drm: add support for DisplayPort CEC-Tunneling-over-AUX

	  default case is N. Details and instructions how to build your own

	  EDID data are given in Documentation/EDID/HOWTO.txt.

config DRM_DP_CEC

	bool "Enable DisplayPort CEC-Tunneling-over-AUX HDMI support"

	select CEC_CORE

	help

	  Choose this option if you want to enable HDMI CEC support for

	  DisplayPort/USB-C to HDMI adapters.

	  Note: not all adapters support this feature, and even for those

	  that do support this they often do not hook up the CEC pin.

config DRM_TTM

	tristate

	depends on DRM && MMU

drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o

drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o

drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o

drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o

obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o

obj-$(CONFIG_DRM_DEBUG_SELFTEST) += selftests/

// SPDX-License-Identifier: GPL-2.0

/*

 * DisplayPort CEC-Tunneling-over-AUX support

 *

 * Copyright 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved.

 */

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/slab.h>

#include <drm/drm_dp_helper.h>

#include <media/cec.h>

/*

 * Unfortunately it turns out that we have a chicken-and-egg situation

 * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters

 * have a converter chip that supports CEC-Tunneling-over-AUX (usually the

 * Parade PS176), but they do not wire up the CEC pin, thus making CEC

 * useless.

 *

 * Sadly there is no way for this driver to know this. What happens is

 * that a /dev/cecX device is created that is isolated and unable to see

 * any of the other CEC devices. Quite literally the CEC wire is cut

 * (or in this case, never connected in the first place).

 *

 * The reason so few adapters support this is that this tunneling protocol

 * was never supported by any OS. So there was no easy way of testing it,

 * and no incentive to correctly wire up the CEC pin.

 *

 * Hopefully by creating this driver it will be easier for vendors to

 * finally fix their adapters and test the CEC functionality.

 *

 * I keep a list of known working adapters here:

 *

 * https://hverkuil.home.xs4all.nl/cec-status.txt

 *

 * Please mail me (hverkuil@xs4all.nl) if you find an adapter that works

 * and is not yet listed there.

 *

 * Note that the current implementation does not support CEC over an MST hub.

 * As far as I can see there is no mechanism defined in the DisplayPort

 * standard to transport CEC interrupts over an MST device. It might be

 * possible to do this through polling, but I have not been able to get that

 * to work.

 */

/**

 * DOC: dp cec helpers

 *

 * These functions take care of supporting the CEC-Tunneling-over-AUX

 * feature of DisplayPort-to-HDMI adapters.

 */

/*

 * When the EDID is unset because the HPD went low, then the CEC DPCD registers

 * typically can no longer be read (true for a DP-to-HDMI adapter since it is

 * powered by the HPD). However, some displays toggle the HPD off and on for a

 * short period for one reason or another, and that would cause the CEC adapter

 * to be removed and added again, even though nothing else changed.

 *

 * This module parameter sets a delay in seconds before the CEC adapter is

 * actually unregistered. Only if the HPD does not return within that time will

 * the CEC adapter be unregistered.

 *

 * If it is set to a value >= NEVER_UNREG_DELAY, then the CEC adapter will never

 * be unregistered for as long as the connector remains registered.

 *

 * If it is set to 0, then the CEC adapter will be unregistered immediately as

 * soon as the HPD disappears.

 *

 * The default is one second to prevent short HPD glitches from unregistering

 * the CEC adapter.

 *

 * Note that for integrated HDMI branch devices that support CEC the DPCD

 * registers remain available even if the HPD goes low since it is not powered

 * by the HPD. In that case the CEC adapter will never be unregistered during

 * the life time of the connector. At least, this is the theory since I do not

 * have hardware with an integrated HDMI branch device that supports CEC.

 */

#define NEVER_UNREG_DELAY 1000

static unsigned int drm_dp_cec_unregister_delay = 1;

module_param(drm_dp_cec_unregister_delay, uint, 0600);

MODULE_PARM_DESC(drm_dp_cec_unregister_delay,

		 "CEC unregister delay in seconds, 0: no delay, >= 1000: never unregister");

static int drm_dp_cec_adap_enable(struct cec_adapter *adap, bool enable)

{

	struct drm_dp_aux *aux = cec_get_drvdata(adap);

	u32 val = enable ? DP_CEC_TUNNELING_ENABLE : 0;

	ssize_t err = 0;

	err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val);

	return (enable && err < 0) ? err : 0;

}

static int drm_dp_cec_adap_log_addr(struct cec_adapter *adap, u8 addr)

{

	struct drm_dp_aux *aux = cec_get_drvdata(adap);

