media: cec-pin: add low-level pin hardware support

Add support for CEC hardware that relies on low-level pin polling or
GPIO interrupts.

One example is the Allwinner SoC. But any GPIO-based CEC implementation can
use this as well.

A GPIO implementation is very suitable as well for debugging: it can use
interrupts to detect state changes and report it. Userspace can then verify
if the bus traffic is correct. This also makes error injection possible.

The disadvantage is that it is hard to get the timings right since linux
isn't a hard realtime system.

In general on an idle system it works quite well, but under load the timer
will miss its mark every so often.

The debugfs file /sys/kernel/debug/cec/cecX/status gives some statistics
with respect to the timer overruns.

When the adapter is unconfigured and the low-level driver supports
interrupts, then the interrupt will be used to detect changes. This should
be quite accurate. But when the adapter is configured a hrtimer has to be
used.

The hrtimer implements a state machine where for each state the code will
read the bus or drive the bus and go on to the next state. It will re-arm
the timer with a delay based on the next state.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/Kconfig

@@ -8,6 +8,9 @@ config CEC_CORE
 config CEC_NOTIFIER
 	bool
 
+config CEC_PIN
+	bool
+
 menuconfig MEDIA_SUPPORT
 	tristate "Multimedia support"
 	depends on HAS_IOMEM

drivers/media/cec/Makefile

@@ -4,4 +4,8 @@ ifeq ($(CONFIG_CEC_NOTIFIER),y)
   cec-objs += cec-notifier.o
 endif
 
+ifeq ($(CONFIG_CEC_PIN),y)
+  cec-objs += cec-pin.o
+endif
+
 obj-$(CONFIG_CEC_CORE) += cec.o

drivers/media/cec/cec-api.c

@@ -30,6 +30,7 @@
 #include <linux/uaccess.h>
 #include <linux/version.h>
 
+#include <media/cec-pin.h>
 #include "cec-priv.h"
 
 static inline struct cec_devnode *cec_devnode_data(struct file *filp)
@@ -430,6 +431,15 @@ static long cec_s_mode(struct cec_adapter *adap, struct cec_fh *fh,
 	if (mode_follower == CEC_MODE_FOLLOWER)
 		adap->follower_cnt++;
 	if (mode_follower == CEC_MODE_MONITOR_PIN) {
+#ifdef CONFIG_CEC_PIN
+		struct cec_event ev = {
+			.flags = CEC_EVENT_FL_INITIAL_STATE,
+		};
+
+		ev.event = adap->pin->cur_value ? CEC_EVENT_PIN_HIGH :
+						  CEC_EVENT_PIN_LOW;
+		cec_queue_event_fh(fh, &ev, 0);
+#endif
 		adap->monitor_pin_cnt++;
 	}
 	if (mode_follower == CEC_MODE_EXCL_FOLLOWER ||

