From: Hans Verkuil hans.verkuil@cisco.com
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@cisco.com --- Changes since v4:
- Updated comment at the start of drm_dp_cec.c - Add edid pointer to drm_dp_cec_configure_adapter --- drivers/gpu/drm/Kconfig | 10 ++ drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_dp_cec.c | 304 +++++++++++++++++++++++++++++++++++++++++++ include/drm/drm_dp_helper.h | 27 ++++ 4 files changed, 342 insertions(+) create mode 100644 drivers/gpu/drm/drm_dp_cec.c
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 83cb2a88c204..1f2708df5c4e 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -120,6 +120,16 @@ 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 8ce07039bb89..6f0cd526703e 100644 --- a/drivers/gpu/drm/Makefile +++ b/drivers/gpu/drm/Makefile @@ -41,6 +41,7 @@ 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 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..e72051bfa18c --- /dev/null +++ b/drivers/gpu/drm/drm_dp_cec.c @@ -0,0 +1,304 @@ +/* + * DisplayPort CEC-Tunneling-over-AUX support + * + * Copyright 2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved. + * + * This program is free software; you may redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; version 2 of the License. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +#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 or MegaChips MCDP2900), 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). + * + * I suspect that 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. + */ + +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 bool 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 false; + + 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); + return true; +} + +/** + * 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. + * + * Returns true if an interrupt was handled successfully or false otherwise. + */ +bool drm_dp_cec_irq(struct drm_dp_aux *aux) +{ + bool handled; + u8 cec_irq; + int ret; + + if (!aux->cec_adap) + return false; + + ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, + &cec_irq); + if (ret < 0 || !(cec_irq & DP_CEC_IRQ)) + return false; + + handled = drm_dp_cec_handle_irq(aux); + drm_dp_dpcd_writeb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1, DP_CEC_IRQ); + return handled; +} +EXPORT_SYMBOL(drm_dp_cec_irq); + +/** + * drm_dp_cec_configure_adapter() - configure the CEC adapter + * @aux: DisplayPort AUX channel + * @name: name of the CEC adapter + * @parent: parent device + * @edid: initial EDID, may be NULL (== invalid physical address) + * + * Checks if this is a DisplayPort-to-HDMI adapter that supports + * CEC-tunneling-over-AUX, and if so it creates a CEC adapter. + * + * If a CEC adapter was already created, then check if the capabilities + * have changed. If not, then only update the EDID for the existing + * CEC adapter. Otherwise destroy the old CEC adapter (if any) and create + * a new CEC adapter and set the initial EDID for that adapter. + * + * This can happen when one DP-to-HDMI adapter is disconnected and + * replaced by another adapter with different CEC capabilities. + * + * Returns 0 on success or a negative error code on failure. + */ +int drm_dp_cec_configure_adapter(struct drm_dp_aux *aux, const char *name, + struct device *parent, const struct edid *edid) +{ + u32 cec_caps = CEC_CAP_DEFAULTS | CEC_CAP_NEEDS_HPD; + unsigned int num_las = 1; + int err; + u8 cap; + + if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CAPABILITY, &cap) != 1 || + !(cap & DP_CEC_TUNNELING_CAPABLE)) { + cec_unregister_adapter(aux->cec_adap); + aux->cec_adap = NULL; + return -ENODEV; + } + + 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) { + cec_s_phys_addr_from_edid(aux->cec_adap, edid); + return 0; + } + cec_unregister_adapter(aux->cec_adap); + } + + aux->cec_adap = cec_allocate_adapter(&drm_dp_cec_adap_ops, + aux, name, cec_caps, num_las); + if (IS_ERR(aux->cec_adap)) { + err = PTR_ERR(aux->cec_adap); + aux->cec_adap = NULL; + return err; + } + err = cec_register_adapter(aux->cec_adap, parent); + if (err) { + cec_delete_adapter(aux->cec_adap); + aux->cec_adap = NULL; + } + cec_s_phys_addr_from_edid(aux->cec_adap, edid); + return err; +} +EXPORT_SYMBOL(drm_dp_cec_configure_adapter); diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index b17476a6909c..9bac0c47f62b 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -952,6 +952,9 @@ 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 @@ -1010,6 +1013,10 @@ struct drm_dp_aux { * @i2c_defer_count: Counts I2C DEFERs, used for DP validation. */ unsigned i2c_defer_count; + /** + * @cec_adap: the CEC adapter for CEC-Tunneling-over-AUX support. + */ + struct cec_adapter *cec_adap; };
ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, @@ -1132,4 +1139,24 @@ 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 +bool drm_dp_cec_irq(struct drm_dp_aux *aux); +int drm_dp_cec_configure_adapter(struct drm_dp_aux *aux, const char *name, + struct device *parent, + const struct edid *edid); +#else +static inline bool drm_dp_cec_irq(struct drm_dp_aux *aux) +{ + return false; +} + +static inline int drm_dp_cec_configure_adapter(struct drm_dp_aux *aux, + const char *name, + struct device *parent, + const struct edid *edid) +{ + return -ENODEV; +} +#endif + #endif /* _DRM_DP_HELPER_H_ */