	/* Bit 15 (logical address 15) should always be set */

	u16 la_mask = 1 << CEC_LOG_ADDR_BROADCAST;

	u8 mask[2];

	ssize_t err;

	if (addr != CEC_LOG_ADDR_INVALID)

		la_mask |= adap->log_addrs.log_addr_mask | (1 << addr);

	mask[0] = la_mask & 0xff;

	mask[1] = la_mask >> 8;

	err = drm_dp_dpcd_write(aux, DP_CEC_LOGICAL_ADDRESS_MASK, mask, 2);

	return (addr != CEC_LOG_ADDR_INVALID && err < 0) ? err : 0;

}

static int drm_dp_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,

				    u32 signal_free_time, struct cec_msg *msg)

{

	struct drm_dp_aux *aux = cec_get_drvdata(adap);

	unsigned int retries = min(5, attempts - 1);

	ssize_t err;

	err = drm_dp_dpcd_write(aux, DP_CEC_TX_MESSAGE_BUFFER,

				msg->msg, msg->len);

	if (err < 0)

		return err;

	err = drm_dp_dpcd_writeb(aux, DP_CEC_TX_MESSAGE_INFO,

				 (msg->len - 1) | (retries << 4) |

				 DP_CEC_TX_MESSAGE_SEND);

	return err < 0 ? err : 0;

}

static int drm_dp_cec_adap_monitor_all_enable(struct cec_adapter *adap,

					      bool enable)

{

	struct drm_dp_aux *aux = cec_get_drvdata(adap);

	ssize_t err;

	u8 val;

	if (!(adap->capabilities & CEC_CAP_MONITOR_ALL))

		return 0;

	err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CONTROL, &val);

	if (err >= 0) {

		if (enable)

			val |= DP_CEC_SNOOPING_ENABLE;

		else

			val &= ~DP_CEC_SNOOPING_ENABLE;

		err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val);

	}

	return (enable && err < 0) ? err : 0;

}

static void drm_dp_cec_adap_status(struct cec_adapter *adap,

				   struct seq_file *file)

{

	struct drm_dp_aux *aux = cec_get_drvdata(adap);

	struct drm_dp_desc desc;

	struct drm_dp_dpcd_ident *id = &desc.ident;

	if (drm_dp_read_desc(aux, &desc, true))

		return;

	seq_printf(file, "OUI: %*pdH\n",

		   (int)sizeof(id->oui), id->oui);

	seq_printf(file, "ID: %*pE\n",

		   (int)strnlen(id->device_id, sizeof(id->device_id)),

		   id->device_id);

	seq_printf(file, "HW Rev: %d.%d\n", id->hw_rev >> 4, id->hw_rev & 0xf);

	/*

	 * Show this both in decimal and hex: at least one vendor

	 * always reports this in hex.

	 */

	seq_printf(file, "FW/SW Rev: %d.%d (0x%02x.0x%02x)\n",

		   id->sw_major_rev, id->sw_minor_rev,

		   id->sw_major_rev, id->sw_minor_rev);

}

static const struct cec_adap_ops drm_dp_cec_adap_ops = {

	.adap_enable = drm_dp_cec_adap_enable,

	.adap_log_addr = drm_dp_cec_adap_log_addr,

	.adap_transmit = drm_dp_cec_adap_transmit,

	.adap_monitor_all_enable = drm_dp_cec_adap_monitor_all_enable,

	.adap_status = drm_dp_cec_adap_status,

};

static int drm_dp_cec_received(struct drm_dp_aux *aux)

{

	struct cec_adapter *adap = aux->cec.adap;

	struct cec_msg msg;

	u8 rx_msg_info;

	ssize_t err;

	err = drm_dp_dpcd_readb(aux, DP_CEC_RX_MESSAGE_INFO, &rx_msg_info);

	if (err < 0)

		return err;

	if (!(rx_msg_info & DP_CEC_RX_MESSAGE_ENDED))

		return 0;

	msg.len = (rx_msg_info & DP_CEC_RX_MESSAGE_LEN_MASK) + 1;

	err = drm_dp_dpcd_read(aux, DP_CEC_RX_MESSAGE_BUFFER, msg.msg, msg.len);

	if (err < 0)

		return err;

	cec_received_msg(adap, &msg);

	return 0;

}

static void drm_dp_cec_handle_irq(struct drm_dp_aux *aux)

{

	struct cec_adapter *adap = aux->cec.adap;

	u8 flags;

	if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, &flags) < 0)

		return;

	if (flags & DP_CEC_RX_MESSAGE_INFO_VALID)

		drm_dp_cec_received(aux);

	if (flags & DP_CEC_TX_MESSAGE_SENT)

		cec_transmit_attempt_done(adap, CEC_TX_STATUS_OK);

	else if (flags & DP_CEC_TX_LINE_ERROR)

		cec_transmit_attempt_done(adap, CEC_TX_STATUS_ERROR |

						CEC_TX_STATUS_MAX_RETRIES);

	else if (flags &

		 (DP_CEC_TX_ADDRESS_NACK_ERROR | DP_CEC_TX_DATA_NACK_ERROR))

		cec_transmit_attempt_done(adap, CEC_TX_STATUS_NACK |

						CEC_TX_STATUS_MAX_RETRIES);

	drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, flags);

}

/**

 * drm_dp_cec_irq() - handle CEC interrupt, if any

 * @aux: DisplayPort AUX channel

 *

 * Should be called when handling an IRQ_HPD request. If CEC-tunneling-over-AUX

 * is present, then it will check for a CEC_IRQ and handle it accordingly.

