Re: [PATCH v14 03/10] drm/display: Add Type-C switch helpers

[Dmitry Baryshkov]

On Wed, 22 Mar 2023 at 12:47, Pin-yen Lin <treapking@xxxxxxxxxxxx> 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 "reg" properties are available in Device Tree.
>
> Signed-off-by: Pin-yen Lin <treapking@xxxxxxxxxxxx>
>
> ---
>
> Changes in v14:
> - Introduce a new Kconfig becuase it didn't build when CONFIG_TYPEC=m
> - Add comments about devm_* usage
> - Fix style issues
>
> Changes in v13:
> - Add typec_mode_switch_node_count helper
> - Fix style issues
>
> Changes in v12:
> - Add fwnode_for_each_typec_mode_switch macro
> - Remove a duplicated dmesg in the helper
> - Used IS_REACHABLE instead to guard the function signatures
>
> Changes in v11:
> - Use fwnode helpers instead of DT
> - Moved the helpers to a new file
> - Use "reg" instead of "data-lanes" to determine the port number
> - Dropped collected tags due to new changes
>
> 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/Kconfig               |   8 ++
>  drivers/gpu/drm/display/Makefile              |   2 +
>  drivers/gpu/drm/display/drm_dp_typec_helper.c | 105 ++++++++++++++++++
>  include/drm/display/drm_dp_helper.h           |  46 ++++++++
>  4 files changed, 161 insertions(+)
>  create mode 100644 drivers/gpu/drm/display/drm_dp_typec_helper.c
>
> diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig
> index 09712b88a5b8..d61076947a1c 100644
> --- a/drivers/gpu/drm/display/Kconfig
> +++ b/drivers/gpu/drm/display/Kconfig
> @@ -29,6 +29,14 @@ config DRM_DISPLAY_HDMI_HELPER
>         help
>           DRM display helpers for HDMI.
>
> +config DRM_DISPLAY_DP_TYPEC_HELPER
> +       bool
> +       default y
> +       depends on DRM_DISPLAY_HELPER
> +       depends on DRM_DISPLAY_HELPER=TYPEC || TYPEC=y

If it is a select'able option, it doesn't make sense to use "depends"
here. Select will override depends.

> +       help
> +         DRM display helpers for USB Type-C Displayport Alternate mode.
> +
>  config DRM_DP_AUX_CHARDEV
>         bool "DRM DP AUX Interface"
>         depends on DRM && DRM_DISPLAY_HELPER
> diff --git a/drivers/gpu/drm/display/Makefile b/drivers/gpu/drm/display/Makefile
> index 17ac4a1006a8..2202a6aea38e 100644
> --- a/drivers/gpu/drm/display/Makefile
> +++ b/drivers/gpu/drm/display/Makefile
> @@ -8,6 +8,8 @@ drm_display_helper-$(CONFIG_DRM_DISPLAY_DP_HELPER) += \
>         drm_dp_helper.o \
>         drm_dp_mst_topology.o \
>         drm_dsc_helper.o
> +drm_display_helper-$(CONFIG_DRM_DISPLAY_DP_TYPEC_HELPER) += \
> +       drm_dp_typec_helper.o
>  drm_display_helper-$(CONFIG_DRM_DISPLAY_HDCP_HELPER) += drm_hdcp_helper.o
>  drm_display_helper-$(CONFIG_DRM_DISPLAY_HDMI_HELPER) += \
>         drm_hdmi_helper.o \
> diff --git a/drivers/gpu/drm/display/drm_dp_typec_helper.c b/drivers/gpu/drm/display/drm_dp_typec_helper.c
> new file mode 100644
> index 000000000000..1562a9ccdaf2
> --- /dev/null
> +++ b/drivers/gpu/drm/display/drm_dp_typec_helper.c
> @@ -0,0 +1,105 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/usb/typec_mux.h>
> +#include <drm/display/drm_dp_helper.h>
> +
> +static int drm_dp_register_mode_switch(struct device *dev,
> +                                      struct fwnode_handle *fwnode,
> +                                      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];

Why 32?

