[PATCHv2 1/3] drm: add support for DisplayPort CEC-Tunneling-over-AUX
Hans Verkuil
hverkuil at xs4all.nl
Sat Aug 12 09:01:05 UTC 2017
From: Hans Verkuil <hans.verkuil at 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 at cisco.com>
---
drivers/gpu/drm/Kconfig | 10 ++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_dp_cec.c | 302 +++++++++++++++++++++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 24 ++++
4 files changed, 337 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 24a066e1841c..c6552c62049e 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -40,6 +40,7 @@ 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..7f669900f5c1
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_cec.c
@@ -0,0 +1,302 @@
+/*
+ * 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), 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 at xs4all.nl) if you find an adapter that works
+ * and is not yet listed there.
+ */
+
+/**
+ * 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);
+ u8 buf[DP_AUX_MAX_PAYLOAD_BYTES];
+ u8 hw_rev;
+
+ if (drm_dp_dpcd_read(aux, DP_BRANCH_OUI,
+ buf, sizeof(buf)) != sizeof(buf))
+ return;
+ hw_rev = buf[9];
+ buf[9] = 0;
+ seq_printf(file, "OUI: %02x-%02x-%02x\n",
+ buf[0], buf[1], buf[2]);
+ seq_printf(file, "ID: %s\n", buf + 3);
+ seq_printf(file, "HW Rev: %d.%d\n", hw_rev >> 4, 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",
+ buf[10], buf[11], buf[10], buf[11]);
+}
+
+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 int drm_dp_cec_handle_irq(struct drm_dp_aux *aux)
+{
+ struct cec_adapter *adap = aux->cec_adap;
+ u8 flags;
+ ssize_t err;
+
+ err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, &flags);
+ if (err < 0)
+ return err;
+
+ 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 0;
+}
+
+/**
+ * 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 = false;
+ int attempts;
+
+ if (!aux->cec_adap)
+ return false;
+
+ for (attempts = 0; attempts < 4; attempts++) {
+ u8 cec_irq;
+ int ret;
+
+ ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,
+ &cec_irq);
+ if (ret < 0 || !(cec_irq & DP_CEC_IRQ))
+ break;
+
+ if (!drm_dp_cec_handle_irq(aux))
+ handled = true;
+
+ ret = drm_dp_dpcd_writeb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,
+ DP_CEC_IRQ);
+ if (ret < 0)
+ break;
+ }
+ 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 device
+ * @parent: parent device
+ *
+ * Checks if this is a DisplayPort-to-HDMI adapter that supports
+ * CEC-tunneling-over-AUX, and if so it creates a CEC device.
+ *
+ * If a CEC device was already created, then check if the capabilities
+ * have changed. If not, then do nothing. Otherwise destroy the old
+ * CEC device and create a new CEC device.
+ *
+ * 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)
+{
+ u32 cec_caps = CEC_CAP_LOG_ADDRS | CEC_CAP_TRANSMIT |
+ CEC_CAP_PASSTHROUGH | CEC_CAP_RC | 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 (!IS_ERR_OR_NULL(aux->cec_adap)) {
+ if (aux->cec_adap->capabilities == cec_caps &&
+ aux->cec_adap->available_log_addrs == num_las)
+ 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;
+ }
+ 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..0e236dd40b42 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -952,6 +952,8 @@ struct drm_dp_aux_msg {
size_t size;
};
+struct cec_adapter;
+
/**
* struct drm_dp_aux - DisplayPort AUX channel
* @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
@@ -1010,6 +1012,10 @@ 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 +1138,22 @@ 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);
+#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)
+{
+ return -ENODEV;
+}
+#endif
+
#endif /* _DRM_DP_HELPER_H_ */
--
2.13.2
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