From: Vladimir Oltean <olteanv@gmail.com>
Date: Fri, 23 Aug 2019 00:15:13 +0300
Subject: spi: spi-fsl-dspi: Use poll mode in case the platform IRQ is missing

Git-commit: c55be305915974db160ce6472722ff74f45b8d4e
Patch-mainline: v5.4-rc1
References: bsc#1167260

On platforms like LS1021A which use TCFQ mode, an interrupt needs to be
processed after each byte is TXed/RXed. I tried to make the DSPI
implementation on this SoC operate in other, more efficient modes (EOQ,
DMA) but it looks like it simply isn't possible.

Therefore allow the driver to operate in poll mode, to ease a bit of
this absurd amount of IRQ load generated in TCFQ mode. Doing so reduces
both the net time it takes to transmit a SPI message, as well as the
inter-frame jitter that occurs while doing so.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20190822211514.19288-5-olteanv@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 drivers/spi/spi-fsl-dspi.c |   88 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 64 insertions(+), 24 deletions(-)

--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -647,19 +647,12 @@ static void dspi_eoq_read(struct fsl_dsp
 		dspi_push_rx(dspi, fifo_read(dspi));
 }
 
-static irqreturn_t dspi_interrupt(int irq, void *dev_id)
+static int dspi_rxtx(struct fsl_dspi *dspi)
 {
-	struct fsl_dspi *dspi = (struct fsl_dspi *)dev_id;
 	struct spi_message *msg = dspi->cur_msg;
 	enum dspi_trans_mode trans_mode;
-	u32 spi_sr, spi_tcr;
 	u16 spi_tcnt;
-
-	regmap_read(dspi->regmap, SPI_SR, &spi_sr);
-	regmap_write(dspi->regmap, SPI_SR, spi_sr);
-
-	if (!(spi_sr & (SPI_SR_EOQF | SPI_SR_TCFQF)))
-		return IRQ_NONE;
+	u32 spi_tcr;
 
 	/* Get transfer counter (in number of SPI transfers). It was
 	 * reset to 0 when transfer(s) were started.
@@ -675,17 +668,55 @@ static irqreturn_t dspi_interrupt(int ir
 	else if (trans_mode == DSPI_TCFQ_MODE)
 		dspi_tcfq_read(dspi);
 
-	if (!dspi->len) {
-		dspi->waitflags = 1;
-		wake_up_interruptible(&dspi->waitq);
-		return IRQ_HANDLED;
-	}
+	if (!dspi->len)
+		/* Success! */
+		return 0;
 
 	if (trans_mode == DSPI_EOQ_MODE)
 		dspi_eoq_write(dspi);
 	else if (trans_mode == DSPI_TCFQ_MODE)
 		dspi_tcfq_write(dspi);
 
+	return -EINPROGRESS;
+}
+
+static int dspi_poll(struct fsl_dspi *dspi)
+{
+	int tries = 1000;
+	u32 spi_sr;
+
+	do {
+		regmap_read(dspi->regmap, SPI_SR, &spi_sr);
+		regmap_write(dspi->regmap, SPI_SR, spi_sr);
+
+		if (spi_sr & (SPI_SR_EOQF | SPI_SR_TCFQF))
+			break;
+	} while (--tries);
+
+	if (!tries)
+		return -ETIMEDOUT;
+
+	return dspi_rxtx(dspi);
+}
+
+static irqreturn_t dspi_interrupt(int irq, void *dev_id)
+{
+	struct fsl_dspi *dspi = (struct fsl_dspi *)dev_id;
+	u32 spi_sr;
+
+	regmap_read(dspi->regmap, SPI_SR, &spi_sr);
+	regmap_write(dspi->regmap, SPI_SR, spi_sr);
+
+	if (!(spi_sr & (SPI_SR_EOQF | SPI_SR_TCFQF)))
+		return IRQ_NONE;
+
+	dspi_rxtx(dspi);
+
+	if (!dspi->len) {
+		dspi->waitflags = 1;
+		wake_up_interruptible(&dspi->waitq);
+	}
+
 	return IRQ_HANDLED;
 }
 
@@ -773,13 +804,18 @@ static int dspi_transfer_one_message(str
 			goto out;
 		}
 
-		if (trans_mode != DSPI_DMA_MODE) {
-			if (wait_event_interruptible(dspi->waitq,
-						     dspi->waitflags))
-				dev_err(&dspi->pdev->dev,
-					"wait transfer complete fail!\n");
+		if (!dspi->irq) {
+			do {
+				status = dspi_poll(dspi);
+			} while (status == -EINPROGRESS);
+		} else if (trans_mode != DSPI_DMA_MODE) {
+			status = wait_event_interruptible(dspi->waitq,
+							  dspi->waitflags);
 			dspi->waitflags = 0;
 		}
+		if (status)
+			dev_err(&dspi->pdev->dev,
+				"Waiting for transfer to complete failed!\n");
 
 		if (transfer->delay_usecs)
 			udelay(transfer->delay_usecs);
@@ -1079,11 +1115,13 @@ static int dspi_probe(struct platform_de
 		goto out_ctlr_put;
 
 	dspi_init(dspi);
+
 	dspi->irq = platform_get_irq(pdev, 0);
-	if (dspi->irq < 0) {
-		dev_err(&pdev->dev, "can't get platform irq\n");
-		ret = dspi->irq;
-		goto out_clk_put;
+	if (dspi->irq <= 0) {
+		dev_info(&pdev->dev,
+			 "can't get platform irq, using poll mode\n");
+		dspi->irq = 0;
+		goto poll_mode;
 	}
 
 	ret = devm_request_irq(&pdev->dev, dspi->irq, dspi_interrupt,
@@ -1093,6 +1131,9 @@ static int dspi_probe(struct platform_de
 		goto out_clk_put;
 	}
 
+	init_waitqueue_head(&dspi->waitq);
+
+poll_mode:
 	if (dspi->devtype_data->trans_mode == DSPI_DMA_MODE) {
 		ret = dspi_request_dma(dspi, res->start);
 		if (ret < 0) {
@@ -1104,7 +1145,6 @@ static int dspi_probe(struct platform_de
 	ctlr->max_speed_hz =
 		clk_get_rate(dspi->clk) / dspi->devtype_data->max_clock_factor;
 
-	init_waitqueue_head(&dspi->waitq);
 	platform_set_drvdata(pdev, ctlr);
 
 	ret = spi_register_controller(ctlr);