spi: Add Meson SPICC driver

The SPICC hardware block on the Amlogic SoCs is Communication oriented and
can do Full-Duplex 8- to 32-bit width SPI transfers up to 30MHz.

The current driver only supportd the PIO transfer mode since the DMA seems
broken on available hardware.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 619 insertions, 0 deletions

diff --git a/drivers/spi/spi-meson-spicc.c b/drivers/spi/spi-meson-spicc.c
new file mode 100644
index 000000000000..7f8429635502
--- /dev/null
+++ b/drivers/spi/spi-meson-spicc.c
@@ -0,0 +1,619 @@
+/*
+ * Driver for Amlogic Meson SPI communication controller (SPICC)
+ *
+ * Copyright (C) BayLibre, SAS
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+#include <linux/types.h>
+#include <linux/interrupt.h>
+#include <linux/reset.h>
+#include <linux/gpio.h>
+
+/*
+ * The Meson SPICC controller could support DMA based transfers, but is not
+ * implemented by the vendor code, and while having the registers documentation
+ * it has never worked on the GXL Hardware.
+ * The PIO mode is the only mode implemented, and due to badly designed HW :
+ * - all transfers are cutted in 16 words burst because the FIFO hangs on
+ *   TX underflow, and there is no TX "Half-Empty" interrupt, so we go by
+ *   FIFO max size chunk only
+ * - CS management is dumb, and goes UP between every burst, so is really a
+ *   "Data Valid" signal than a Chip Select, GPIO link should be used instead
+ *   to have a CS go down over the full transfer
+ */
+
+#define SPICC_MAX_FREQ	30000000
+#define SPICC_MAX_BURST	128
+
+/* Register Map */
+#define SPICC_RXDATA	0x00
+
+#define SPICC_TXDATA	0x04
+
+#define SPICC_CONREG	0x08
+#define SPICC_ENABLE		BIT(0)
+#define SPICC_MODE_MASTER	BIT(1)
+#define SPICC_XCH		BIT(2)
+#define SPICC_SMC		BIT(3)
+#define SPICC_POL		BIT(4)
+#define SPICC_PHA		BIT(5)
+#define SPICC_SSCTL		BIT(6)
+#define SPICC_SSPOL		BIT(7)
+#define SPICC_DRCTL_MASK	GENMASK(9, 8)
+#define SPICC_DRCTL_IGNORE	0
+#define SPICC_DRCTL_FALLING	1
+#define SPICC_DRCTL_LOWLEVEL	2
+#define SPICC_CS_MASK		GENMASK(13, 12)
+#define SPICC_DATARATE_MASK	GENMASK(18, 16)
+#define SPICC_DATARATE_DIV4	0
+#define SPICC_DATARATE_DIV8	1
+#define SPICC_DATARATE_DIV16	2
+#define SPICC_DATARATE_DIV32	3
+#define SPICC_BITLENGTH_MASK	GENMASK(24, 19)
+#define SPICC_BURSTLENGTH_MASK	GENMASK(31, 25)
+
+#define SPICC_INTREG	0x0c
+#define SPICC_TE_EN	BIT(0) /* TX FIFO Empty Interrupt */
+#define SPICC_TH_EN	BIT(1) /* TX FIFO Half-Full Interrupt */
+#define SPICC_TF_EN	BIT(2) /* TX FIFO Full Interrupt */
+#define SPICC_RR_EN	BIT(3) /* RX FIFO Ready Interrupt */
+#define SPICC_RH_EN	BIT(4) /* RX FIFO Half-Full Interrupt */
+#define SPICC_RF_EN	BIT(5) /* RX FIFO Full Interrupt */
+#define SPICC_RO_EN	BIT(6) /* RX FIFO Overflow Interrupt */
+#define SPICC_TC_EN	BIT(7) /* Transfert Complete Interrupt */
+
+#define SPICC_DMAREG	0x10
+#define SPICC_DMA_ENABLE		BIT(0)
+#define SPICC_TXFIFO_THRESHOLD_MASK	GENMASK(5, 1)
+#define SPICC_RXFIFO_THRESHOLD_MASK	GENMASK(10, 6)
+#define SPICC_READ_BURST_MASK		GENMASK(14, 11)
+#define SPICC_WRITE_BURST_MASK		GENMASK(18, 15)
+#define SPICC_DMA_URGENT		BIT(19)
+#define SPICC_DMA_THREADID_MASK		GENMASK(25, 20)
