Applied "spi: lpspi: Add slave mode support" to the spi tree

[Mark Brown <broonie@xxxxxxxxxx>]

The patch

   spi: lpspi: Add slave mode support

has been applied to the spi tree at

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

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 bcd87317aae26b9ac497cbc1232783aaea1aeed4 Mon Sep 17 00:00:00 2001
From: Clark Wang <xiaoning.wang@xxxxxxx>
Date: Fri, 7 Dec 2018 02:50:36 +0000
Subject: [PATCH] spi: lpspi: Add slave mode support

Add slave mode support to the fsl-lpspi driver, only in PIO mode.

For now, there are some limitations for slave mode transmission:
1. The stale data in RXFIFO will be dropped when the Slave does any new
   transfer.
2. One transfer can be finished only after all transfer->len data been
   transferred to master device
3. Slave device only accepts transfer->len data. Any data longer than
   this from master device will be dropped. Any data shorter than this
   from master will cause LPSPI to stuck due to mentioned limitation 2.
4. Only PIO transfer is supported in Slave Mode.

Wire connection:
GND, SCK, MISO(to MISO of slave), MOSI(to MOSI of slave), SCS

Signed-off-by: Clark Wang <xiaoning.wang@xxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 drivers/spi/spi-fsl-lpspi.c | 107 ++++++++++++++++++++++++++----------
 1 file changed, 79 insertions(+), 28 deletions(-)

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 725d6ac5f814..cbf165e7bd17 100644
--- a/drivers/spi/spi-fsl-lpspi.c
+++ b/drivers/spi/spi-fsl-lpspi.c
@@ -55,6 +55,7 @@
 #define IER_RDIE	BIT(1)
 #define IER_TDIE	BIT(0)
 #define CFGR1_PCSCFG	BIT(27)
+#define CFGR1_PINCFG	(BIT(24)|BIT(25))
 #define CFGR1_PCSPOL	BIT(8)
 #define CFGR1_NOSTALL	BIT(3)
 #define CFGR1_MASTER	BIT(0)
@@ -80,6 +81,7 @@ struct fsl_lpspi_data {
 	struct device *dev;
 	void __iomem *base;
 	struct clk *clk;
+	bool is_slave;
 
 	void *rx_buf;
 	const void *tx_buf;
@@ -92,6 +94,8 @@ struct fsl_lpspi_data {
 
 	struct lpspi_config config;
 	struct completion xfer_done;
+
+	bool slave_aborted;
 };
 
 static const struct of_device_id fsl_lpspi_dt_ids[] = {
@@ -206,21 +210,22 @@ static void fsl_lpspi_set_cmd(struct fsl_lpspi_data *fsl_lpspi,
 	u32 temp = 0;
 
 	temp |= fsl_lpspi->config.bpw - 1;
-	temp |= fsl_lpspi->config.prescale << 27;
 	temp |= (fsl_lpspi->config.mode & 0x3) << 30;
-	temp |= (fsl_lpspi->config.chip_select & 0x3) << 24;
-
-	/*
-	 * Set TCR_CONT will keep SS asserted after current transfer.
-	 * For the first transfer, clear TCR_CONTC to assert SS.
-	 * For subsequent transfer, set TCR_CONTC to keep SS asserted.
-	 */
-	temp |= TCR_CONT;
-	if (is_first_xfer)
-		temp &= ~TCR_CONTC;
-	else
-		temp |= TCR_CONTC;
-
+	if (!fsl_lpspi->is_slave) {
+		temp |= fsl_lpspi->config.prescale << 27;
+		temp |= (fsl_lpspi->config.chip_select & 0x3) << 24;
+
+		/*
+		 * Set TCR_CONT will keep SS asserted after current transfer.
+		 * For the first transfer, clear TCR_CONTC to assert SS.
+		 * For subsequent transfer, set TCR_CONTC to keep SS asserted.
+		 */
+		temp |= TCR_CONT;
+		if (is_first_xfer)
+			temp &= ~TCR_CONTC;
+		else
+			temp |= TCR_CONTC;
+	}
 	writel(temp, fsl_lpspi->base + IMX7ULP_TCR);
 
 	dev_dbg(fsl_lpspi->dev, "TCR=0x%x\n", temp);
@@ -273,13 +278,18 @@ static int fsl_lpspi_config(struct fsl_lpspi_data *fsl_lpspi)
 	writel(temp, fsl_lpspi->base + IMX7ULP_CR);
 	writel(0, fsl_lpspi->base + IMX7ULP_CR);
 
-	ret = fsl_lpspi_set_bitrate(fsl_lpspi);
-	if (ret)
-		return ret;
+	if (!fsl_lpspi->is_slave) {
+		ret = fsl_lpspi_set_bitrate(fsl_lpspi);
+		if (ret)
+			return ret;
+	}
 
 	fsl_lpspi_set_watermark(fsl_lpspi);
 