drivers/media/cec/cec-pin.c

+/*
+ * 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/delay.h>
+#include <linux/slab.h>
+#include <linux/sched/types.h>
+
+#include <media/cec-pin.h>
+
+/* All timings are in microseconds */
+
+/* start bit timings */
+#define CEC_TIM_START_BIT_LOW		3700
+#define CEC_TIM_START_BIT_LOW_MIN	3500
+#define CEC_TIM_START_BIT_LOW_MAX	3900
+#define CEC_TIM_START_BIT_TOTAL		4500
+#define CEC_TIM_START_BIT_TOTAL_MIN	4300
+#define CEC_TIM_START_BIT_TOTAL_MAX	4700
+
+/* data bit timings */
+#define CEC_TIM_DATA_BIT_0_LOW		1500
+#define CEC_TIM_DATA_BIT_0_LOW_MIN	1300
+#define CEC_TIM_DATA_BIT_0_LOW_MAX	1700
+#define CEC_TIM_DATA_BIT_1_LOW		600
+#define CEC_TIM_DATA_BIT_1_LOW_MIN	400
+#define CEC_TIM_DATA_BIT_1_LOW_MAX	800
+#define CEC_TIM_DATA_BIT_TOTAL		2400
+#define CEC_TIM_DATA_BIT_TOTAL_MIN	2050
+#define CEC_TIM_DATA_BIT_TOTAL_MAX	2750
+/* earliest safe time to sample the bit state */
+#define CEC_TIM_DATA_BIT_SAMPLE		850
+/* earliest time the bit is back to 1 (T7 + 50) */
+#define CEC_TIM_DATA_BIT_HIGH		1750
+
+/* when idle, sample once per millisecond */
+#define CEC_TIM_IDLE_SAMPLE		1000
+/* when processing the start bit, sample twice per millisecond */
+#define CEC_TIM_START_BIT_SAMPLE	500
+/* when polling for a state change, sample once every 50 micoseconds */
+#define CEC_TIM_SAMPLE			50
+
+#define CEC_TIM_LOW_DRIVE_ERROR		(1.5 * CEC_TIM_DATA_BIT_TOTAL)
+
+struct cec_state {
+	const char * const name;
+	unsigned int usecs;
+};
+
+static const struct cec_state states[CEC_PIN_STATES] = {
+	{ "Off",		   0 },
+	{ "Idle",		   CEC_TIM_IDLE_SAMPLE },
+	{ "Tx Wait",		   CEC_TIM_SAMPLE },
+	{ "Tx Wait for High",	   CEC_TIM_IDLE_SAMPLE },
+	{ "Tx Start Bit Low",	   CEC_TIM_START_BIT_LOW },
+	{ "Tx Start Bit High",	   CEC_TIM_START_BIT_TOTAL - CEC_TIM_START_BIT_LOW },
+	{ "Tx Data 0 Low",	   CEC_TIM_DATA_BIT_0_LOW },
+	{ "Tx Data 0 High",	   CEC_TIM_DATA_BIT_TOTAL - CEC_TIM_DATA_BIT_0_LOW },
+	{ "Tx Data 1 Low",	   CEC_TIM_DATA_BIT_1_LOW },
+	{ "Tx Data 1 High",	   CEC_TIM_DATA_BIT_TOTAL - CEC_TIM_DATA_BIT_1_LOW },
+	{ "Tx Data 1 Pre Sample",  CEC_TIM_DATA_BIT_SAMPLE - CEC_TIM_DATA_BIT_1_LOW },
+	{ "Tx Data 1 Post Sample", CEC_TIM_DATA_BIT_TOTAL - CEC_TIM_DATA_BIT_SAMPLE },
+	{ "Rx Start Bit Low",	   CEC_TIM_SAMPLE },
+	{ "Rx Start Bit High",	   CEC_TIM_SAMPLE },
+	{ "Rx Data Sample",	   CEC_TIM_DATA_BIT_SAMPLE },
+	{ "Rx Data Post Sample",   CEC_TIM_DATA_BIT_HIGH - CEC_TIM_DATA_BIT_SAMPLE },
+	{ "Rx Data High",	   CEC_TIM_SAMPLE },
+	{ "Rx Ack Low",		   CEC_TIM_DATA_BIT_0_LOW },
+	{ "Rx Ack Low Post",	   CEC_TIM_DATA_BIT_HIGH - CEC_TIM_DATA_BIT_0_LOW },
+	{ "Rx Ack High Post",	   CEC_TIM_DATA_BIT_HIGH },
+	{ "Rx Ack Finish",	   CEC_TIM_DATA_BIT_TOTAL_MIN - CEC_TIM_DATA_BIT_HIGH },
+	{ "Rx Low Drive",	   CEC_TIM_LOW_DRIVE_ERROR },
+	{ "Rx Irq",		   0 },
+};
+
+static void cec_pin_update(struct cec_pin *pin, bool v, bool force)
+{
+	if (!force && v == pin->cur_value)
+		return;
+
+	pin->cur_value = v;
+	if (atomic_read(&pin->work_pin_events) < CEC_NUM_PIN_EVENTS) {
+		pin->work_pin_is_high[pin->work_pin_events_wr] = v;
+		pin->work_pin_ts[pin->work_pin_events_wr] = ktime_get();
+		pin->work_pin_events_wr =
+			(pin->work_pin_events_wr + 1) % CEC_NUM_PIN_EVENTS;
+		atomic_inc(&pin->work_pin_events);
+	}
+	wake_up_interruptible(&pin->kthread_waitq);
+}
+
+static bool cec_pin_read(struct cec_pin *pin)
+{
+	bool v = pin->ops->read(pin->adap);
+
+	cec_pin_update(pin, v, false);
+	return v;
+}
+
+static void cec_pin_low(struct cec_pin *pin)
+{
+	pin->ops->low(pin->adap);
+	cec_pin_update(pin, false, false);
+}
