// 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. Note that MegaChips 2900-based adapters appear to have good
* support for CEC tunneling. Those adapters that I have tested using
* this chipset all have the CEC line connected.
*
* 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: %*phD\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;
/* No transfer function was set, so not a DP connector */
if (!aux->transfer)
return;
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;
/* No transfer function was set, so not a DP connector */
if (!aux->transfer)
return;
#ifndef [31mCONFIG_MEDIA_CEC_RC[0m
/*
* 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)
{
/* No transfer function was set, so not a DP connector */
if (!aux->transfer)
return;
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);
if (WARN_ON(!aux->transfer))
return;
aux->cec.name = name;
aux->cec.parent = parent;
INIT_DELAYED_WORK(&aux->cec.unregister_work,
drm_dp_cec_unregister_work);
}
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);