[PATCH v9 3/9] drm/display: Add Type-C switch helpers

[Chen-Yu Tsai]

On Mon, Jan 9, 2023 at 4:41 PM Pin-yen Lin <treapking at chromium.org> 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 at chromium.org>

Tested-by: Chen-Yu Tsai <wenst at chromium.org>

on MT8192 based Hayato (ASUS Chromebook Flip CM3200).

> ---
>
> (no changes since v8)
>
> 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 | 132 ++++++++++++++++++++++++
>  include/drm/display/drm_dp_helper.h     |  16 +++
>  2 files changed, 148 insertions(+)
>
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index 16565a0a5da6..fb9e23744c08 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 +3893,133 @@ 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, void *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);
> +       if (num_lanes <= 0) {
> +               dev_err(dev, "Error on getting data lanes count: %d\n",
> +                       num_lanes);

Also printing out the full node name (endpoint at N) would be more helpful.

> +               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: %d\n",
> +                       ret);

Same here.

> +               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;
> +}
> +
> +/**
> + * 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, void *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_warn(dev, "No Type-C switches node found\n");

Maybe change this to dev_info or even dev_debug? A warning would be too
noisy if the bridge drivers are calling this helper unconditionally.

Otherwise,

Reviewed-by: Chen-Yu Tsai <wenst at chromium.org>