drm: add support for DisplayPort CEC-Tunneling-over-AUX (1d4cf026) · Commits · e / devices / android_kernel_fairphone_FP3

drivers/gpu/drm/Kconfig

+10 −0

Original line number	Diff line number	Diff line
		@@ -83,6 +83,16 @@ config DRM_LOAD_EDID_FIRMWARE
		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

drivers/gpu/drm/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -33,6 +33,7 @@ drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
		drm_kms_helper-$(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

drivers/gpu/drm/drm_dp_cec.c

0 → 100644

+428 −0

Original line number	Diff line number	Diff line
		// 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);

drivers/gpu/drm/drm_dp_helper.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -990,6 +990,7 @@ static const struct i2c_lock_operations drm_dp_i2c_lock_ops = {
		void drm_dp_aux_init(struct drm_dp_aux *aux)
		{
		mutex_init(&aux->hw_mutex);
		mutex_init(&aux->cec.lock);

		aux->ddc.algo = &drm_dp_i2c_algo;
		aux->ddc.algo_data = aux;

include/drm/drm_dp_helper.h

+56 −0

Original line number	Diff line number	Diff line
		@@ -794,6 +794,25 @@ struct drm_dp_aux_msg {
		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
		@@ -846,6 +865,10 @@ struct drm_dp_aux {
		* @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,
		@@ -914,4 +937,37 @@ void drm_dp_aux_init(struct drm_dp_aux *aux);
		int drm_dp_aux_register(struct drm_dp_aux *aux);
		void drm_dp_aux_unregister(struct drm_dp_aux *aux);

		#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_ */