On Tue, Jun 12, 2018 at 01:18:29PM +0200, Hans Verkuil wrote: > From: Hans Verkuil <hans.verkuil@xxxxxxxxx> > > 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: Hans Verkuil <hans.verkuil@xxxxxxxxx> > --- > drivers/gpu/drm/Kconfig | 10 + > drivers/gpu/drm/Makefile | 1 + > drivers/gpu/drm/drm_dp_cec.c | 423 ++++++++++++++++++++++++++++++++ > drivers/gpu/drm/drm_dp_helper.c | 1 + > include/drm/drm_dp_helper.h | 56 +++++ > 5 files changed, 491 insertions(+) > create mode 100644 drivers/gpu/drm/drm_dp_cec.c > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > index deeefa7a1773..d63876425cdc 100644 > --- a/drivers/gpu/drm/Kconfig > +++ b/drivers/gpu/drm/Kconfig > @@ -121,6 +121,16 @@ 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 && MMU > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile > index 50093ff4479b..c787481c2502 100644 > --- a/drivers/gpu/drm/Makefile > +++ b/drivers/gpu/drm/Makefile > @@ -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-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o > drm_kms_helper-$(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_MM_SELFTEST) += selftests/ > diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c > new file mode 100644 > index 000000000000..555a9fca3fef > --- /dev/null > +++ b/drivers/gpu/drm/drm_dp_cec.c > @@ -0,0 +1,423 @@ > +// 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@xxxxxxxxx) 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. And whatever is trying to do cec is happy with the dpcd accesses failing during that time? > + * > + * If it is set to 0, then the CEC adapter will never be unregistered for as > + * long as the connector remains registered. > + * > + * 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. > + */ > +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 == 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) > +I think I looked at the dpcd detais last time around. { > + 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) 'msg' could be const perhaps? > +{ > + 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_mutex); > + 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_mutex); > +} > +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); > + > + if (!aux->cec_adap) > + return; > + mutex_lock(&aux->cec_mutex); > + cec_unregister_adapter(aux->cec_adap); > + aux->cec_adap = NULL; > + mutex_unlock(&aux->cec_mutex); > +} > + > +/* > + * 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, struct edid *edid) 'edid' can be const. > +{ > + 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_mutex); > + 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_mutex); > +} > +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) > +{ > + mutex_lock(&aux->cec_mutex); > + 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 0) or if the DPCD still indicates > + * the CEC capability (expected for an integrated HDMI branch device). > + */ > + if (!drm_dp_cec_unregister_delay || drm_dp_cec_cap(aux, NULL)) > + goto unlock; The drm_dp_cec_unregister_delay semantics seem a bit unnatural to me. I think ==0 -> no delay, <0 -> infinite delay would make more sense. Although we already have the exact opposite with the vblank_offdelay for some historical reason :( > + > + cancel_delayed_work_sync(&aux->cec_unregister_work); This looks like a potential deadlock to me. > + if (aux->cec_adap) { > + /* sanity check */ > + if (drm_dp_cec_unregister_delay > 600) > + drm_dp_cec_unregister_delay = 600; > + /* > + * 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_mutex); > +} > +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); > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c > index ffe14ec3e7f2..e6b0e08ee0aa 100644 > --- a/drivers/gpu/drm/drm_dp_helper.c > +++ b/drivers/gpu/drm/drm_dp_helper.c > @@ -1073,6 +1073,7 @@ static void drm_dp_aux_crc_work(struct work_struct *work) > void drm_dp_aux_init(struct drm_dp_aux *aux) > { > mutex_init(&aux->hw_mutex); > + mutex_init(&aux->cec_mutex); > INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work); > > aux->ddc.algo = &drm_dp_i2c_algo; > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h > index 62903bae0221..415ac52e8599 100644 > --- a/include/drm/drm_dp_helper.h > +++ b/include/drm/drm_dp_helper.h > @@ -1062,6 +1062,9 @@ struct drm_dp_aux_msg { > size_t size; > }; > > +struct cec_adapter; > +struct edid; > + > /** > * struct drm_dp_aux - DisplayPort AUX channel > * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter > @@ -1120,6 +1123,26 @@ struct drm_dp_aux { > * @i2c_defer_count: Counts I2C DEFERs, used for DP validation. > */ > unsigned i2c_defer_count; > + /** > + * @cec_mutex: mutex protecting the cec_ fields > + */ > + struct mutex cec_mutex; > + /** > + * @cec_adap: the CEC adapter for CEC-Tunneling-over-AUX support. > + */ > + struct cec_adapter *cec_adap; > + /** > + * @cec_name: name of the CEC adapter > + */ > + const char *cec_name; > + /** > + * @cec_parent: parent device of the CEC adapter > + */ > + struct device *cec_parent; > + /** > + * @cec_unregister_work: unregister the CEC adapter > + */ > + struct delayed_work cec_unregister_work; 'struct { ... } cec;' could be a decent idea here. I think I looked at the dpcd detais last time around so I'll not bother this time around with that. Apart from the possible deadlock I think this is looking pretty good. > }; > > ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, > @@ -1242,4 +1265,37 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk 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, 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, > + struct edid *edid) > +{ > +} > + > +static inline void drm_dp_cec_unset_edid(struct drm_dp_aux *aux) > +{ > +} > + > +#endif > + > #endif /* _DRM_DP_HELPER_H_ */ > -- > 2.17.0 -- Ville Syrjälä Intel
