Merge tag 'spi-ptp-api' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi

Pull in a dependency for Vladimir's work on more precise
packet time stamping.

Mark Brown says:

====================
spi: Add a PTP API

For detailed timestamping of operations.
====================

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

2 files changed, 188 insertions, 0 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index f9502dbbb5c1..9bb36c32cbf9 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1171,6 +1171,11 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
 		spi_statistics_add_transfer_stats(statm, xfer, ctlr);
 		spi_statistics_add_transfer_stats(stats, xfer, ctlr);
 
+		if (!ctlr->ptp_sts_supported) {
+			xfer->ptp_sts_word_pre = 0;
+			ptp_read_system_prets(xfer->ptp_sts);
+		}
+
 		if (xfer->tx_buf || xfer->rx_buf) {
 			reinit_completion(&ctlr->xfer_completion);
 
@@ -1197,6 +1202,11 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
 					xfer->len);
 		}
 
+		if (!ctlr->ptp_sts_supported) {
+			ptp_read_system_postts(xfer->ptp_sts);
+			xfer->ptp_sts_word_post = xfer->len;
+		}
+
 		trace_spi_transfer_stop(msg, xfer);
 
 		if (msg->status != -EINPROGRESS)
@@ -1265,6 +1275,7 @@ EXPORT_SYMBOL_GPL(spi_finalize_current_transfer);
  */
 static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 {
+	struct spi_transfer *xfer;
 	struct spi_message *msg;
 	bool was_busy = false;
 	unsigned long flags;
@@ -1391,6 +1402,13 @@ static void __spi_pump_messages(struct spi_controller *ctlr, bool in_kthread)
 		goto out;
 	}
 
+	if (!ctlr->ptp_sts_supported && !ctlr->transfer_one) {
+		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+			xfer->ptp_sts_word_pre = 0;
+			ptp_read_system_prets(xfer->ptp_sts);
+		}
+	}
+
 	ret = ctlr->transfer_one_message(ctlr, msg);
 	if (ret) {
 		dev_err(&ctlr->dev,
@@ -1419,6 +1437,99 @@ static void spi_pump_messages(struct kthread_work *work)
 }
 