> +       u32 port_num;
> +       int ret;
> +
> +       ret = fwnode_property_read_u32(fwnode, "reg", &port_num);
> +       if (ret) {
> +               dev_err(dev, "Failed to read reg property: %d\n", ret);
> +               return ret;
> +       }
> +
> +       port_data = &switch_desc->typec_ports[port_num];
> +       port_data->data = data;
> +       port_data->port_num = port_num;
> +       port_data->fwnode = fwnode;
> +       mux_desc.fwnode = fwnode;
> +       mux_desc.drvdata = port_data;
> +       snprintf(name, sizeof(name), "%pfwP-%u", fwnode, port_num);

I think it makes more sense to use dev_name here instead of fwnode.

> +       mux_desc.name = name;
> +       mux_desc.set = mux_set;
> +
> +       port_data->typec_mux = typec_mux_register(dev, &mux_desc);
> +       ret = PTR_ERR_OR_ZERO(port_data->typec_mux);
> +       if (ret)
> +               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. This function uses devm_kcalloc
> + * to allocate memory, so it is expected to only call this in the driver probe
> + * functions.
> + *
> + * Currently only mode switches are implemented, and the function assumes the
> + * given @port device node has endpoints with "mode-switch" property.
> + * The port number is determined by the "reg" property of the endpoint.
> + */
> +int drm_dp_register_typec_switches(struct device *dev, struct fwnode_handle *port,
> +                                  struct drm_dp_typec_switch_desc *switch_desc,
> +                                  void *data, typec_mux_set_fn_t mux_set)
> +{
> +       struct fwnode_handle *sw;
> +       int ret;
> +
> +       switch_desc->num_typec_switches = typec_mode_switch_node_count(port);
> +       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_typec_mode_switch_node(port, sw) {
> +               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:
> +       fwnode_handle_put(sw);
> +       drm_dp_unregister_typec_switches(switch_desc);
> +       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)
> +{
> +       unsigned 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);
> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> index ab55453f2d2c..0fe56586d7bc 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 +764,49 @@ 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;
> +       int port_num;
> +       struct fwnode_handle *fwnode;
> +       void *data;
> +};
> +
> +struct drm_dp_typec_switch_desc {
> +       int num_typec_switches;
> +       struct drm_dp_typec_port_data *typec_ports;
> +};
> +
> +#define for_each_typec_mode_switch_node(port, sw)      \
> +       fwnode_for_each_child_node((port), (sw))        \
> +               for_each_if(fwnode_property_present((sw), "mode-switch"))
> +
> +static inline unsigned int typec_mode_switch_node_count(struct fwnode_handle *port)
> +{
> +       struct fwnode_handle *sw;
> +       unsigned int count = 0;
> +
> +       for_each_typec_mode_switch_node(port, sw)
> +               count++;
> +
> +       return count;
> +}
> +
> +#ifdef CONFIG_DRM_DISPLAY_DP_TYPEC_HELPER
> +void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc);
> +int drm_dp_register_typec_switches(struct device *dev, struct fwnode_handle *port,
> +                                  struct drm_dp_typec_switch_desc *switch_desc,
> +                                  void *data, typec_mux_set_fn_t mux_set);
> +#else
> +static inline void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc)
> +{
> +}
> +static inline int drm_dp_register_typec_switches(
> +               struct device *dev, struct fwnode_handle *port,
> +               struct drm_dp_typec_switch_desc *switch_desc, void *data,
> +               typec_mux_set_fn_t mux_set)
> +{
> +       return -EOPNOTSUPP;
> +}
> +#endif
> +
>  #endif /* _DRM_DP_HELPER_H_ */
> --
> 2.40.0.rc1.284.g88254d51c5-goog
>


-- 
With best wishes
Dmitry