+
+static bool cec_pin_high(struct cec_pin *pin)
+{
+	pin->ops->high(pin->adap);
+	return cec_pin_read(pin);
+}
+
+static void cec_pin_to_idle(struct cec_pin *pin)
+{
+	/*
+	 * Reset all status fields, release the bus and
+	 * go to idle state.
+	 */
+	pin->rx_bit = pin->tx_bit = 0;
+	pin->rx_msg.len = 0;
+	memset(pin->rx_msg.msg, 0, sizeof(pin->rx_msg.msg));
+	pin->state = CEC_ST_IDLE;
+	pin->ts = 0;
+}
+
+/*
+ * Handle Transmit-related states
+ *
+ * Basic state changes when transmitting:
+ *
+ * Idle -> Tx Wait (waiting for the end of signal free time) ->
+ *	Tx Start Bit Low -> Tx Start Bit High ->
+ *
+ *   Regular data bits + EOM:
+ *	Tx Data 0 Low -> Tx Data 0 High ->
+ *   or:
+ *	Tx Data 1 Low -> Tx Data 1 High ->
+ *
+ *   First 4 data bits or Ack bit:
+ *	Tx Data 0 Low -> Tx Data 0 High ->
+ *   or:
+ *	Tx Data 1 Low -> Tx Data 1 High -> Tx Data 1 Pre Sample ->
+ *		Tx Data 1 Post Sample ->
+ *
+ *   After the last Ack go to Idle.
+ *
+ * If it detects a Low Drive condition then:
+ *	Tx Wait For High -> Idle
+ *
+ * If it loses arbitration, then it switches to state Rx Data Post Sample.
+ */
+static void cec_pin_tx_states(struct cec_pin *pin, ktime_t ts)
+{
+	bool v;
+	bool is_ack_bit, ack;
+
+	switch (pin->state) {
+	case CEC_ST_TX_WAIT_FOR_HIGH:
+		if (cec_pin_read(pin))
+			cec_pin_to_idle(pin);
+		break;
+
+	case CEC_ST_TX_START_BIT_LOW:
+		pin->state = CEC_ST_TX_START_BIT_HIGH;
+		/* Generate start bit */
+		cec_pin_high(pin);
+		break;
+
+	case CEC_ST_TX_DATA_BIT_1_HIGH_POST_SAMPLE:
+		/* If the read value is 1, then all is OK */
+		if (!cec_pin_read(pin)) {
+			/*
+			 * It's 0, so someone detected an error and pulled the
+			 * line low for 1.5 times the nominal bit period.
+			 */
+			pin->tx_msg.len = 0;
+			pin->work_tx_ts = ts;
+			pin->work_tx_status = CEC_TX_STATUS_LOW_DRIVE;
+			pin->state = CEC_ST_TX_WAIT_FOR_HIGH;
+			wake_up_interruptible(&pin->kthread_waitq);
+			break;
+		}
+		if (pin->tx_nacked) {
+			cec_pin_to_idle(pin);
+			pin->tx_msg.len = 0;
+			pin->work_tx_ts = ts;
+			pin->work_tx_status = CEC_TX_STATUS_NACK;
+			wake_up_interruptible(&pin->kthread_waitq);
+			break;
+		}
+		/* fall through */
+	case CEC_ST_TX_DATA_BIT_0_HIGH:
+	case CEC_ST_TX_DATA_BIT_1_HIGH:
+		pin->tx_bit++;
+		/* fall through */
+	case CEC_ST_TX_START_BIT_HIGH:
+		if (pin->tx_bit / 10 >= pin->tx_msg.len) {
+			cec_pin_to_idle(pin);
+			pin->tx_msg.len = 0;
+			pin->work_tx_ts = ts;
+			pin->work_tx_status = CEC_TX_STATUS_OK;
+			wake_up_interruptible(&pin->kthread_waitq);
+			break;
+		}
+
+		switch (pin->tx_bit % 10) {
+		default:
+			v = pin->tx_msg.msg[pin->tx_bit / 10] &
+				(1 << (7 - (pin->tx_bit % 10)));
+			pin->state = v ? CEC_ST_TX_DATA_BIT_1_LOW :
+				CEC_ST_TX_DATA_BIT_0_LOW;
+			break;
+		case 8:
+			v = pin->tx_bit / 10 == pin->tx_msg.len - 1;
+			pin->state = v ? CEC_ST_TX_DATA_BIT_1_LOW :
+				CEC_ST_TX_DATA_BIT_0_LOW;
+			break;
+		case 9:
+			pin->state = CEC_ST_TX_DATA_BIT_1_LOW;
+			break;
+		}
+		cec_pin_low(pin);
+		break;
+
+	case CEC_ST_TX_DATA_BIT_0_LOW:
+	case CEC_ST_TX_DATA_BIT_1_LOW:
+		v = pin->state == CEC_ST_TX_DATA_BIT_1_LOW;
+		pin->state = v ? CEC_ST_TX_DATA_BIT_1_HIGH :
+			CEC_ST_TX_DATA_BIT_0_HIGH;
+		is_ack_bit = pin->tx_bit % 10 == 9;
+		if (v && (pin->tx_bit < 4 || is_ack_bit))
+			pin->state = CEC_ST_TX_DATA_BIT_1_HIGH_PRE_SAMPLE;
+		cec_pin_high(pin);
+		break;
+
+	case CEC_ST_TX_DATA_BIT_1_HIGH_PRE_SAMPLE:
+		/* Read the CEC value at the sample time */
+		v = cec_pin_read(pin);
+		is_ack_bit = pin->tx_bit % 10 == 9;
+		/*
+		 * If v == 0 and we're within the first 4 bits