 */

void drm_dp_cec_irq(struct drm_dp_aux *aux)

{

	u8 cec_irq;

	int ret;

	mutex_lock(&aux->cec.lock);

	if (!aux->cec.adap)

		goto unlock;

	ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,

				&cec_irq);

	if (ret < 0 || !(cec_irq & DP_CEC_IRQ))

		goto unlock;

	drm_dp_cec_handle_irq(aux);

	drm_dp_dpcd_writeb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, DP_CEC_IRQ);

unlock:

	mutex_unlock(&aux->cec.lock);

}

EXPORT_SYMBOL(drm_dp_cec_irq);

static bool drm_dp_cec_cap(struct drm_dp_aux *aux, u8 *cec_cap)

{

	u8 cap = 0;

	if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CAPABILITY, &cap) != 1 ||

	    !(cap & DP_CEC_TUNNELING_CAPABLE))

		return false;

	if (cec_cap)

		*cec_cap = cap;

	return true;

}

/*

 * Called if the HPD was low for more than drm_dp_cec_unregister_delay

 * seconds. This unregisters the CEC adapter.

 */

static void drm_dp_cec_unregister_work(struct work_struct *work)

{

	struct drm_dp_aux *aux = container_of(work, struct drm_dp_aux,

					      cec.unregister_work.work);

	mutex_lock(&aux->cec.lock);

	cec_unregister_adapter(aux->cec.adap);

	aux->cec.adap = NULL;

	mutex_unlock(&aux->cec.lock);

}

/*

 * A new EDID is set. If there is no CEC adapter, then create one. If

 * there was a CEC adapter, then check if the CEC adapter properties

 * were unchanged and just update the CEC physical address. Otherwise

 * unregister the old CEC adapter and create a new one.

 */

void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid)

{

	u32 cec_caps = CEC_CAP_DEFAULTS | CEC_CAP_NEEDS_HPD;

	unsigned int num_las = 1;

	u8 cap;

#ifndef CONFIG_MEDIA_CEC_RC

	/*

	 * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by

	 * cec_allocate_adapter() if CONFIG_MEDIA_CEC_RC is undefined.

	 *

	 * Do this here as well to ensure the tests against cec_caps are

	 * correct.

	 */

	cec_caps &= ~CEC_CAP_RC;

#endif

	cancel_delayed_work_sync(&aux->cec.unregister_work);

	mutex_lock(&aux->cec.lock);

	if (!drm_dp_cec_cap(aux, &cap)) {

		/* CEC is not supported, unregister any existing adapter */

		cec_unregister_adapter(aux->cec.adap);

		aux->cec.adap = NULL;

		goto unlock;

	}

	if (cap & DP_CEC_SNOOPING_CAPABLE)

		cec_caps |= CEC_CAP_MONITOR_ALL;

	if (cap & DP_CEC_MULTIPLE_LA_CAPABLE)

		num_las = CEC_MAX_LOG_ADDRS;

	if (aux->cec.adap) {

		if (aux->cec.adap->capabilities == cec_caps &&

		    aux->cec.adap->available_log_addrs == num_las) {

			/* Unchanged, so just set the phys addr */

			cec_s_phys_addr_from_edid(aux->cec.adap, edid);

			goto unlock;

		}

		/*

		 * The capabilities changed, so unregister the old

		 * adapter first.

		 */

		cec_unregister_adapter(aux->cec.adap);

	}

	/* Create a new adapter */

	aux->cec.adap = cec_allocate_adapter(&drm_dp_cec_adap_ops,

					     aux, aux->cec.name, cec_caps,

					     num_las);

	if (IS_ERR(aux->cec.adap)) {

		aux->cec.adap = NULL;

		goto unlock;

	}

	if (cec_register_adapter(aux->cec.adap, aux->cec.parent)) {

		cec_delete_adapter(aux->cec.adap);

		aux->cec.adap = NULL;

	} else {

		/*

		 * Update the phys addr for the new CEC adapter. When called

		 * from drm_dp_cec_register_connector() edid == NULL, so in

		 * that case the phys addr is just invalidated.