 /**
+ * spi_take_timestamp_pre - helper for drivers to collect the beginning of the
+ *			    TX timestamp for the requested byte from the SPI
+ *			    transfer. The frequency with which this function
+ *			    must be called (once per word, once for the whole
+ *			    transfer, once per batch of words etc) is arbitrary
+ *			    as long as the @tx buffer offset is greater than or
+ *			    equal to the requested byte at the time of the
+ *			    call. The timestamp is only taken once, at the
+ *			    first such call. It is assumed that the driver
+ *			    advances its @tx buffer pointer monotonically.
+ * @ctlr: Pointer to the spi_controller structure of the driver
+ * @xfer: Pointer to the transfer being timestamped
+ * @tx: Pointer to the current word within the xfer->tx_buf that the driver is
+ *	preparing to transmit right now.
+ * @irqs_off: If true, will disable IRQs and preemption for the duration of the
+ *	      transfer, for less jitter in time measurement. Only compatible
+ *	      with PIO drivers. If true, must follow up with
+ *	      spi_take_timestamp_post or otherwise system will crash.
+ *	      WARNING: for fully predictable results, the CPU frequency must
+ *	      also be under control (governor).
+ */
+void spi_take_timestamp_pre(struct spi_controller *ctlr,
+			    struct spi_transfer *xfer,
+			    const void *tx, bool irqs_off)
+{
+	u8 bytes_per_word = DIV_ROUND_UP(xfer->bits_per_word, 8);
+
+	if (!xfer->ptp_sts)
+		return;
+
+	if (xfer->timestamped_pre)
+		return;
+
+	if (tx < (xfer->tx_buf + xfer->ptp_sts_word_pre * bytes_per_word))
+		return;
+
+	/* Capture the resolution of the timestamp */
+	xfer->ptp_sts_word_pre = (tx - xfer->tx_buf) / bytes_per_word;
+
+	xfer->timestamped_pre = true;
+
+	if (irqs_off) {
+		local_irq_save(ctlr->irq_flags);
+		preempt_disable();
+	}
+
+	ptp_read_system_prets(xfer->ptp_sts);
+}
+EXPORT_SYMBOL_GPL(spi_take_timestamp_pre);
+
+/**
+ * spi_take_timestamp_post - helper for drivers to collect the end of the
+ *			     TX timestamp for the requested byte from the SPI
+ *			     transfer. Can be called with an arbitrary
+ *			     frequency: only the first call where @tx exceeds
+ *			     or is equal to the requested word will be
+ *			     timestamped.
+ * @ctlr: Pointer to the spi_controller structure of the driver
+ * @xfer: Pointer to the transfer being timestamped
+ * @tx: Pointer to the current word within the xfer->tx_buf that the driver has
+ *	just transmitted.
+ * @irqs_off: If true, will re-enable IRQs and preemption for the local CPU.
+ */
+void spi_take_timestamp_post(struct spi_controller *ctlr,
+			     struct spi_transfer *xfer,
+			     const void *tx, bool irqs_off)
+{
+	u8 bytes_per_word = DIV_ROUND_UP(xfer->bits_per_word, 8);
+
+	if (!xfer->ptp_sts)
+		return;
+
+	if (xfer->timestamped_post)
+		return;
+
+	if (tx < (xfer->tx_buf + xfer->ptp_sts_word_post * bytes_per_word))
+		return;
+
+	ptp_read_system_postts(xfer->ptp_sts);
+
+	if (irqs_off) {
+		local_irq_restore(ctlr->irq_flags);
+		preempt_enable();
+	}
+
+	/* Capture the resolution of the timestamp */
+	xfer->ptp_sts_word_post = (tx - xfer->tx_buf) / bytes_per_word;
+
+	xfer->timestamped_post = true;
+}
+EXPORT_SYMBOL_GPL(spi_take_timestamp_post);
+
+/**
  * spi_set_thread_rt - set the controller to pump at realtime priority
  * @ctlr: controller to boost priority of
  *
@@ -1503,6 +1614,7 @@ EXPORT_SYMBOL_GPL(spi_get_next_queued_message);
  */
 void spi_finalize_current_message(struct spi_controller *ctlr)
 {
+	struct spi_transfer *xfer;
 	struct spi_message *mesg;
 	unsigned long flags;
 	int ret;
@@ -1511,6 +1623,13 @@ void spi_finalize_current_message(struct spi_controller *ctlr)
 	mesg = ctlr->cur_msg;
 	spin_unlock_irqrestore(&ctlr->queue_lock, flags);
 
+	if (!ctlr->ptp_sts_supported && !ctlr->transfer_one) {
+		list_for_each_entry(xfer, &mesg->transfers, transfer_list) {
+			ptp_read_system_postts(xfer->ptp_sts);
+			xfer->ptp_sts_word_post = xfer->len;
+		}
+	}
+
 	spi_unmap_msg(ctlr, mesg);
 
 	if (ctlr->cur_msg_prepared && ctlr->unprepare_message) {
@@ -3273,6 +3392,7 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
 static int __spi_async(struct spi_device *spi, struct spi_message *message)
 {
 	struct spi_controller *ctlr = spi->controller;
+	struct spi_transfer *xfer;
 
 	/*
 	 * Some controllers do not support doing regular SPI transfers. Return
@@ -3288,6 +3408,13 @@ static int __spi_async(struct spi_device *spi, struct spi_message *message)
 
 	trace_spi_message_submit(message);
 
+	if (!ctlr->ptp_sts_supported) {
+		list_for_each_entry(xfer, &message->transfers, transfer_list) {
+			xfer->ptp_sts_word_pre = 0;
+			ptp_read_system_prets(xfer->ptp_sts);
+		}
+	}
+
 	return ctlr->transfer(spi, message);
 }
 
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index af4f265d0f67..27f6b046cf92 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -13,6 +13,7 @@
 #include <linux/completion.h>
 #include <linux/scatterlist.h>
 #include <linux/gpio/consumer.h>
+#include <linux/ptp_clock_kernel.h>
 
 struct dma_chan;
 struct property_entry;
@@ -409,6 +410,12 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  * @fw_translate_cs: If the boot firmware uses different numbering scheme
  *	what Linux expects, this optional hook can be used to translate
  *	between the two.
+ * @ptp_sts_supported: If the driver sets this to true, it must provide a
+ *	time snapshot in @spi_transfer->ptp_sts as close as possible to the
+ *	moment in time when @spi_transfer->ptp_sts_word_pre and
+ *	@spi_transfer->ptp_sts_word_post were transmitted.
+ *	If the driver does not set this, the SPI core takes the snapshot as
+ *	close to the driver hand-over as possible.
  *
  * Each SPI controller can communicate with one or more @spi_device
  * children.  These make a small bus, sharing MOSI, MISO and SCK signals
@@ -604,6 +611,15 @@ struct spi_controller {
 	void			*dummy_tx;
 
