Re: [PATCH v6 4/6] drm/bridge: implement generic DP HPD bridge

[Neil Armstrong <neil.armstrong@linaro.org>]

On 04/11/2023 00:03, Dmitry Baryshkov wrote:
> Several USB-C controllers implement a pretty simple DRM bridge which
> implements just the HPD notification operations. Add special helper
> for creating such simple bridges.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>   drivers/gpu/drm/bridge/Kconfig          |   8 ++
>   drivers/gpu/drm/bridge/Makefile         |   1 +
>   drivers/gpu/drm/bridge/aux-hpd-bridge.c | 164 ++++++++++++++++++++++++
>   include/drm/bridge/aux-bridge.h         |  18 +++
>   4 files changed, 191 insertions(+)
>   create mode 100644 drivers/gpu/drm/bridge/aux-hpd-bridge.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index f12eab62799f..19d2dc05c397 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -21,6 +21,14 @@ config DRM_AUX_BRIDGE
>   	  Simple transparent bridge that is used by several non-DRM drivers to
>   	  build bridges chain.
>   
> +config DRM_AUX_HPD_BRIDGE
> +	tristate
> +	depends on DRM_BRIDGE && OF
> +	select AUXILIARY_BUS
> +	help
> +	  Simple bridge that terminates the bridge chain and provides HPD
> +	  support.
> +
>   menu "Display Interface Bridges"
>   	depends on DRM && DRM_BRIDGE
>   
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 918e3bfff079..017b5832733b 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -1,5 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0
>   obj-$(CONFIG_DRM_AUX_BRIDGE) += aux-bridge.o
> +obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += aux-hpd-bridge.o
>   obj-$(CONFIG_DRM_CHIPONE_ICN6211) += chipone-icn6211.o
>   obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
>   obj-$(CONFIG_DRM_CROS_EC_ANX7688) += cros-ec-anx7688.o
> diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
> new file mode 100644
> index 000000000000..4defac8ec63f
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
> @@ -0,0 +1,164 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2023 Linaro Ltd.
> + *
> + * Author: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> + */
> +#include <linux/auxiliary_bus.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +
> +#include <drm/drm_bridge.h>
> +#include <drm/bridge/aux-bridge.h>
> +
> +static DEFINE_IDA(drm_aux_hpd_bridge_ida);
> +
> +struct drm_aux_hpd_bridge_data {
> +	struct drm_bridge bridge;
> +	struct device *dev;
> +};
> +
> +static void drm_aux_hpd_bridge_release(struct device *dev)
> +{
> +	struct auxiliary_device *adev = to_auxiliary_dev(dev);
> +
> +	ida_free(&drm_aux_hpd_bridge_ida, adev->id);
> +
> +	of_node_put(adev->dev.platform_data);
> +
> +	kfree(adev);
> +}
> +
> +static void drm_aux_hpd_bridge_unregister_adev(void *_adev)
> +{
> +	struct auxiliary_device *adev = _adev;
> +
> +	auxiliary_device_delete(adev);
> +	auxiliary_device_uninit(adev);
> +}
> +
> +/**
> + * drm_dp_hpd_bridge_register - Create a simple HPD DisplayPort bridge
> + * @parent: device instance providing this bridge
> + * @np: device node pointer corresponding to this bridge instance
> + *
> + * Creates a simple DRM bridge with the type set to
> + * DRM_MODE_CONNECTOR_DisplayPort, which terminates the bridge chain and is
> + * able to send the HPD events.
> + *
> + * Return: device instance that will handle created bridge or an error code
> + * encoded into the pointer.
> + */
> +struct device *drm_dp_hpd_bridge_register(struct device *parent,
> +					  struct device_node *np)
> +{
> +	struct auxiliary_device *adev;
> +	int ret;
> +
> +	adev = kzalloc(sizeof(*adev), GFP_KERNEL);
> +	if (!adev)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = ida_alloc(&drm_aux_hpd_bridge_ida, GFP_KERNEL);
> +	if (ret < 0) {
> +		kfree(adev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	adev->id = ret;
> +	adev->name = "dp_hpd_bridge";
> +	adev->dev.parent = parent;
> +	adev->dev.of_node = parent->of_node;
> +	adev->dev.release = drm_aux_hpd_bridge_release;
