Merge remote-tracking branch 'spi/topic/mpc512x' into spi-next

drivers/spi/spi-mpc512x-psc.c

@@ -21,7 +21,6 @@
 #include <linux/interrupt.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
-#include <linux/workqueue.h>
 #include <linux/completion.h>
 #include <linux/io.h>
 #include <linux/delay.h>
@@ -33,24 +32,15 @@
 
 struct mpc512x_psc_spi {
 	void (*cs_control)(struct spi_device *spi, bool on);
-	u32 sysclk;
 
 	/* driver internal data */
 	struct mpc52xx_psc __iomem *psc;
 	struct mpc512x_psc_fifo __iomem *fifo;
 	unsigned int irq;
 	u8 bits_per_word;
-	u8 busy;
 	u32 mclk;
-	u8 eofbyte;
 
-	struct workqueue_struct *workqueue;
-	struct work_struct work;
-
-	struct list_head queue;
-	spinlock_t lock;	/* Message queue lock */
-
-	struct completion done;
+	struct completion txisrdone;
 };
 
 /* controller state */
@@ -136,99 +126,149 @@ static int mpc512x_psc_spi_transfer_rxtx(struct spi_device *spi,
 					 struct spi_transfer *t)
 {
 	struct mpc512x_psc_spi *mps = spi_master_get_devdata(spi->master);
-	struct mpc52xx_psc __iomem *psc = mps->psc;
 	struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
-	size_t len = t->len;
+	size_t tx_len = t->len;
+	size_t rx_len = t->len;
 	u8 *tx_buf = (u8 *)t->tx_buf;
 	u8 *rx_buf = (u8 *)t->rx_buf;
 
 	if (!tx_buf && !rx_buf && t->len)
 		return -EINVAL;
 
-	/* Zero MR2 */
-	in_8(&psc->mode);
-	out_8(&psc->mode, 0x0);
-
-	/* enable transmiter/receiver */
-	out_8(&psc->command, MPC52xx_PSC_TX_ENABLE | MPC52xx_PSC_RX_ENABLE);
-
-	while (len) {
-		int count;
-		int i;
+	while (rx_len || tx_len) {
+		size_t txcount;
 		u8 data;
 		size_t fifosz;
-		int rxcount;
+		size_t rxcount;
+		int rxtries;
 
 		/*
-		 * The number of bytes that can be sent at a time
-		 * depends on the fifo size.
+		 * send the TX bytes in as large a chunk as possible
+		 * but neither exceed the TX nor the RX FIFOs
 		 */
 		fifosz = MPC512x_PSC_FIFO_SZ(in_be32(&fifo->txsz));
-		count = min(fifosz, len);
-
-		for (i = count; i > 0; i--) {
+		txcount = min(fifosz, tx_len);
+		fifosz = MPC512x_PSC_FIFO_SZ(in_be32(&fifo->rxsz));
+		fifosz -= in_be32(&fifo->rxcnt) + 1;
+		txcount = min(fifosz, txcount);
+		if (txcount) {
+
+			/* fill the TX FIFO */
+			while (txcount-- > 0) {
 				data = tx_buf ? *tx_buf++ : 0;
-			if (len == EOFBYTE && t->cs_change)
-				setbits32(&fifo->txcmd, MPC512x_PSC_FIFO_EOF);
+				if (tx_len == EOFBYTE && t->cs_change)
+					setbits32(&fifo->txcmd,
+						  MPC512x_PSC_FIFO_EOF);
 				out_8(&fifo->txdata_8, data);
-			len--;
+				tx_len--;
 			}
 
-		INIT_COMPLETION(mps->done);
-
-		/* interrupt on tx fifo empty */
+			/* have the ISR trigger when the TX FIFO is empty */
+			INIT_COMPLETION(mps->txisrdone);
 			out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
 			out_be32(&fifo->tximr, MPC512x_PSC_FIFO_EMPTY);
+			wait_for_completion(&mps->txisrdone);
+		}
 
-		wait_for_completion(&mps->done);
+		/*
+		 * consume as much RX data as the FIFO holds, while we
+		 * iterate over the transfer's TX data length
+		 *
+		 * only insist in draining all the remaining RX bytes
+		 * when the TX bytes were exhausted (that's at the very
+		 * end of this transfer, not when still iterating over
+		 * the transfer's chunks)
+		 */
+		rxtries = 50;
+		do {
 
-		mdelay(1);
+			/*
+			 * grab whatever was in the FIFO when we started
+			 * looking, don't bother fetching what was added to
+			 * the FIFO while we read from it -- we'll return
+			 * here eventually and prefer sending out remaining
+			 * TX data
+			 */
+			fifosz = in_be32(&fifo->rxcnt);
+			rxcount = min(fifosz, rx_len);
+			while (rxcount-- > 0) {
+				data = in_8(&fifo->rxdata_8);
+				if (rx_buf)
+					*rx_buf++ = data;
+				rx_len--;
+			}
 