 	int (*fw_translate_cs)(struct spi_controller *ctlr, unsigned cs);
+
+	/*
+	 * Driver sets this field to indicate it is able to snapshot SPI
+	 * transfers (needed e.g. for reading the time of POSIX clocks)
+	 */
+	bool			ptp_sts_supported;
+
+	/* Interrupt enable state during PTP system timestamping */
+	unsigned long		irq_flags;
 };
 
 static inline void *spi_controller_get_devdata(struct spi_controller *ctlr)
@@ -644,6 +660,14 @@ extern struct spi_message *spi_get_next_queued_message(struct spi_controller *ct
 extern void spi_finalize_current_message(struct spi_controller *ctlr);
 extern void spi_finalize_current_transfer(struct spi_controller *ctlr);
 
+/* Helper calls for driver to timestamp transfer */
+void spi_take_timestamp_pre(struct spi_controller *ctlr,
+			    struct spi_transfer *xfer,
+			    const void *tx, bool irqs_off);
+void spi_take_timestamp_post(struct spi_controller *ctlr,
+			     struct spi_transfer *xfer,
+			     const void *tx, bool irqs_off);
+
 /* the spi driver core manages memory for the spi_controller classdev */
 extern struct spi_controller *__spi_alloc_controller(struct device *host,
 						unsigned int size, bool slave);
@@ -753,6 +777,35 @@ extern void spi_res_release(struct spi_controller *ctlr,
  * @transfer_list: transfers are sequenced through @spi_message.transfers
  * @tx_sg: Scatterlist for transmit, currently not for client use
  * @rx_sg: Scatterlist for receive, currently not for client use
+ * @ptp_sts_word_pre: The word (subject to bits_per_word semantics) offset
+ *	within @tx_buf for which the SPI device is requesting that the time
+ *	snapshot for this transfer begins. Upon completing the SPI transfer,
+ *	this value may have changed compared to what was requested, depending
+ *	on the available snapshotting resolution (DMA transfer,
+ *	@ptp_sts_supported is false, etc).
+ * @ptp_sts_word_post: See @ptp_sts_word_post. The two can be equal (meaning
+ *	that a single byte should be snapshotted).
+ *	If the core takes care of the timestamp (if @ptp_sts_supported is false
+ *	for this controller), it will set @ptp_sts_word_pre to 0, and
+ *	@ptp_sts_word_post to the length of the transfer. This is done
+ *	purposefully (instead of setting to spi_transfer->len - 1) to denote
+ *	that a transfer-level snapshot taken from within the driver may still
+ *	be of higher quality.
+ * @ptp_sts: Pointer to a memory location held by the SPI slave device where a
+ *	PTP system timestamp structure may lie. If drivers use PIO or their
+ *	hardware has some sort of assist for retrieving exact transfer timing,
+ *	they can (and should) assert @ptp_sts_supported and populate this
+ *	structure using the ptp_read_system_*ts helper functions.
+ *	The timestamp must represent the time at which the SPI slave device has
+ *	processed the word, i.e. the "pre" timestamp should be taken before
+ *	transmitting the "pre" word, and the "post" timestamp after receiving
+ *	transmit confirmation from the controller for the "post" word.
+ * @timestamped_pre: Set by the SPI controller driver to denote it has acted
+ *	upon the @ptp_sts request. Not set when the SPI core has taken care of
+ *	the task. SPI device drivers are free to print a warning if this comes
+ *	back unset and they need the better resolution.
+ * @timestamped_post: See above. The reason why both exist is that these
+ *	booleans are also used to keep state in the core SPI logic.
  *
  * SPI transfers always write the same number of bytes as they read.
  * Protocol drivers should always provide @rx_buf and/or @tx_buf.
@@ -842,6 +895,14 @@ struct spi_transfer {
 
 	u32		effective_speed_hz;
 
+	unsigned int	ptp_sts_word_pre;
+	unsigned int	ptp_sts_word_post;
+
+	struct ptp_system_timestamp *ptp_sts;
+
+	bool		timestamped_pre;
+	bool		timestamped_post;
+
 	struct list_head transfer_list;
 };