Commit 2c6d1fff authored by Hans Verkuil's avatar Hans Verkuil Committed by Ville Syrjälä

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

This adds support for the DisplayPort CEC-Tunneling-over-AUX
feature that is part of the DisplayPort 1.3 standard.

Unfortunately, not all DisplayPort/USB-C to HDMI adapters with a
chip that has this capability actually hook up the CEC pin, so
even though a CEC device is created, it may not actually work.
Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180711132909.25409-2-hverkuil@xs4all.nl
parent cf19fa2c
...@@ -122,6 +122,16 @@ config DRM_LOAD_EDID_FIRMWARE ...@@ -122,6 +122,16 @@ config DRM_LOAD_EDID_FIRMWARE
default case is N. Details and instructions how to build your own default case is N. Details and instructions how to build your own
EDID data are given in Documentation/EDID/HOWTO.txt. 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 config DRM_TTM
tristate tristate
depends on DRM && MMU depends on DRM && MMU
......
...@@ -41,6 +41,7 @@ drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o ...@@ -41,6 +41,7 @@ drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o drm_kms_helper-$(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_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_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-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
obj-$(CONFIG_DRM_DEBUG_SELFTEST) += selftests/ 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);
...@@ -1087,6 +1087,7 @@ static void drm_dp_aux_crc_work(struct work_struct *work) ...@@ -1087,6 +1087,7 @@ static void drm_dp_aux_crc_work(struct work_struct *work)
void drm_dp_aux_init(struct drm_dp_aux *aux) void drm_dp_aux_init(struct drm_dp_aux *aux)
{ {
mutex_init(&aux->hw_mutex); mutex_init(&aux->hw_mutex);
mutex_init(&aux->cec.lock);
INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work); INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work);
aux->ddc.algo = &drm_dp_i2c_algo; aux->ddc.algo = &drm_dp_i2c_algo;
......
...@@ -1078,6 +1078,25 @@ struct drm_dp_aux_msg { ...@@ -1078,6 +1078,25 @@ struct drm_dp_aux_msg {
size_t size; 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 * struct drm_dp_aux - DisplayPort AUX channel
* @name: user-visible name of this AUX channel and the I2C-over-AUX adapter * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
...@@ -1136,6 +1155,10 @@ struct drm_dp_aux { ...@@ -1136,6 +1155,10 @@ struct drm_dp_aux {
* @i2c_defer_count: Counts I2C DEFERs, used for DP validation. * @i2c_defer_count: Counts I2C DEFERs, used for DP validation.
*/ */
unsigned i2c_defer_count; 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, ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
...@@ -1258,4 +1281,37 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk quirk) ...@@ -1258,4 +1281,37 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk quirk)
return desc->quirks & BIT(quirk); 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_ */ #endif /* _DRM_DP_HELPER_H_ */
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