-		/* rx fifo should have count bytes in it */
-		rxcount = in_be32(&fifo->rxcnt);
-		if (rxcount != count)
-			mdelay(1);
+			/*
+			 * come back later if there still is TX data to send,
+			 * bail out of the RX drain loop if all of the TX data
+			 * was sent and all of the RX data was received (i.e.
+			 * when the transmission has completed)
+			 */
+			if (tx_len)
+				break;
+			if (!rx_len)
+				break;
 
+			/*
+			 * TX data transmission has completed while RX data
+			 * is still pending -- that's a transient situation
+			 * which depends on wire speed and specific
+			 * hardware implementation details (buffering) yet
+			 * should resolve very quickly
+			 *
+			 * just yield for a moment to not hog the CPU for
+			 * too long when running SPI at low speed
+			 *
+			 * the timeout range is rather arbitrary and tries
+			 * to balance throughput against system load; the
+			 * chosen values result in a minimal timeout of 50
+			 * times 10us and thus work at speeds as low as
+			 * some 20kbps, while the maximum timeout at the
+			 * transfer's end could be 5ms _if_ nothing else
+			 * ticks in the system _and_ RX data still wasn't
+			 * received, which only occurs in situations that
+			 * are exceptional; removing the unpredictability
+			 * of the timeout either decreases throughput
+			 * (longer timeouts), or puts more load on the
+			 * system (fixed short timeouts) or requires the
+			 * use of a timeout API instead of a counter and an
+			 * unknown inner delay
+			 */
+			usleep_range(10, 100);
+
+		} while (--rxtries > 0);
+		if (!tx_len && rx_len && !rxtries) {
+			/*
+			 * not enough RX bytes even after several retries
+			 * and the resulting rather long timeout?
+			 */
 			rxcount = in_be32(&fifo->rxcnt);
-		if (rxcount != count) {
-			dev_warn(&spi->dev, "expected %d bytes in rx fifo "
-				 "but got %d\n", count, rxcount);
+			dev_warn(&spi->dev,
+				 "short xfer, missing %zd RX bytes, FIFO level %zd\n",
+				 rx_len, rxcount);
 		}
 
-		rxcount = min(rxcount, count);
-		for (i = rxcount; i > 0; i--) {
-			data = in_8(&fifo->rxdata_8);
-			if (rx_buf)
-				*rx_buf++ = data;
-		}
-		while (in_be32(&fifo->rxcnt)) {
+		/*
+		 * drain and drop RX data which "should not be there" in
+		 * the first place, for undisturbed transmission this turns
+		 * into a NOP (except for the FIFO level fetch)
+		 */
+		if (!tx_len && !rx_len) {
+			while (in_be32(&fifo->rxcnt))
 				in_8(&fifo->rxdata_8);
 		}
+
 	}
-	/* disable transmiter/receiver and fifo interrupt */
-	out_8(&psc->command, MPC52xx_PSC_TX_DISABLE | MPC52xx_PSC_RX_DISABLE);
-	out_be32(&fifo->tximr, 0);
 	return 0;
 }
 
-static void mpc512x_psc_spi_work(struct work_struct *work)
+static int mpc512x_psc_spi_msg_xfer(struct spi_master *master,
+				    struct spi_message *m)
 {
-	struct mpc512x_psc_spi *mps = container_of(work,
-						   struct mpc512x_psc_spi,
-						   work);
-
-	spin_lock_irq(&mps->lock);
-	mps->busy = 1;
-	while (!list_empty(&mps->queue)) {
-		struct spi_message *m;
 	struct spi_device *spi;
-		struct spi_transfer *t = NULL;
 	unsigned cs_change;
 	int status;
-
-		m = container_of(mps->queue.next, struct spi_message, queue);
-		list_del_init(&m->queue);
-		spin_unlock_irq(&mps->lock);
+	struct spi_transfer *t;
 
 	spi = m->spi;
 	cs_change = 1;
@@ -264,17 +304,45 @@ static void mpc512x_psc_spi_work(struct work_struct *work)
 
 	mpc512x_psc_spi_transfer_setup(spi, NULL);
 
-		spin_lock_irq(&mps->lock);
-	}
-	mps->busy = 0;
-	spin_unlock_irq(&mps->lock);
+	spi_finalize_current_message(master);
+	return status;
+}
+
+static int mpc512x_psc_spi_prep_xfer_hw(struct spi_master *master)
+{
+	struct mpc512x_psc_spi *mps = spi_master_get_devdata(master);
+	struct mpc52xx_psc __iomem *psc = mps->psc;
+
+	dev_dbg(&master->dev, "%s()\n", __func__);
+
+	/* Zero MR2 */
+	in_8(&psc->mode);
+	out_8(&psc->mode, 0x0);
+
+	/* enable transmitter/receiver */
+	out_8(&psc->command, MPC52xx_PSC_TX_ENABLE | MPC52xx_PSC_RX_ENABLE);
+
+	return 0;
+}
+
+static int mpc512x_psc_spi_unprep_xfer_hw(struct spi_master *master)
+{
+	struct mpc512x_psc_spi *mps = spi_master_get_devdata(master);
+	struct mpc52xx_psc __iomem *psc = mps->psc;
+	struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
+
+	dev_dbg(&master->dev, "%s()\n", __func__);
+
+	/* disable transmitter/receiver and fifo interrupt */
+	out_8(&psc->command, MPC52xx_PSC_TX_DISABLE | MPC52xx_PSC_RX_DISABLE);
+	out_be32(&fifo->tximr, 0);
+
+	return 0;
 }
 
