[RFC PATCH 6/7] drm: add support for DisplayPort CEC-Tunneling-over-AUX

From: Hans Verkuil <hverkuil@xs4all.nl>
To: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	Clint Taylor <clinton.a.taylor@intel.com>,
	Jani Nikula <jani.nikula@intel.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Hans Verkuil <hans.verkuil@cisco.com>
Subject: [RFC PATCH 6/7] drm: add support for DisplayPort CEC-Tunneling-over-AUX
Date: Thu, 25 May 2017 17:06:25 +0200	[thread overview]
Message-ID: <20170525150626.29748-7-hverkuil@xs4all.nl> (raw)
In-Reply-To: <20170525150626.29748-1-hverkuil@xs4all.nl>

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>
---
 drivers/gpu/drm/Kconfig      |   3 +
 drivers/gpu/drm/Makefile     |   1 +
 drivers/gpu/drm/drm_dp_cec.c | 196 +++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h  |  24 ++++++
 4 files changed, 224 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_dp_cec.c

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 78d7fc0ebb57..dd771ce8a3d0 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -120,6 +120,9 @@ 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
+
 config DRM_TTM
 	tristate
 	depends on DRM && MMU
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 59f0f9b696eb..22f1a17dfc8a 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -34,6 +34,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
 		drm_simple_kms_helper.o drm_modeset_helper.o \
 		drm_scdc_helper.o
 
+drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
 drm_kms_helper-$(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
diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
new file mode 100644
index 000000000000..44c544ba53cb
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_cec.c
@@ -0,0 +1,196 @@
+/*
+ * 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>
+
+static int drm_dp_cec_adap_enable(struct cec_adapter *adap, bool enable)
+{
+	struct drm_dp_aux *aux = cec_get_drvdata(adap);
+	ssize_t err = 0;
+
+	if (enable)
+		err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL,
+					 DP_CEC_TUNNELING_ENABLE);
+	else
+		err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, 0);
+	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);
+	u8 mask[2] = { 0x00, 0x80 };
+	ssize_t err;
+
+	if (addr != CEC_LOG_ADDR_INVALID) {
+		u16 la_mask = adap->log_addrs.log_addr_mask;
+
+		la_mask |= 0x8000 | (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 = 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;
+
+	if (retries > 5)
+		retries = 5;
+	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 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,
+};
+
+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;
+}
+
+int drm_dp_cec_irq(struct drm_dp_aux *aux)
+{
+	struct cec_adapter *adap = aux->cec_adap;
+	u8 flags;
+	ssize_t err;
+
+	if (!aux->cec_adap)
+		return 0;
+
+	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_done(adap, CEC_TX_STATUS_OK, 0, 0, 0, 0);
+	else if (flags & DP_CEC_TX_LINE_ERROR)
+		cec_transmit_done(adap, CEC_TX_STATUS_ERROR |
+				  CEC_TX_STATUS_MAX_RETRIES, 0, 0, 0, 1);
+	else if (flags &
+		 (DP_CEC_TX_ADDRESS_NACK_ERROR | DP_CEC_TX_DATA_NACK_ERROR))
+		cec_transmit_done(adap, CEC_TX_STATUS_NACK |
+				  CEC_TX_STATUS_MAX_RETRIES, 0, 1, 0, 0);
+	drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, flags);
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_cec_irq);
+
+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 3f4ad709534e..1e373df48108 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -843,6 +843,8 @@ 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
@@ -901,6 +903,10 @@ 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,
@@ -972,4 +978,22 @@ void drm_dp_aux_unregister(struct drm_dp_aux *aux);
 int drm_dp_start_crc(struct drm_dp_aux *aux, struct drm_crtc *crtc);
 int drm_dp_stop_crc(struct drm_dp_aux *aux);
 
+#ifdef CONFIG_DRM_DP_CEC
+int 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 int drm_dp_cec_irq(struct drm_dp_aux *aux)
+{
+	return 0;
+}
+
+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_ */
-- 
2.11.0
