spi: Add RZ/V2M CSI target support

Merge series from Fabrizio Castro <fabrizio.castro.jz@renesas.com>:

The CSI IP found inside the Renesas RZ/V2M SoC supports both SPI host
and target.  This series extends the CSI dt-bindings and driver to
add SPI target support.

Documentation/devicetree/bindings/spi/renesas,rzv2m-csi.yaml

@@ -39,6 +39,12 @@ properties:
   power-domains:
     maxItems: 1
 
+  renesas,csi-no-ss:
+    type: boolean
+    description:
+      The CSI Slave Selection (SS) pin won't be used to enable transmission and
+      reception. Only available when in target mode.
+
 required:
   - compatible
   - reg
@@ -50,6 +56,9 @@ required:
   - '#address-cells'
   - '#size-cells'
 
+dependencies:
+  renesas,csi-no-ss: [ spi-slave ]
+
 unevaluatedProperties: false
 
 examples:

drivers/spi/Kconfig

@@ -862,7 +862,8 @@ config SPI_RZV2M_CSI
 	tristate "Renesas RZ/V2M CSI controller"
 	depends on ARCH_RENESAS || COMPILE_TEST
 	help
-	  SPI driver for Renesas RZ/V2M Clocked Serial Interface (CSI)
+	  SPI driver for Renesas RZ/V2M Clocked Serial Interface (CSI).
+	  CSI supports both SPI host and SPI target roles.
 
 config SPI_QCOM_QSPI
 	tristate "QTI QSPI controller"

drivers/spi/spi-rzv2m-csi.c

@@ -11,6 +11,7 @@
 #include <linux/interrupt.h>
 #include <linux/iopoll.h>
 #include <linux/log2.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/reset.h>
@@ -38,6 +39,9 @@
 #define CSI_MODE_SETUP		0x00000040
 
 /* CSI_CLKSEL */
+#define CSI_CLKSEL_SS_ENA	BIT(19)
+#define CSI_CLKSEL_SS_POL	BIT(18)
+#define CSI_CLKSEL_SS		(CSI_CLKSEL_SS_ENA | CSI_CLKSEL_SS_POL)
 #define CSI_CLKSEL_CKP		BIT(17)
 #define CSI_CLKSEL_DAP		BIT(16)
 #define CSI_CLKSEL_MODE		(CSI_CLKSEL_CKP|CSI_CLKSEL_DAP)
@@ -82,6 +86,10 @@
 
 #define CSI_MAX_SPI_SCKO	(8 * HZ_PER_MHZ)
 
+#define CSI_CLKSEL_SS_DISABLED			0
+#define CSI_CLKSEL_SS_ENABLED_ACTIVE_LOW	BIT(1)
+#define CSI_CLKSEL_SS_ENABLED_ACTIVE_HIGH	GENMASK(1, 0)
+
 struct rzv2m_csi_priv {
 	void __iomem *base;
 	struct clk *csiclk;
@@ -99,6 +107,8 @@ struct rzv2m_csi_priv {
 	wait_queue_head_t wait;
 	u32 errors;
 	u32 status;
+	bool target_aborted;
+	bool use_ss_pin;
 };
 
 static void rzv2m_csi_reg_write_bit(const struct rzv2m_csi_priv *csi,
@@ -193,6 +203,14 @@ static int rzv2m_csi_read_rxfifo(struct rzv2m_csi_priv *csi)
 	return 0;
 }
 
+static inline void rzv2m_csi_empty_rxfifo(struct rzv2m_csi_priv *csi)
+{
+	unsigned int i;
+
+	for (i = 0; i < csi->words_to_transfer; i++)
+		readl(csi->base + CSI_IFIFO);
+}
+
 static inline void rzv2m_csi_calc_current_transfer(struct rzv2m_csi_priv *csi)
 {
 	unsigned int bytes_transferred = max(csi->bytes_received, csi->bytes_sent);
@@ -279,32 +297,23 @@ static int rzv2m_csi_wait_for_interrupt(struct rzv2m_csi_priv *csi,
 
 	rzv2m_csi_enable_irqs(csi, enable_bits);
 
-	ret = wait_event_timeout(csi->wait,
-				 ((csi->status & wait_mask) == wait_mask) ||
-				 csi->errors, HZ);
+	if (spi_controller_is_target(csi->controller)) {
+		ret = wait_event_interruptible(csi->wait,
+				((csi->status & wait_mask) == wait_mask) ||
+				csi->errors || csi->target_aborted);
+		if (ret || csi->target_aborted)
+			ret = -EINTR;
+	} else {
+		ret = wait_event_timeout(csi->wait,
+				((csi->status & wait_mask) == wait_mask) ||
+				csi->errors, HZ) == 0 ? -ETIMEDOUT : 0;
+	}
 
 	rzv2m_csi_disable_irqs(csi, enable_bits);
 
 	if (csi->errors)
 		return -EIO;
 