		 */

		cec_s_phys_addr_from_edid(aux->cec.adap, edid);

	}

unlock:

	mutex_unlock(&aux->cec.lock);

}

EXPORT_SYMBOL(drm_dp_cec_set_edid);

/*

 * The EDID disappeared (likely because of the HPD going down).

 */

void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)

{

	cancel_delayed_work_sync(&aux->cec.unregister_work);

	mutex_lock(&aux->cec.lock);

	if (!aux->cec.adap)

		goto unlock;

	cec_phys_addr_invalidate(aux->cec.adap);

	/*

	 * We're done if we want to keep the CEC device

	 * (drm_dp_cec_unregister_delay is >= NEVER_UNREG_DELAY) or if the

	 * DPCD still indicates the CEC capability (expected for an integrated

	 * HDMI branch device).

	 */

	if (drm_dp_cec_unregister_delay < NEVER_UNREG_DELAY &&

	    !drm_dp_cec_cap(aux, NULL)) {

		/*

		 * Unregister the CEC adapter after drm_dp_cec_unregister_delay

		 * seconds. This to debounce short HPD off-and-on cycles from

		 * displays.

		 */

		schedule_delayed_work(&aux->cec.unregister_work,

				      drm_dp_cec_unregister_delay * HZ);

	}

unlock:

	mutex_unlock(&aux->cec.lock);

}

EXPORT_SYMBOL(drm_dp_cec_unset_edid);

/**

 * drm_dp_cec_register_connector() - register a new connector

 * @aux: DisplayPort AUX channel

 * @name: name of the CEC device

 * @parent: parent device

 *

 * A new connector was registered with associated CEC adapter name and

 * CEC adapter parent device. After registering the name and parent

 * drm_dp_cec_set_edid() is called to check if the connector supports

 * CEC and to register a CEC adapter if that is the case.

 */

void drm_dp_cec_register_connector(struct drm_dp_aux *aux, const char *name,

				   struct device *parent)

{

	WARN_ON(aux->cec.adap);

	aux->cec.name = name;

	aux->cec.parent = parent;

	INIT_DELAYED_WORK(&aux->cec.unregister_work,

			  drm_dp_cec_unregister_work);

	drm_dp_cec_set_edid(aux, NULL);

}

EXPORT_SYMBOL(drm_dp_cec_register_connector);

/**

 * drm_dp_cec_unregister_connector() - unregister the CEC adapter, if any

 * @aux: DisplayPort AUX channel

 */

void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux)

{

	if (!aux->cec.adap)

		return;

	cancel_delayed_work_sync(&aux->cec.unregister_work);

	cec_unregister_adapter(aux->cec.adap);

	aux->cec.adap = NULL;

}

EXPORT_SYMBOL(drm_dp_cec_unregister_connector);

void drm_dp_aux_init(struct drm_dp_aux *aux)

{

	mutex_init(&aux->hw_mutex);

	mutex_init(&aux->cec.lock);

	INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work);

	aux->ddc.algo = &drm_dp_i2c_algo;

	size_t size;

};

struct cec_adapter;

struct edid;

/**

 * struct drm_dp_aux_cec - DisplayPort CEC-Tunneling-over-AUX

 * @lock: mutex protecting this struct

 * @adap: the CEC adapter for CEC-Tunneling-over-AUX support.

 * @name: name of the CEC adapter

 * @parent: parent device of the CEC adapter

 * @unregister_work: unregister the CEC adapter

 */

struct drm_dp_aux_cec {

	struct mutex lock;

	struct cec_adapter *adap;

	const char *name;

	struct device *parent;

	struct delayed_work unregister_work;

};

/**

 * struct drm_dp_aux - DisplayPort AUX channel

 * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter

	 * @i2c_defer_count: Counts I2C DEFERs, used for DP validation.

	 */

	unsigned i2c_defer_count;

	/**

	 * @cec: struct containing fields used for CEC-Tunneling-over-AUX.

	 */

	struct drm_dp_aux_cec cec;

};

ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,

	return desc->quirks & BIT(quirk);

}

#ifdef CONFIG_DRM_DP_CEC

void drm_dp_cec_irq(struct drm_dp_aux *aux);

void drm_dp_cec_register_connector(struct drm_dp_aux *aux, const char *name,

				   struct device *parent);

void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux);

void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid);

void drm_dp_cec_unset_edid(struct drm_dp_aux *aux);

#else

static inline void drm_dp_cec_irq(struct drm_dp_aux *aux)

{

}

static inline void drm_dp_cec_register_connector(struct drm_dp_aux *aux,

						 const char *name,

						 struct device *parent)

{

}

static inline void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux)

{

}

static inline void drm_dp_cec_set_edid(struct drm_dp_aux *aux,

				       const struct edid *edid)

{

}

static inline void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)

{

}

#endif

#endif /* _DRM_DP_HELPER_H_ */