+		 * of the initiator, then someone else started
+		 * transmitting and we lost the arbitration
+		 * (i.e. the logical address of the other
+		 * transmitter has more leading 0 bits in the
+		 * initiator).
+		 */
+		if (!v && !is_ack_bit) {
+			pin->tx_msg.len = 0;
+			pin->work_tx_ts = ts;
+			pin->work_tx_status = CEC_TX_STATUS_ARB_LOST;
+			wake_up_interruptible(&pin->kthread_waitq);
+			pin->rx_bit = pin->tx_bit;
+			pin->tx_bit = 0;
+			memset(pin->rx_msg.msg, 0, sizeof(pin->rx_msg.msg));
+			pin->rx_msg.msg[0] = pin->tx_msg.msg[0];
+			pin->rx_msg.msg[0] &= ~(1 << (7 - pin->rx_bit));
+			pin->rx_msg.len = 0;
+			pin->state = CEC_ST_RX_DATA_POST_SAMPLE;
+			pin->rx_bit++;
+			break;
+		}
+		pin->state = CEC_ST_TX_DATA_BIT_1_HIGH_POST_SAMPLE;
+		if (!is_ack_bit)
+			break;
+		/* Was the message ACKed? */
+		ack = cec_msg_is_broadcast(&pin->tx_msg) ? v : !v;
+		if (!ack) {
+			/*
+			 * Note: the CEC spec is ambiguous regarding
+			 * what action to take when a NACK appears
+			 * before the last byte of the payload was
+			 * transmitted: either stop transmitting
+			 * immediately, or wait until the last byte
+			 * was transmitted.
+			 *
+			 * Most CEC implementations appear to stop
+			 * immediately, and that's what we do here
+			 * as well.
+			 */
+			pin->tx_nacked = true;
+		}
+		break;
+
+	default:
+		break;
+	}
+}
+
+/*
+ * Handle Receive-related states
+ *
+ * Basic state changes when receiving:
+ *
+ *	Rx Start Bit Low -> Rx Start Bit High ->
+ *   Regular data bits + EOM:
+ *	Rx Data Sample -> Rx Data Post Sample -> Rx Data High ->
+ *   Ack bit 0:
+ *	Rx Ack Low -> Rx Ack Low Post -> Rx Data High ->
+ *   Ack bit 1:
+ *	Rx Ack High Post -> Rx Data High ->
+ *   Ack bit 0 && EOM:
+ *	Rx Ack Low -> Rx Ack Low Post -> Rx Ack Finish -> Idle
+ */
+static void cec_pin_rx_states(struct cec_pin *pin, ktime_t ts)
+{
+	s32 delta;
+	bool v;
+	bool ack;
+	bool bcast, for_us;
+	u8 dest;
+
+	switch (pin->state) {
+	/* Receive states */
+	case CEC_ST_RX_START_BIT_LOW:
+		v = cec_pin_read(pin);
+		if (!v)
+			break;
+		pin->state = CEC_ST_RX_START_BIT_HIGH;
+		delta = ktime_us_delta(ts, pin->ts);
+		pin->ts = ts;
+		/* Start bit low is too short, go back to idle */
+		if (delta < CEC_TIM_START_BIT_LOW_MIN -
+			    CEC_TIM_IDLE_SAMPLE) {
+			cec_pin_to_idle(pin);
+		}
+		break;
+
+	case CEC_ST_RX_START_BIT_HIGH:
+		v = cec_pin_read(pin);
+		delta = ktime_us_delta(ts, pin->ts);
+		if (v && delta > CEC_TIM_START_BIT_TOTAL_MAX -
+				 CEC_TIM_START_BIT_LOW_MIN) {
+			cec_pin_to_idle(pin);
+			break;
+		}
+		if (v)
+			break;
+		pin->state = CEC_ST_RX_DATA_SAMPLE;
+		pin->ts = ts;
+		pin->rx_eom = false;
+		break;
+
+	case CEC_ST_RX_DATA_SAMPLE:
+		v = cec_pin_read(pin);
+		pin->state = CEC_ST_RX_DATA_POST_SAMPLE;
+		switch (pin->rx_bit % 10) {
+		default:
+			if (pin->rx_bit / 10 < CEC_MAX_MSG_SIZE)
+				pin->rx_msg.msg[pin->rx_bit / 10] |=
+					v << (7 - (pin->rx_bit % 10));
+			break;
+		case 8:
+			pin->rx_eom = v;
+			pin->rx_msg.len = pin->rx_bit / 10 + 1;
+			break;
+		case 9:
+			break;
+		}
+		pin->rx_bit++;
+		break;
+
+	case CEC_ST_RX_DATA_POST_SAMPLE:
+		pin->state = CEC_ST_RX_DATA_HIGH;
+		break;
+
+	case CEC_ST_RX_DATA_HIGH:
+		v = cec_pin_read(pin);
+		delta = ktime_us_delta(ts, pin->ts);
+		if (v && delta > CEC_TIM_DATA_BIT_TOTAL_MAX) {
+			cec_pin_to_idle(pin);
+			break;
+		}
+		if (v)
+			break;
+		/*
+		 * Go to low drive state when the total bit time is
+		 * too short.
+		 */
+		if (delta < CEC_TIM_DATA_BIT_TOTAL_MIN) {
+			cec_pin_low(pin);
+			pin->state = CEC_ST_LOW_DRIVE;
+			break;
+		}
+		pin->ts = ts;