> +	adev->dev.platform_data = np;
> +
> +	ret = auxiliary_device_init(adev);
> +	if (ret) {
> +		ida_free(&drm_aux_hpd_bridge_ida, adev->id);
> +		kfree(adev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	ret = auxiliary_device_add(adev);
> +	if (ret) {
> +		auxiliary_device_uninit(adev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	ret = devm_add_action_or_reset(parent, drm_aux_hpd_bridge_unregister_adev, adev);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return &adev->dev;
> +
> +}
> +EXPORT_SYMBOL_GPL(drm_dp_hpd_bridge_register);
> +
> +/**
> + * drm_aux_hpd_bridge_notify - notify hot plug detection events
> + * @dev: device created for the HPD bridge
> + * @status: output connection status
> + *
> + * A wrapper around drm_bridge_hpd_notify() that is used to report hot plug
> + * detection events for bridges created via drm_dp_hpd_bridge_register().
> + *
> + * This function shall be called in a context that can sleep.
> + */
> +void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
> +{
> +	struct auxiliary_device *adev = to_auxiliary_dev(dev);
> +	struct drm_aux_hpd_bridge_data *data = auxiliary_get_drvdata(adev);
> +
> +	if (!data)
> +		return;
> +
> +	drm_bridge_hpd_notify(&data->bridge, status);
> +}
> +EXPORT_SYMBOL_GPL(drm_aux_hpd_bridge_notify);
> +
> +static int drm_aux_hpd_bridge_attach(struct drm_bridge *bridge,
> +				    enum drm_bridge_attach_flags flags)
> +{
> +	return flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR ? 0 : -EINVAL;
> +}
> +
> +static const struct drm_bridge_funcs drm_aux_hpd_bridge_funcs = {
> +	.attach	= drm_aux_hpd_bridge_attach,
> +};
> +
> +static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
> +				   const struct auxiliary_device_id *id)
> +{
> +	struct drm_aux_hpd_bridge_data *data;
> +
> +	data = devm_kzalloc(&auxdev->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->dev = &auxdev->dev;
> +	data->bridge.funcs = &drm_aux_hpd_bridge_funcs;
> +	data->bridge.of_node = dev_get_platdata(data->dev);
> +	data->bridge.ops = DRM_BRIDGE_OP_HPD;
> +	data->bridge.type = id->driver_data;
> +
> +	auxiliary_set_drvdata(auxdev, data);
> +
> +	return devm_drm_bridge_add(data->dev, &data->bridge);
> +}
> +
> +static const struct auxiliary_device_id drm_aux_hpd_bridge_table[] = {
> +	{ .name = KBUILD_MODNAME ".dp_hpd_bridge", .driver_data = DRM_MODE_CONNECTOR_DisplayPort, },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(auxiliary, drm_aux_hpd_bridge_table);
> +
> +static struct auxiliary_driver drm_aux_hpd_bridge_drv = {
> +	.name = "aux_hpd_bridge",
> +	.id_table = drm_aux_hpd_bridge_table,
> +	.probe = drm_aux_hpd_bridge_probe,
> +};
> +module_auxiliary_driver(drm_aux_hpd_bridge_drv);
> +
> +MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov@linaro.org>");
> +MODULE_DESCRIPTION("DRM HPD bridge");
> +MODULE_LICENSE("GPL");
> diff --git a/include/drm/bridge/aux-bridge.h b/include/drm/bridge/aux-bridge.h
> index 441ab3f0e920..33adaf4e4daa 100644
> --- a/include/drm/bridge/aux-bridge.h
> +++ b/include/drm/bridge/aux-bridge.h
> @@ -7,6 +7,8 @@
>   #ifndef DRM_AUX_BRIDGE_H
>   #define DRM_AUX_BRIDGE_H
>   
> +#include <drm/drm_connector.h>
> +
>   #if IS_ENABLED(CONFIG_DRM_AUX_BRIDGE)
>   int drm_aux_bridge_register(struct device *parent);
>   #else
> @@ -16,4 +18,20 @@ static inline int drm_aux_bridge_register(struct device *parent)
>   }
>   #endif
>   
> +#if IS_ENABLED(CONFIG_DRM_AUX_HPD_BRIDGE)
> +struct device *drm_dp_hpd_bridge_register(struct device *parent,
> +					  struct device_node *np);
> +void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status);
> +#else
> +static inline struct device *drm_dp_hpd_bridge_register(struct device *parent,
> +							struct device_node *np)
> +{
> +	return 0;
> +}
> +
> +static inline void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
> +{
> +}
> +#endif
> +
>   #endif

LGTM:
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>