > +     struct device_node *sw;
> > +     int ret;
> > +
> > +     for_each_child_of_node(port, sw) {
> > +             if (of_property_read_bool(sw, "mode-switch"))
> > +                     switch_desc->num_typec_switches++;
> > +     }
> > +
> > +     if (!switch_desc->num_typec_switches) {
> > +             dev_dbg(dev, "No Type-C switches node found\n");
> > +             return 0;
> > +     }
> > +
> > +     switch_desc->typec_ports = devm_kcalloc(
> > +             dev, switch_desc->num_typec_switches,
> > +             sizeof(struct drm_dp_typec_port_data), GFP_KERNEL);
> > +
> > +     if (!switch_desc->typec_ports)
> > +             return -ENOMEM;
> > +
> > +     /* Register switches for each connector. */
> > +     for_each_child_of_node(port, sw) {
> > +             if (!of_property_read_bool(sw, "mode-switch"))
> > +                     continue;
> > +             ret = drm_dp_register_mode_switch(dev, sw, switch_desc, data, mux_set);
> > +             if (ret)
> > +                     goto err_unregister_typec_switches;
> > +     }
> > +
> > +     return 0;
> > +
> > +err_unregister_typec_switches:
> > +     of_node_put(sw);
> > +     drm_dp_unregister_typec_switches(switch_desc);
> > +     dev_err(dev, "Failed to register mode switch: %d\n", ret);
> > +     return ret;
> > +}
> > +EXPORT_SYMBOL(drm_dp_register_typec_switches);
> > +
> > +/**
> > + * drm_dp_unregister_typec_switches() - unregister Type-C switches
> > + * @switch_desc: A Type-C switch descriptor
> > + */
> > +void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc)
> > +{
> > +     int i;
> > +
> > +     for (i = 0; i < switch_desc->num_typec_switches; i++)
> > +             typec_mux_unregister(switch_desc->typec_ports[i].typec_mux);
> > +}
> > +EXPORT_SYMBOL(drm_dp_unregister_typec_switches);
> > +#else
> > +void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc)
> > +{
> > +}
> > +EXPORT_SYMBOL(drm_dp_register_typec_switches);
> > +int drm_dp_register_typec_switches(struct device *dev, struct device_node *port,
> > +                                struct drm_dp_typec_switch_desc *switch_desc,
> > +                                void *data, typec_mux_set_fn_t mux_set)
> > +{
> > +     return 0;
> > +}
> > +EXPORT_SYMBOL(drm_dp_unregister_typec_switches);
> > +#endif
> > diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> > index ab55453f2d2c..5a3824f13b4e 100644
> > --- a/include/drm/display/drm_dp_helper.h
> > +++ b/include/drm/display/drm_dp_helper.h
> > @@ -25,6 +25,7 @@
> >
> >   #include <linux/delay.h>
> >   #include <linux/i2c.h>
> > +#include <linux/usb/typec_mux.h>
> >
> >   #include <drm/display/drm_dp.h>
> >   #include <drm/drm_connector.h>
> > @@ -763,4 +764,20 @@ bool drm_dp_downstream_rgb_to_ycbcr_conversion(const u8 dpcd[DP_RECEIVER_CAP_SIZ
> >                                              const u8 port_cap[4], u8 color_spc);
> >   int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8 color_spc);
> >
> > +struct drm_dp_typec_port_data {
> > +     struct typec_mux_dev *typec_mux;
> > +     void *data;
> > +     bool dp_connected;
> > +};
> > +
> > +struct drm_dp_typec_switch_desc {
> > +     int num_typec_switches;
> > +     struct drm_dp_typec_port_data *typec_ports;
> > +};
> > +
> > +void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc);
> > +int drm_dp_register_typec_switches(struct device *dev, struct device_node *port,
> > +                                struct drm_dp_typec_switch_desc *switch_desc,
> > +                                void *data, typec_mux_set_fn_t mux_set);
> > +
> >   #endif /* _DRM_DP_HELPER_H_ */
>
> --
> With best wishes
> Dmitry
>

Best regards,
Pin-yen