+		if (pin->rx_bit % 10 != 9) {
+			pin->state = CEC_ST_RX_DATA_SAMPLE;
+			break;
+		}
+
+		dest = cec_msg_destination(&pin->rx_msg);
+		bcast = dest == CEC_LOG_ADDR_BROADCAST;
+		/* for_us == broadcast or directed to us */
+		for_us = bcast || (pin->la_mask & (1 << dest));
+		/* ACK bit value */
+		ack = bcast ? 1 : !for_us;
+
+		if (ack) {
+			/* No need to write to the bus, just wait */
+			pin->state = CEC_ST_RX_ACK_HIGH_POST;
+			break;
+		}
+		cec_pin_low(pin);
+		pin->state = CEC_ST_RX_ACK_LOW;
+		break;
+
+	case CEC_ST_RX_ACK_LOW:
+		cec_pin_high(pin);
+		pin->state = CEC_ST_RX_ACK_LOW_POST;
+		break;
+
+	case CEC_ST_RX_ACK_LOW_POST:
+	case CEC_ST_RX_ACK_HIGH_POST:
+		v = cec_pin_read(pin);
+		if (v && pin->rx_eom) {
+			pin->work_rx_msg = pin->rx_msg;
+			pin->work_rx_msg.rx_ts = ts;
+			wake_up_interruptible(&pin->kthread_waitq);
+			pin->ts = ts;
+			pin->state = CEC_ST_RX_ACK_FINISH;
+			break;
+		}
+		pin->rx_bit++;
+		pin->state = CEC_ST_RX_DATA_HIGH;
+		break;
+
+	case CEC_ST_RX_ACK_FINISH:
+		cec_pin_to_idle(pin);
+		break;
+
+	default:
+		break;
+	}
+}
+
+/*
+ * Main timer function
+ *
+ */
+static enum hrtimer_restart cec_pin_timer(struct hrtimer *timer)
+{
+	struct cec_pin *pin = container_of(timer, struct cec_pin, timer);
+	struct cec_adapter *adap = pin->adap;
+	ktime_t ts;
+	s32 delta;
+
+	ts = ktime_get();
+	if (pin->timer_ts) {
+		delta = ktime_us_delta(ts, pin->timer_ts);
+		pin->timer_cnt++;
+		if (delta > 100 && pin->state != CEC_ST_IDLE) {
+			/* Keep track of timer overruns */
+			pin->timer_sum_overrun += delta;
+			pin->timer_100ms_overruns++;
+			if (delta > 300)
+				pin->timer_300ms_overruns++;
+			if (delta > pin->timer_max_overrun)
+				pin->timer_max_overrun = delta;
+		}
+	}
+	if (adap->monitor_pin_cnt)
+		cec_pin_read(pin);
+
+	if (pin->wait_usecs) {
+		/*
+		 * If we are monitoring the pin, then we have to
+		 * sample at regular intervals.
+		 */
+		if (pin->wait_usecs > 150) {
+			pin->wait_usecs -= 100;
+			pin->timer_ts = ktime_add_us(ts, 100);
+			hrtimer_forward_now(timer, 100000);
+			return HRTIMER_RESTART;
+		}
+		if (pin->wait_usecs > 100) {
+			pin->wait_usecs /= 2;
+			pin->timer_ts = ktime_add_us(ts, pin->wait_usecs);
+			hrtimer_forward_now(timer, pin->wait_usecs * 1000);
+			return HRTIMER_RESTART;
+		}
+		pin->timer_ts = ktime_add_us(ts, pin->wait_usecs);
+		hrtimer_forward_now(timer, pin->wait_usecs * 1000);
+		pin->wait_usecs = 0;
+		return HRTIMER_RESTART;
+	}
+
+	switch (pin->state) {
+	/* Transmit states */
+	case CEC_ST_TX_WAIT_FOR_HIGH:
+	case CEC_ST_TX_START_BIT_LOW:
+	case CEC_ST_TX_DATA_BIT_1_HIGH_POST_SAMPLE:
+	case CEC_ST_TX_DATA_BIT_0_HIGH:
+	case CEC_ST_TX_DATA_BIT_1_HIGH:
+	case CEC_ST_TX_START_BIT_HIGH:
+	case CEC_ST_TX_DATA_BIT_0_LOW:
+	case CEC_ST_TX_DATA_BIT_1_LOW:
+	case CEC_ST_TX_DATA_BIT_1_HIGH_PRE_SAMPLE:
+		cec_pin_tx_states(pin, ts);
+		break;
+
+	/* Receive states */
+	case CEC_ST_RX_START_BIT_LOW:
+	case CEC_ST_RX_START_BIT_HIGH:
+	case CEC_ST_RX_DATA_SAMPLE:
+	case CEC_ST_RX_DATA_POST_SAMPLE:
+	case CEC_ST_RX_DATA_HIGH:
+	case CEC_ST_RX_ACK_LOW:
+	case CEC_ST_RX_ACK_LOW_POST:
+	case CEC_ST_RX_ACK_HIGH_POST:
+	case CEC_ST_RX_ACK_FINISH:
+		cec_pin_rx_states(pin, ts);
+		break;
+
+	case CEC_ST_IDLE:
+	case CEC_ST_TX_WAIT:
+		if (!cec_pin_high(pin)) {
+			/* Start bit, switch to receive state */
+			pin->ts = ts;
+			pin->state = CEC_ST_RX_START_BIT_LOW;
+			break;
+		}
+		if (pin->ts == 0)
+			pin->ts = ts;
+		if (pin->tx_msg.len) {
+			/*
+			 * Check if the bus has been free for long enough
+			 * so we can kick off the pending transmit.
+			 */