+#define SPICC_DMA_BURSTNUM_MASK		GENMASK(31, 26)
+
+#define SPICC_STATREG	0x14
+#define SPICC_TE	BIT(0) /* TX FIFO Empty Interrupt */
+#define SPICC_TH	BIT(1) /* TX FIFO Half-Full Interrupt */
+#define SPICC_TF	BIT(2) /* TX FIFO Full Interrupt */
+#define SPICC_RR	BIT(3) /* RX FIFO Ready Interrupt */
+#define SPICC_RH	BIT(4) /* RX FIFO Half-Full Interrupt */
+#define SPICC_RF	BIT(5) /* RX FIFO Full Interrupt */
+#define SPICC_RO	BIT(6) /* RX FIFO Overflow Interrupt */
+#define SPICC_TC	BIT(7) /* Transfert Complete Interrupt */
+
+#define SPICC_PERIODREG	0x18
+#define SPICC_PERIOD	GENMASK(14, 0)	/* Wait cycles */
+
+#define SPICC_TESTREG	0x1c
+#define SPICC_TXCNT_MASK	GENMASK(4, 0)	/* TX FIFO Counter */
+#define SPICC_RXCNT_MASK	GENMASK(9, 5)	/* RX FIFO Counter */
+#define SPICC_SMSTATUS_MASK	GENMASK(12, 10)	/* State Machine Status */
+#define SPICC_LBC_RO		BIT(13)	/* Loop Back Control Read-Only */
+#define SPICC_LBC_W1		BIT(14) /* Loop Back Control Write-Only */
+#define SPICC_SWAP_RO		BIT(14) /* RX FIFO Data Swap Read-Only */
+#define SPICC_SWAP_W1		BIT(15) /* RX FIFO Data Swap Write-Only */
+#define SPICC_DLYCTL_RO_MASK	GENMASK(20, 15) /* Delay Control Read-Only */
+#define SPICC_DLYCTL_W1_MASK	GENMASK(21, 16) /* Delay Control Write-Only */
+#define SPICC_FIFORST_RO_MASK	GENMASK(22, 21) /* FIFO Softreset Read-Only */
+#define SPICC_FIFORST_W1_MASK	GENMASK(23, 22) /* FIFO Softreset Write-Only */
+
+#define SPICC_DRADDR	0x20	/* Read Address of DMA */
+
+#define SPICC_DWADDR	0x24	/* Write Address of DMA */
+
+#define writel_bits_relaxed(mask, val, addr) \
+	writel_relaxed((readl_relaxed(addr) & ~(mask)) | (val), addr)
+
+#define SPICC_BURST_MAX	16
+#define SPICC_FIFO_HALF 10
+
+struct meson_spicc_device {
+	struct spi_master		*master;
+	struct platform_device		*pdev;
+	void __iomem			*base;
+	struct clk			*core;
+	struct spi_message		*message;
+	struct spi_transfer		*xfer;
+	u8				*tx_buf;
+	u8				*rx_buf;
+	unsigned int			bytes_per_word;
+	unsigned long			tx_remain;
+	unsigned long			txb_remain;
+	unsigned long			rx_remain;
+	unsigned long			rxb_remain;
+	unsigned long			xfer_remain;
+	bool				is_burst_end;
+	bool				is_last_burst;
+};
+
+static inline bool meson_spicc_txfull(struct meson_spicc_device *spicc)
+{
+	return !!FIELD_GET(SPICC_TF,
+			   readl_relaxed(spicc->base + SPICC_STATREG));
+}
+
+static inline bool meson_spicc_rxready(struct meson_spicc_device *spicc)
+{
+	return FIELD_GET(SPICC_RH | SPICC_RR | SPICC_RF_EN,
+			 readl_relaxed(spicc->base + SPICC_STATREG));
+}
+
+static inline u32 meson_spicc_pull_data(struct meson_spicc_device *spicc)
+{
+	unsigned int bytes = spicc->bytes_per_word;
+	unsigned int byte_shift = 0;
+	u32 data = 0;
+	u8 byte;
+
+	while (bytes--) {
+		byte = *spicc->tx_buf++;
+		data |= (byte & 0xff) << byte_shift;
+		byte_shift += 8;
+	}
+
+	spicc->tx_remain--;
+	return data;
+}
+
+static inline void meson_spicc_push_data(struct meson_spicc_device *spicc,
+					 u32 data)
+{
+	unsigned int bytes = spicc->bytes_per_word;
+	unsigned int byte_shift = 0;
+	u8 byte;
+
+	while (bytes--) {
+		byte = (data >> byte_shift) & 0xff;
+		*spicc->rx_buf++ = byte;
+		byte_shift += 8;
+	}
+
+	spicc->rx_remain--;
+}
+
+static inline void meson_spicc_rx(struct meson_spicc_device *spicc)
