Applied "spi: spi-fsl-dspi: Use poll mode in case the platform IRQ is missing" to the spi tree

[Mark Brown <broonie@kernel.org>]

The patch

   spi: spi-fsl-dspi: Use poll mode in case the platform IRQ is missing

has been applied to the spi tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-5.4

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

From c55be305915974db160ce6472722ff74f45b8d4e Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <olteanv@gmail.com>
Date: Fri, 23 Aug 2019 00:15:13 +0300
Subject: [PATCH] spi: spi-fsl-dspi: Use poll mode in case the platform IRQ is
 missing

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>
---
 drivers/spi/spi-fsl-dspi.c | 87 ++++++++++++++++++++++++++++----------
 1 file changed, 64 insertions(+), 23 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 6d2c7984ab0e..77db43f1290f 100644
--- 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_dspi *dspi)
 		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 irq, void *dev_id)
 	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(struct spi_controller *ctlr,
 			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);
@@ -1079,10 +1115,13 @@ static int dspi_probe(struct platform_device *pdev)
 		goto out_ctlr_put;
 
 	dspi_init(dspi);
+
 	dspi->irq = platform_get_irq(pdev, 0);
-	if (dspi->irq < 0) {
-		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,
@@ -1092,6 +1131,9 @@ static int dspi_probe(struct platform_device *pdev)
 		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) {
@@ -1103,7 +1145,6 @@ static int dspi_probe(struct platform_device *pdev)
 	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);
-- 
2.20.1