 static int mpc512x_psc_spi_setup(struct spi_device *spi)
 {
-	struct mpc512x_psc_spi *mps = spi_master_get_devdata(spi->master);
 	struct mpc512x_psc_spi_cs *cs = spi->controller_state;
-	unsigned long flags;
 	int ret;
 
 	if (spi->bits_per_word % 8)
@@ -303,28 +371,6 @@ static int mpc512x_psc_spi_setup(struct spi_device *spi)
 	cs->bits_per_word = spi->bits_per_word;
 	cs->speed_hz = spi->max_speed_hz;
 
-	spin_lock_irqsave(&mps->lock, flags);
-	if (!mps->busy)
-		mpc512x_psc_spi_deactivate_cs(spi);
-	spin_unlock_irqrestore(&mps->lock, flags);
-
-	return 0;
-}
-
-static int mpc512x_psc_spi_transfer(struct spi_device *spi,
-				    struct spi_message *m)
-{
-	struct mpc512x_psc_spi *mps = spi_master_get_devdata(spi->master);
-	unsigned long flags;
-
-	m->actual_length = 0;
-	m->status = -EINPROGRESS;
-
-	spin_lock_irqsave(&mps->lock, flags);
-	list_add_tail(&m->queue, &mps->queue);
-	queue_work(mps->workqueue, &mps->work);
-	spin_unlock_irqrestore(&mps->lock, flags);
-
 	return 0;
 }
 
@@ -407,12 +453,12 @@ static irqreturn_t mpc512x_psc_spi_isr(int irq, void *dev_id)
 	struct mpc512x_psc_spi *mps = (struct mpc512x_psc_spi *)dev_id;
 	struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
 
-	/* clear interrupt and wake up the work queue */
+	/* clear interrupt and wake up the rx/tx routine */
 	if (in_be32(&fifo->txisr) &
 	    in_be32(&fifo->tximr) & MPC512x_PSC_FIFO_EMPTY) {
 		out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
 		out_be32(&fifo->tximr, 0);
-		complete(&mps->done);
+		complete(&mps->txisrdone);
 		return IRQ_HANDLED;
 	}
 	return IRQ_NONE;
@@ -444,18 +490,18 @@ static int mpc512x_psc_spi_do_probe(struct device *dev, u32 regaddr,
 
 	if (pdata == NULL) {
 		mps->cs_control = mpc512x_spi_cs_control;
-		mps->sysclk = 0;
 		master->bus_num = bus_num;
 	} else {
 		mps->cs_control = pdata->cs_control;
-		mps->sysclk = pdata->sysclk;
 		master->bus_num = pdata->bus_num;
 		master->num_chipselect = pdata->max_chipselect;
 	}
 
 	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
 	master->setup = mpc512x_psc_spi_setup;
-	master->transfer = mpc512x_psc_spi_transfer;
+	master->prepare_transfer_hardware = mpc512x_psc_spi_prep_xfer_hw;
+	master->transfer_one_message = mpc512x_psc_spi_msg_xfer;
+	master->unprepare_transfer_hardware = mpc512x_psc_spi_unprep_xfer_hw;
 	master->cleanup = mpc512x_psc_spi_cleanup;
 	master->dev.of_node = dev->of_node;
 
@@ -473,31 +519,18 @@ static int mpc512x_psc_spi_do_probe(struct device *dev, u32 regaddr,
 			  "mpc512x-psc-spi", mps);
 	if (ret)
 		goto free_master;
+	init_completion(&mps->txisrdone);
 
 	ret = mpc512x_psc_spi_port_config(master, mps);
 	if (ret < 0)
 		goto free_irq;
 
-	spin_lock_init(&mps->lock);
-	init_completion(&mps->done);
-	INIT_WORK(&mps->work, mpc512x_psc_spi_work);
-	INIT_LIST_HEAD(&mps->queue);
-
-	mps->workqueue =
-		create_singlethread_workqueue(dev_name(master->dev.parent));
-	if (mps->workqueue == NULL) {
-		ret = -EBUSY;
-		goto free_irq;
-	}
-
 	ret = spi_register_master(master);
 	if (ret < 0)
-		goto unreg_master;
+		goto free_irq;
 
 	return ret;
 
-unreg_master:
-	destroy_workqueue(mps->workqueue);
 free_irq:
 	free_irq(mps->irq, mps);
 free_master:
@@ -513,8 +546,6 @@ static int mpc512x_psc_spi_do_remove(struct device *dev)
 	struct spi_master *master = spi_master_get(dev_get_drvdata(dev));
 	struct mpc512x_psc_spi *mps = spi_master_get_devdata(master);
 
-	flush_workqueue(mps->workqueue);
-	destroy_workqueue(mps->workqueue);
 	spi_unregister_master(master);
 	free_irq(mps->irq, mps);
 	if (mps->psc)