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

[Chen-Yu Tsai <wenst@chromium.org>]

On Mon, Jan 9, 2023 at 6:10 PM Chen-Yu Tsai <wenst@chromium.org> wrote:
>
> On Mon, Jan 9, 2023 at 4:41 PM Pin-yen Lin <treapking@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@chromium.org>
>
> Tested-by: Chen-Yu Tsai <wenst@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)

Using "typec_mux_set_fn_t" instead of "void *" for mux_set would be
more explicit. Same for all the other instances where this parameter
gets declared.

ChenYu


> > +{
> > +       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@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@chromium.org>