+{
+	/* Empty RX FIFO */
+	while (spicc->rx_remain &&
+	       meson_spicc_rxready(spicc))
+		meson_spicc_push_data(spicc,
+				readl_relaxed(spicc->base + SPICC_RXDATA));
+}
+
+static inline void meson_spicc_tx(struct meson_spicc_device *spicc)
+{
+	/* Fill Up TX FIFO */
+	while (spicc->tx_remain &&
+	       !meson_spicc_txfull(spicc))
+		writel_relaxed(meson_spicc_pull_data(spicc),
+			       spicc->base + SPICC_TXDATA);
+}
+
+static inline u32 meson_spicc_setup_rx_irq(struct meson_spicc_device *spicc,
+					   u32 irq_ctrl)
+{
+	if (spicc->rx_remain > SPICC_FIFO_HALF)
+		irq_ctrl |= SPICC_RH_EN;
+	else
+		irq_ctrl |= SPICC_RR_EN;
+
+	return irq_ctrl;
+}
+
+static inline void meson_spicc_setup_burst(struct meson_spicc_device *spicc,
+					   unsigned int burst_len)
+{
+	/* Setup Xfer variables */
+	spicc->tx_remain = burst_len;
+	spicc->rx_remain = burst_len;
+	spicc->xfer_remain -= burst_len * spicc->bytes_per_word;
+	spicc->is_burst_end = false;
+	if (burst_len < SPICC_BURST_MAX || !spicc->xfer_remain)
+		spicc->is_last_burst = true;
+	else
+		spicc->is_last_burst = false;
+
+	/* Setup burst length */
+	writel_bits_relaxed(SPICC_BURSTLENGTH_MASK,
+			FIELD_PREP(SPICC_BURSTLENGTH_MASK,
+				burst_len),
+			spicc->base + SPICC_CONREG);
+
+	/* Fill TX FIFO */
+	meson_spicc_tx(spicc);
+}
+
+static irqreturn_t meson_spicc_irq(int irq, void *data)
+{
+	struct meson_spicc_device *spicc = (void *) data;
+	u32 ctrl = readl_relaxed(spicc->base + SPICC_INTREG);
+	u32 stat = readl_relaxed(spicc->base + SPICC_STATREG) & ctrl;
+
+	ctrl &= ~(SPICC_RH_EN | SPICC_RR_EN);
+
+	/* Empty RX FIFO */
+	meson_spicc_rx(spicc);
+
+	/* Enable TC interrupt since we transferred everything */
+	if (!spicc->tx_remain && !spicc->rx_remain) {
+		spicc->is_burst_end = true;
+
+		/* Enable TC interrupt */
+		ctrl |= SPICC_TC_EN;
+
+		/* Reload IRQ status */
+		stat = readl_relaxed(spicc->base + SPICC_STATREG) & ctrl;
+	}
+
+	/* Check transfer complete */
+	if ((stat & SPICC_TC) && spicc->is_burst_end) {
+		unsigned int burst_len;
+
+		/* Clear TC bit */
+		writel_relaxed(SPICC_TC, spicc->base + SPICC_STATREG);
+
+		/* Disable TC interrupt */
+		ctrl &= ~SPICC_TC_EN;
+
+		if (spicc->is_last_burst) {
+			/* Disable all IRQs */
+			writel(0, spicc->base + SPICC_INTREG);
+
+			spi_finalize_current_transfer(spicc->master);
+
+			return IRQ_HANDLED;
+		}
+
+		burst_len = min_t(unsigned int,
+				  spicc->xfer_remain / spicc->bytes_per_word,
+				  SPICC_BURST_MAX);
+
+		/* Setup burst */
+		meson_spicc_setup_burst(spicc, burst_len);
+
+		/* Restart burst */
+		writel_bits_relaxed(SPICC_XCH, SPICC_XCH,
+				    spicc->base + SPICC_CONREG);
+	}
+
+	/* Setup RX interrupt trigger */
+	ctrl = meson_spicc_setup_rx_irq(spicc, ctrl);
+
+	/* Reconfigure interrupts */
+	writel(ctrl, spicc->base + SPICC_INTREG);
+
+	return IRQ_HANDLED;
+}
+
+static u32 meson_spicc_setup_speed(struct meson_spicc_device *spicc, u32 conf,
+				   u32 speed)
+{
+	unsigned long parent, value;
+	unsigned int i, div;
+
+	parent = clk_get_rate(spicc->core);
+
+	/* Find closest inferior/equal possible speed */
+	for (i = 0 ; i < 7 ; ++i) {
+		/* 2^(data_rate+2) */
+		value = parent >> (i + 2);
+