+			delta = ktime_us_delta(ts, pin->ts);
+			if (delta / CEC_TIM_DATA_BIT_TOTAL >
+			    pin->tx_signal_free_time) {
+				pin->tx_nacked = false;
+				pin->state = CEC_ST_TX_START_BIT_LOW;
+				/* Generate start bit */
+				cec_pin_low(pin);
+				break;
+			}
+			if (delta / CEC_TIM_DATA_BIT_TOTAL >
+			    pin->tx_signal_free_time - 1)
+				pin->state = CEC_ST_TX_WAIT;
+			break;
+		}
+		if (pin->state != CEC_ST_IDLE || pin->ops->enable_irq == NULL ||
+		    pin->enable_irq_failed || adap->is_configuring ||
+		    adap->is_configured || adap->monitor_all_cnt)
+			break;
+		/* Switch to interrupt mode */
+		pin->work_enable_irq = true;
+		pin->state = CEC_ST_RX_IRQ;
+		wake_up_interruptible(&pin->kthread_waitq);
+		return HRTIMER_NORESTART;
+
+	case CEC_ST_LOW_DRIVE:
+		cec_pin_to_idle(pin);
+		break;
+
+	default:
+		break;
+	}
+	if (!adap->monitor_pin_cnt || states[pin->state].usecs <= 150) {
+		pin->wait_usecs = 0;
+		pin->timer_ts = ktime_add_us(ts, states[pin->state].usecs);
+		hrtimer_forward_now(timer, states[pin->state].usecs * 1000);
+		return HRTIMER_RESTART;
+	}
+	pin->wait_usecs = states[pin->state].usecs - 100;
+	pin->timer_ts = ktime_add_us(ts, 100);
+	hrtimer_forward_now(timer, 100000);
+	return HRTIMER_RESTART;
+}
+
+static int cec_pin_thread_func(void *_adap)
+{
+	struct cec_adapter *adap = _adap;
+	struct cec_pin *pin = adap->pin;
+
+	for (;;) {
+		wait_event_interruptible(pin->kthread_waitq,
+			kthread_should_stop() ||
+			pin->work_rx_msg.len ||
+			pin->work_tx_status ||
+			pin->work_enable_irq ||
+			atomic_read(&pin->work_pin_events));
+
+		if (pin->work_rx_msg.len) {
+			cec_received_msg_ts(adap, &pin->work_rx_msg,
+					    pin->work_rx_msg.rx_ts);
+			pin->work_rx_msg.len = 0;
+		}
+		if (pin->work_tx_status) {
+			unsigned int tx_status = pin->work_tx_status;
+
+			pin->work_tx_status = 0;
+			cec_transmit_attempt_done_ts(adap, tx_status,
+						     pin->work_tx_ts);
+		}
+		while (atomic_read(&pin->work_pin_events)) {
+			unsigned int idx = pin->work_pin_events_rd;
+
+			cec_queue_pin_event(adap, pin->work_pin_is_high[idx],
+					    pin->work_pin_ts[idx]);
+			pin->work_pin_events_rd = (idx + 1) % CEC_NUM_PIN_EVENTS;
+			atomic_dec(&pin->work_pin_events);
+		}
+		if (pin->work_enable_irq) {
+			pin->work_enable_irq = false;
+			pin->enable_irq_failed = !pin->ops->enable_irq(adap);
+			if (pin->enable_irq_failed) {
+				cec_pin_to_idle(pin);
+				hrtimer_start(&pin->timer, 0, HRTIMER_MODE_REL);
+			}
+		}
+		if (kthread_should_stop())
+			break;
+	}
+	return 0;
+}
+
+static int cec_pin_adap_enable(struct cec_adapter *adap, bool enable)
+{
+	struct cec_pin *pin = adap->pin;
+
+	pin->enabled = enable;
+	if (enable) {
+		atomic_set(&pin->work_pin_events, 0);
+		pin->work_pin_events_rd = pin->work_pin_events_wr = 0;
+		cec_pin_read(pin);
+		cec_pin_to_idle(pin);
+		pin->tx_msg.len = 0;
+		pin->timer_ts = 0;
+		pin->work_enable_irq = false;
+		pin->kthread = kthread_run(cec_pin_thread_func, adap,
+					   "cec-pin");
+		if (IS_ERR(pin->kthread)) {
+			pr_err("cec-pin: kernel_thread() failed\n");
+			return PTR_ERR(pin->kthread);
+		}
+		hrtimer_start(&pin->timer, 0, HRTIMER_MODE_REL);
+	} else {
+		if (pin->ops->disable_irq)
+			pin->ops->disable_irq(adap);
+		hrtimer_cancel(&pin->timer);
+		kthread_stop(pin->kthread);
+		cec_pin_read(pin);
+		cec_pin_to_idle(pin);
+		pin->state = CEC_ST_OFF;
+	}
+	return 0;
+}
+
+static int cec_pin_adap_log_addr(struct cec_adapter *adap, u8 log_addr)
+{
+	struct cec_pin *pin = adap->pin;
+
+	if (log_addr == CEC_LOG_ADDR_INVALID)
+		pin->la_mask = 0;
+	else