-	if (!ret)
-		return -ETIMEDOUT;
-
-	return 0;
-}
-
-static int rzv2m_csi_wait_for_tx_empty(struct rzv2m_csi_priv *csi)
-{
-	int ret;
-
-	if (readl(csi->base + CSI_OFIFOL) == 0)
-		return 0;
-
-	ret = rzv2m_csi_wait_for_interrupt(csi, CSI_INT_TREND, CSI_CNT_TREND_E);
-	if (ret == -ETIMEDOUT)
-		csi->errors |= TX_TIMEOUT_ERROR;
-
 	return ret;
 }
 
@@ -312,7 +321,7 @@ static inline int rzv2m_csi_wait_for_rx_ready(struct rzv2m_csi_priv *csi)
 {
 	int ret;
 
-	if (readl(csi->base + CSI_IFIFOL) == csi->bytes_to_transfer)
+	if (readl(csi->base + CSI_IFIFOL) >= csi->bytes_to_transfer)
 		return 0;
 
 	ret = rzv2m_csi_wait_for_interrupt(csi, CSI_INT_R_TRGR,
@@ -388,6 +397,7 @@ static void rzv2m_csi_setup_operating_mode(struct rzv2m_csi_priv *csi,
 static int rzv2m_csi_setup(struct spi_device *spi)
 {
 	struct rzv2m_csi_priv *csi = spi_controller_get_devdata(spi->controller);
+	u32 slave_selection = CSI_CLKSEL_SS_DISABLED;
 	int ret;
 
 	rzv2m_csi_sw_reset(csi, 0);
@@ -402,8 +412,17 @@ static int rzv2m_csi_setup(struct spi_device *spi)
 	rzv2m_csi_reg_write_bit(csi, CSI_MODE, CSI_MODE_DIR,
 				!!(spi->mode & SPI_LSB_FIRST));
 
-	/* Set the operation mode as master */
-	rzv2m_csi_reg_write_bit(csi, CSI_CLKSEL, CSI_CLKSEL_SLAVE, 0);
+	/* Set the role, 1 for target and 0 for host */
+	rzv2m_csi_reg_write_bit(csi, CSI_CLKSEL, CSI_CLKSEL_SLAVE,
+				!!spi_controller_is_target(csi->controller));
+
+	if (csi->use_ss_pin)
+		slave_selection = spi->mode & SPI_CS_HIGH ?
+			CSI_CLKSEL_SS_ENABLED_ACTIVE_HIGH :
+			CSI_CLKSEL_SS_ENABLED_ACTIVE_LOW;
+
+	/* Configure the slave selection (SS) pin */
+	rzv2m_csi_reg_write_bit(csi, CSI_CLKSEL, CSI_CLKSEL_SS, slave_selection);
 
 	/* Give the IP a SW reset */
 	ret = rzv2m_csi_sw_reset(csi, 1);
@@ -431,9 +450,13 @@ static int rzv2m_csi_pio_transfer(struct rzv2m_csi_priv *csi)
 	/* Make sure the TX FIFO is empty */
 	writel(0, csi->base + CSI_OFIFOL);
 
+	/* Make sure the RX FIFO is empty */
+	writel(0, csi->base + CSI_IFIFOL);
+
 	csi->bytes_sent = 0;
 	csi->bytes_received = 0;
 	csi->errors = 0;
+	csi->target_aborted = false;
 
 	rzv2m_csi_disable_all_irqs(csi);
 	rzv2m_csi_clear_all_irqs(csi);
@@ -452,28 +475,21 @@ static int rzv2m_csi_pio_transfer(struct rzv2m_csi_priv *csi)
 
 		rzv2m_csi_enable_irqs(csi, CSI_INT_OVERF | CSI_INT_UNDER);
 
-		/* Make sure the RX FIFO is empty */
-		writel(0, csi->base + CSI_IFIFOL);
-
 		writel(readl(csi->base + CSI_INT), csi->base + CSI_INT);
 		csi->status = 0;
 
-		rzv2m_csi_start_stop_operation(csi, 1, false);
-
 		/* TX */
 		if (csi->txbuf) {
 			ret = rzv2m_csi_fill_txfifo(csi);
 			if (ret)
 				break;
 