-	temp = CFGR1_PCSCFG | CFGR1_MASTER;
+	if (!fsl_lpspi->is_slave)
+		temp = CFGR1_MASTER;
+	else
+		temp = CFGR1_PINCFG;
 	if (fsl_lpspi->config.mode & SPI_CS_HIGH)
 		temp |= CFGR1_PCSPOL;
 	writel(temp, fsl_lpspi->base + IMX7ULP_CFGR1);
@@ -322,6 +332,37 @@ static void fsl_lpspi_setup_transfer(struct spi_device *spi,
 	fsl_lpspi_config(fsl_lpspi);
 }
 
+static int fsl_lpspi_slave_abort(struct spi_controller *controller)
+{
+	struct fsl_lpspi_data *fsl_lpspi =
+				spi_controller_get_devdata(controller);
+
+	fsl_lpspi->slave_aborted = true;
+	complete(&fsl_lpspi->xfer_done);
+	return 0;
+}
+
+static int fsl_lpspi_wait_for_completion(struct spi_controller *controller)
+{
+	struct fsl_lpspi_data *fsl_lpspi =
+				spi_controller_get_devdata(controller);
+
+	if (fsl_lpspi->is_slave) {
+		if (wait_for_completion_interruptible(&fsl_lpspi->xfer_done) ||
+			fsl_lpspi->slave_aborted) {
+			dev_dbg(fsl_lpspi->dev, "interrupted\n");
+			return -EINTR;
+		}
+	} else {
+		if (!wait_for_completion_timeout(&fsl_lpspi->xfer_done, HZ)) {
+			dev_dbg(fsl_lpspi->dev, "wait for completion timeout\n");
+			return -ETIMEDOUT;
+		}
+	}
+
+	return 0;
+}
+
 static int fsl_lpspi_transfer_one(struct spi_controller *controller,
 				  struct spi_device *spi,
 				  struct spi_transfer *t)
@@ -335,13 +376,13 @@ static int fsl_lpspi_transfer_one(struct spi_controller *controller,
 	fsl_lpspi->remain = t->len;
 
 	reinit_completion(&fsl_lpspi->xfer_done);
+	fsl_lpspi->slave_aborted = false;
+
 	fsl_lpspi_write_tx_fifo(fsl_lpspi);
 
-	ret = wait_for_completion_timeout(&fsl_lpspi->xfer_done, HZ);
-	if (!ret) {
-		dev_dbg(fsl_lpspi->dev, "wait for completion timeout\n");
-		return -ETIMEDOUT;
-	}
+	ret = fsl_lpspi_wait_for_completion(controller);
+	if (ret)
+		return ret;
 
 	ret = fsl_lpspi_txfifo_empty(fsl_lpspi);
 	if (ret)
@@ -380,10 +421,12 @@ static int fsl_lpspi_transfer_one_msg(struct spi_controller *controller,
 	}
 
 complete:
-	/* de-assert SS, then finalize current message */
-	temp = readl(fsl_lpspi->base + IMX7ULP_TCR);
-	temp &= ~TCR_CONTC;
-	writel(temp, fsl_lpspi->base + IMX7ULP_TCR);
+	if (!fsl_lpspi->is_slave) {
+		/* de-assert SS, then finalize current message */
+		temp = readl(fsl_lpspi->base + IMX7ULP_TCR);
+		temp &= ~TCR_CONTC;
+		writel(temp, fsl_lpspi->base + IMX7ULP_TCR);
+	}
 
 	msg->status = ret;
 	spi_finalize_current_message(controller);
@@ -421,8 +464,13 @@ static int fsl_lpspi_probe(struct platform_device *pdev)
 	int ret, irq;
 	u32 temp;
 
-	controller = spi_alloc_master(&pdev->dev,
+	if (of_property_read_bool((&pdev->dev)->of_node, "spi-slave"))
+		controller = spi_alloc_slave(&pdev->dev,
+					sizeof(struct fsl_lpspi_data));
+	else
+		controller = spi_alloc_master(&pdev->dev,
 					sizeof(struct fsl_lpspi_data));
+
 	if (!controller)
 		return -ENOMEM;
 
@@ -433,6 +481,8 @@ static int fsl_lpspi_probe(struct platform_device *pdev)
 
 	fsl_lpspi = spi_controller_get_devdata(controller);
 	fsl_lpspi->dev = &pdev->dev;
+	fsl_lpspi->is_slave = of_property_read_bool((&pdev->dev)->of_node,
+						    "spi-slave");
 
 	controller->transfer_one_message = fsl_lpspi_transfer_one_msg;
 	controller->prepare_transfer_hardware = lpspi_prepare_xfer_hardware;
@@ -441,6 +491,7 @@ static int fsl_lpspi_probe(struct platform_device *pdev)
 	controller->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
 	controller->dev.of_node = pdev->dev.of_node;
 	controller->bus_num = pdev->id;
+	controller->slave_abort = fsl_lpspi_slave_abort;
 
 	init_completion(&fsl_lpspi->xfer_done);
 
-- 
2.19.0.rc2