+		pin->la_mask |= (1 << log_addr);
+	return 0;
+}
+
+static int cec_pin_adap_transmit(struct cec_adapter *adap, u8 attempts,
+				      u32 signal_free_time, struct cec_msg *msg)
+{
+	struct cec_pin *pin = adap->pin;
+
+	pin->tx_signal_free_time = signal_free_time;
+	pin->tx_msg = *msg;
+	pin->work_tx_status = 0;
+	pin->tx_bit = 0;
+	if (pin->state == CEC_ST_RX_IRQ) {
+		pin->work_enable_irq = false;
+		pin->ops->disable_irq(adap);
+		cec_pin_high(pin);
+		cec_pin_to_idle(pin);
+		hrtimer_start(&pin->timer, 0, HRTIMER_MODE_REL);
+	}
+	return 0;
+}
+
+static void cec_pin_adap_status(struct cec_adapter *adap,
+				       struct seq_file *file)
+{
+	struct cec_pin *pin = adap->pin;
+
+	seq_printf(file, "state:   %s\n", states[pin->state].name);
+	seq_printf(file, "tx_bit:  %d\n", pin->tx_bit);
+	seq_printf(file, "rx_bit:  %d\n", pin->rx_bit);
+	seq_printf(file, "cec pin: %d\n", pin->ops->read(adap));
+	seq_printf(file, "irq failed: %d\n", pin->enable_irq_failed);
+	if (pin->timer_100ms_overruns) {
+		seq_printf(file, "timer overruns > 100ms: %u of %u\n",
+			   pin->timer_100ms_overruns, pin->timer_cnt);
+		seq_printf(file, "timer overruns > 300ms: %u of %u\n",
+			   pin->timer_300ms_overruns, pin->timer_cnt);
+		seq_printf(file, "max timer overrun: %u usecs\n",
+			   pin->timer_max_overrun);
+		seq_printf(file, "avg timer overrun: %u usecs\n",
+			   pin->timer_sum_overrun / pin->timer_100ms_overruns);
+	}
+	pin->timer_cnt = 0;
+	pin->timer_100ms_overruns = 0;
+	pin->timer_300ms_overruns = 0;
+	pin->timer_max_overrun = 0;
+	pin->timer_sum_overrun = 0;
+	if (pin->ops->status)
+		pin->ops->status(adap, file);
+}
+
+static int cec_pin_adap_monitor_all_enable(struct cec_adapter *adap,
+						  bool enable)
+{
+	struct cec_pin *pin = adap->pin;
+
+	pin->monitor_all = enable;
+	return 0;
+}
+
+static void cec_pin_adap_free(struct cec_adapter *adap)
+{
+	struct cec_pin *pin = adap->pin;
+
+	if (pin->ops->free)
+		pin->ops->free(adap);
+	adap->pin = NULL;
+	kfree(pin);
+}
+
+void cec_pin_changed(struct cec_adapter *adap, bool value)
+{
+	struct cec_pin *pin = adap->pin;
+
+	cec_pin_update(pin, value, false);
+	if (!value && (adap->is_configuring || adap->is_configured ||
+		       adap->monitor_all_cnt)) {
+		pin->work_enable_irq = false;
+		pin->ops->disable_irq(adap);
+		cec_pin_high(pin);
+		cec_pin_to_idle(pin);
+		hrtimer_start(&pin->timer, 0, HRTIMER_MODE_REL);
+	}
+}
+EXPORT_SYMBOL_GPL(cec_pin_changed);
+
+static const struct cec_adap_ops cec_pin_adap_ops = {
+	.adap_enable = cec_pin_adap_enable,
+	.adap_monitor_all_enable = cec_pin_adap_monitor_all_enable,
+	.adap_log_addr = cec_pin_adap_log_addr,
+	.adap_transmit = cec_pin_adap_transmit,
+	.adap_status = cec_pin_adap_status,
+	.adap_free = cec_pin_adap_free,
+};
+
+struct cec_adapter *cec_pin_allocate_adapter(const struct cec_pin_ops *pin_ops,
+					void *priv, const char *name, u32 caps)
+{
+	struct cec_adapter *adap;
+	struct cec_pin *pin = kzalloc(sizeof(*pin), GFP_KERNEL);
+
+	if (pin == NULL)
+		return ERR_PTR(-ENOMEM);
+	pin->ops = pin_ops;
+	pin->cur_value = true;
+	hrtimer_init(&pin->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	pin->timer.function = cec_pin_timer;
+	init_waitqueue_head(&pin->kthread_waitq);
+
+	adap = cec_allocate_adapter(&cec_pin_adap_ops, priv, name,
+			    caps | CEC_CAP_MONITOR_ALL | CEC_CAP_MONITOR_PIN,
+			    CEC_MAX_LOG_ADDRS);
+
+	if (PTR_ERR_OR_ZERO(adap)) {
+		kfree(pin);
+		return adap;
+	}
+
+	adap->pin = pin;
+	pin->adap = adap;
+	cec_pin_update(pin, cec_pin_high(pin), true);
+	return adap;
+}
+EXPORT_SYMBOL_GPL(cec_pin_allocate_adapter);