-			ret = rzv2m_csi_wait_for_tx_empty(csi);
-			if (ret)
-				break;
-
 			if (csi->bytes_sent == csi->buffer_len)
 				tx_completed = true;
 		}
 
+		rzv2m_csi_start_stop_operation(csi, 1, false);
+
 		/*
 		 * Make sure the RX FIFO contains the desired number of words.
 		 * We then either flush its content, or we copy it onto
@@ -483,31 +499,28 @@ static int rzv2m_csi_pio_transfer(struct rzv2m_csi_priv *csi)
 		if (ret)
 			break;
 
-		/* RX */
-		if (csi->rxbuf) {
+		if (!spi_controller_is_target(csi->controller))
 			rzv2m_csi_start_stop_operation(csi, 0, false);
 
+		/* RX */
+		if (csi->rxbuf) {
 			ret = rzv2m_csi_read_rxfifo(csi);
 			if (ret)
 				break;
 
 			if (csi->bytes_received == csi->buffer_len)
 				rx_completed = true;
+		} else {
+			rzv2m_csi_empty_rxfifo(csi);
 		}
 
-		ret = rzv2m_csi_start_stop_operation(csi, 0, true);
-		if (ret)
-			goto pio_quit;
-
 		if (csi->errors) {
 			ret = -EIO;
-			goto pio_quit;
+			break;
 		}
 	}
 
 	rzv2m_csi_start_stop_operation(csi, 0, true);
-
-pio_quit:
 	rzv2m_csi_disable_all_irqs(csi);
 	rzv2m_csi_enable_rx_trigger(csi, false);
 	rzv2m_csi_clear_all_irqs(csi);
@@ -529,7 +542,8 @@ static int rzv2m_csi_transfer_one(struct spi_controller *controller,
 
 	rzv2m_csi_setup_operating_mode(csi, transfer);
 
-	rzv2m_csi_setup_clock(csi, transfer->speed_hz);
+	if (!spi_controller_is_target(csi->controller))
+		rzv2m_csi_setup_clock(csi, transfer->speed_hz);
 
 	ret = rzv2m_csi_pio_transfer(csi);
 	if (ret) {
@@ -546,24 +560,48 @@ static int rzv2m_csi_transfer_one(struct spi_controller *controller,
 	return ret;
 }
 
+static int rzv2m_csi_target_abort(struct spi_controller *ctlr)
+{
+	struct rzv2m_csi_priv *csi = spi_controller_get_devdata(ctlr);
+
+	csi->target_aborted = true;
+	wake_up(&csi->wait);
+
+	return 0;
+}
+
 static int rzv2m_csi_probe(struct platform_device *pdev)
 {
+	struct device_node *np = pdev->dev.of_node;
 	struct spi_controller *controller;
 	struct device *dev = &pdev->dev;
 	struct rzv2m_csi_priv *csi;
 	struct reset_control *rstc;
+	bool target_mode;
 	int irq;
 	int ret;
 
-	controller = devm_spi_alloc_host(dev, sizeof(*csi));
+	target_mode = of_property_read_bool(np, "spi-slave");
+
+	if (target_mode)
+		controller = devm_spi_alloc_target(dev, sizeof(*csi));
+	else
+		controller = devm_spi_alloc_host(dev, sizeof(*csi));
+
 	if (!controller)
 		return -ENOMEM;
 
 	csi = spi_controller_get_devdata(controller);
 	platform_set_drvdata(pdev, csi);
 
+	csi->use_ss_pin = false;
+	if (spi_controller_is_target(controller) &&
+	    !of_property_read_bool(np, "renesas,csi-no-ss"))
+		csi->use_ss_pin = true;
+
 	csi->dev = dev;
 	csi->controller = controller;
+	csi->target_aborted = false;
 
 	csi->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(csi->base))
@@ -589,11 +627,12 @@ static int rzv2m_csi_probe(struct platform_device *pdev)
 
 	init_waitqueue_head(&csi->wait);
 
-	controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST;
+	controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_CS_HIGH;
 	controller->bits_per_word_mask = SPI_BPW_MASK(16) | SPI_BPW_MASK(8);
 	controller->setup = rzv2m_csi_setup;
 	controller->transfer_one = rzv2m_csi_transfer_one;
 	controller->use_gpio_descriptors = true;
+	controller->target_abort = rzv2m_csi_target_abort;
 
 	device_set_node(&controller->dev, dev_fwnode(dev));