include/media/cec-pin.h

+/*
+ * cec-pin.h - low-level CEC pin control
+ *
+ * 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.
+ */
+
+#ifndef LINUX_CEC_PIN_H
+#define LINUX_CEC_PIN_H
+
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <media/cec.h>
+
+enum cec_pin_state {
+	/* CEC is off */
+	CEC_ST_OFF,
+	/* CEC is idle, waiting for Rx or Tx */
+	CEC_ST_IDLE,
+
+	/* Tx states */
+
+	/* Pending Tx, waiting for Signal Free Time to expire */
+	CEC_ST_TX_WAIT,
+	/* Low-drive was detected, wait for bus to go high */
+	CEC_ST_TX_WAIT_FOR_HIGH,
+	/* Drive CEC low for the start bit */
+	CEC_ST_TX_START_BIT_LOW,
+	/* Drive CEC high for the start bit */
+	CEC_ST_TX_START_BIT_HIGH,
+	/* Drive CEC low for the 0 bit */
+	CEC_ST_TX_DATA_BIT_0_LOW,
+	/* Drive CEC high for the 0 bit */
+	CEC_ST_TX_DATA_BIT_0_HIGH,
+	/* Drive CEC low for the 1 bit */
+	CEC_ST_TX_DATA_BIT_1_LOW,
+	/* Drive CEC high for the 1 bit */
+	CEC_ST_TX_DATA_BIT_1_HIGH,
+	/*
+	 * Wait for start of sample time to check for Ack bit or first
+	 * four initiator bits to check for Arbitration Lost.
+	 */
+	CEC_ST_TX_DATA_BIT_1_HIGH_PRE_SAMPLE,
+	/* Wait for end of bit period after sampling */
+	CEC_ST_TX_DATA_BIT_1_HIGH_POST_SAMPLE,
+
+	/* Rx states */
+
+	/* Start bit low detected */
+	CEC_ST_RX_START_BIT_LOW,
+	/* Start bit high detected */
+	CEC_ST_RX_START_BIT_HIGH,
+	/* Wait for bit sample time */
+	CEC_ST_RX_DATA_SAMPLE,
+	/* Wait for earliest end of bit period after sampling */
+	CEC_ST_RX_DATA_POST_SAMPLE,
+	/* Wait for CEC to go high (i.e. end of bit period */
+	CEC_ST_RX_DATA_HIGH,
+	/* Drive CEC low to send 0 Ack bit */
+	CEC_ST_RX_ACK_LOW,
+	/* End of 0 Ack time, wait for earliest end of bit period */
+	CEC_ST_RX_ACK_LOW_POST,
+	/* Wait for CEC to go high (i.e. end of bit period */
+	CEC_ST_RX_ACK_HIGH_POST,
+	/* Wait for earliest end of bit period and end of message */
+	CEC_ST_RX_ACK_FINISH,
+
+	/* Start low drive */
+	CEC_ST_LOW_DRIVE,
+	/* Monitor pin using interrupts */
+	CEC_ST_RX_IRQ,
+
+	/* Total number of pin states */
+	CEC_PIN_STATES
+};
+
+/**
+ * struct cec_pin_ops - low-level CEC pin operations
+ * @read:	read the CEC pin. Return true if high, false if low.
+ * @low:	drive the CEC pin low.
+ * @high:	stop driving the CEC pin. The pull-up will drive the pin
+ *		high, unless someone else is driving the pin low.
+ * @enable_irq:	optional, enable the interrupt to detect pin voltage changes.
+ * @disable_irq: optional, disable the interrupt.
+ * @free:	optional. Free any allocated resources. Called when the
+ *		adapter is deleted.
+ * @status:	optional, log status information.
+ *
+ * These operations are used by the cec pin framework to manipulate
+ * the CEC pin.
+ */
+struct cec_pin_ops {
+	bool (*read)(struct cec_adapter *adap);
+	void (*low)(struct cec_adapter *adap);
+	void (*high)(struct cec_adapter *adap);
+	bool (*enable_irq)(struct cec_adapter *adap);
+	void (*disable_irq)(struct cec_adapter *adap);
+	void (*free)(struct cec_adapter *adap);
+	void (*status)(struct cec_adapter *adap, struct seq_file *file);
+};
+
+#define CEC_NUM_PIN_EVENTS 128
+
+struct cec_pin {
+	struct cec_adapter		*adap;
+	const struct cec_pin_ops	*ops;
+	struct task_struct		*kthread;
+	wait_queue_head_t		kthread_waitq;
+	struct hrtimer			timer;
+	ktime_t				ts;
+	unsigned int			wait_usecs;
+	u16				la_mask;
+	bool				enabled;
+	bool				monitor_all;
+	bool				cur_value;
+	bool				rx_eom;
+	bool				enable_irq_failed;
+	enum cec_pin_state		state;
+	struct cec_msg			tx_msg;
+	u32				tx_bit;
+	bool				tx_nacked;
+	u32				tx_signal_free_time;
+	struct cec_msg			rx_msg;
+	u32				rx_bit;
+
+	struct cec_msg			work_rx_msg;
+	u8				work_tx_status;
+	bool				work_enable_irq;
+	ktime_t				work_tx_ts;
+	atomic_t			work_pin_events;
+	unsigned int			work_pin_events_wr;
+	unsigned int			work_pin_events_rd;
+	ktime_t				work_pin_ts[CEC_NUM_PIN_EVENTS];
+	bool				work_pin_is_high[CEC_NUM_PIN_EVENTS];
+	ktime_t				timer_ts;
+	u32				timer_cnt;
+	u32				timer_100ms_overruns;
+	u32				timer_300ms_overruns;
+	u32				timer_max_overrun;
+	u32				timer_sum_overrun;
+};
+
+/**
+ * cec_pin_changed() - update pin state from interrupt
+ *
+ * @adap:	pointer to the cec adapter
+ * @value:	when true the pin is high, otherwise it is low
+ *
+ * If changes of the CEC voltage are detected via an interrupt, then
+ * cec_pin_changed is called from the interrupt with the new value.
+ */
+void cec_pin_changed(struct cec_adapter *adap, bool value);
+
+/**
+ * cec_pin_allocate_adapter() - allocate a pin-based cec adapter
+ *
+ * @pin_ops:	low-level pin operations
+ * @priv:	will be stored in adap->priv and can be used by the adapter ops.
+ *		Use cec_get_drvdata(adap) to get the priv pointer.
+ * @name:	the name of the CEC adapter. Note: this name will be copied.
+ * @caps:	capabilities of the CEC adapter. This will be ORed with
+ *		CEC_CAP_MONITOR_ALL and CEC_CAP_MONITOR_PIN.
+ *
+ * Allocate a cec adapter using the cec pin framework.
+ *
+ * Return: a pointer to the cec adapter or an error pointer
+ */
+struct cec_adapter *cec_pin_allocate_adapter(const struct cec_pin_ops *pin_ops,
+					void *priv, const char *name, u32 caps);
+
+#endif

include/media/cec.h

@@ -61,6 +61,7 @@ struct cec_devnode {
 
 struct cec_adapter;
 struct cec_data;
+struct cec_pin;
 
 struct cec_data {
 	struct list_head list;
@@ -189,6 +190,9 @@ struct cec_adapter {
 #ifdef CONFIG_CEC_NOTIFIER
 	struct cec_notifier *notifier;
 #endif
+#ifdef CONFIG_CEC_PIN
+	struct cec_pin *pin;
+#endif
 
 	struct dentry *cec_dir;
 	struct dentry *status_file;