+		if (value <= speed)
+			break;
+	}
+
+	/* If provided speed it lower than max divider, use max divider */
+	if (i > 7) {
+		div = 7;
+		dev_warn_once(&spicc->pdev->dev, "unable to get close to speed %u\n",
+			      speed);
+	} else
+		div = i;
+
+	dev_dbg(&spicc->pdev->dev, "parent %lu, speed %u -> %lu (%u)\n",
+		parent, speed, value, div);
+
+	conf &= ~SPICC_DATARATE_MASK;
+	conf |= FIELD_PREP(SPICC_DATARATE_MASK, div);
+
+	return conf;
+}
+
+static void meson_spicc_setup_xfer(struct meson_spicc_device *spicc,
+				   struct spi_transfer *xfer)
+{
+	u32 conf, conf_orig;
+
+	/* Read original configuration */
+	conf = conf_orig = readl_relaxed(spicc->base + SPICC_CONREG);
+
+	/* Select closest divider */
+	conf = meson_spicc_setup_speed(spicc, conf, xfer->speed_hz);
+
+	/* Setup word width */
+	conf &= ~SPICC_BITLENGTH_MASK;
+	conf |= FIELD_PREP(SPICC_BITLENGTH_MASK,
+			   (spicc->bytes_per_word << 3) - 1);
+
+	/* Ignore if unchanged */
+	if (conf != conf_orig)
+		writel_relaxed(conf, spicc->base + SPICC_CONREG);
+}
+
+static int meson_spicc_transfer_one(struct spi_master *master,
+				    struct spi_device *spi,
+				    struct spi_transfer *xfer)
+{
+	struct meson_spicc_device *spicc = spi_master_get_devdata(master);
+	unsigned int burst_len;
+	u32 irq = 0;
+
+	/* Store current transfer */
+	spicc->xfer = xfer;
+
+	/* Setup transfer parameters */
+	spicc->tx_buf = (u8 *)xfer->tx_buf;
+	spicc->rx_buf = (u8 *)xfer->rx_buf;
+	spicc->xfer_remain = xfer->len;
+
+	/* Pre-calculate word size */
+	spicc->bytes_per_word =
+	   DIV_ROUND_UP(spicc->xfer->bits_per_word, 8);
+
+	/* Setup transfer parameters */
+	meson_spicc_setup_xfer(spicc, xfer);
+
+	burst_len = min_t(unsigned int,
+			  spicc->xfer_remain / spicc->bytes_per_word,
+			  SPICC_BURST_MAX);
+
+	meson_spicc_setup_burst(spicc, burst_len);
+
+	irq = meson_spicc_setup_rx_irq(spicc, irq);
+
+	/* Start burst */
+	writel_bits_relaxed(SPICC_XCH, SPICC_XCH, spicc->base + SPICC_CONREG);
+
+	/* Enable interrupts */
+	writel_relaxed(irq, spicc->base + SPICC_INTREG);
+
+	return 1;
+}
+
+static int meson_spicc_prepare_message(struct spi_master *master,
+				       struct spi_message *message)
+{
+	struct meson_spicc_device *spicc = spi_master_get_devdata(master);
+	struct spi_device *spi = message->spi;
+	u32 conf = 0;
+
+	/* Store current message */
+	spicc->message = message;
+
+	/* Enable Master */
+	conf |= SPICC_ENABLE;
+	conf |= SPICC_MODE_MASTER;
+
+	/* SMC = 0 */
+
+	/* Setup transfer mode */
+	if (spi->mode & SPI_CPOL)
+		conf |= SPICC_POL;
+	else
+		conf &= ~SPICC_POL;
+
+	if (spi->mode & SPI_CPHA)
+		conf |= SPICC_PHA;
+	else
+		conf &= ~SPICC_PHA;
+
+	/* SSCTL = 0 */
+
+	if (spi->mode & SPI_CS_HIGH)
+		conf |= SPICC_SSPOL;
+	else
+		conf &= ~SPICC_SSPOL;
+
+	if (spi->mode & SPI_READY)
+		conf |= FIELD_PREP(SPICC_DRCTL_MASK, SPICC_DRCTL_LOWLEVEL);
+	else
+		conf |= FIELD_PREP(SPICC_DRCTL_MASK, SPICC_DRCTL_IGNORE);
+
+	/* Select CS */
+	conf |= FIELD_PREP(SPICC_CS_MASK, spi->chip_select);
+
+	/* Default Clock rate core/4 */
+
+	/* Default 8bit word */
+	conf |= FIELD_PREP(SPICC_BITLENGTH_MASK, 8 - 1);
+
+	writel_relaxed(conf, spicc->base + SPICC_CONREG);
+
+	/* Setup no wait cycles by default */
+	writel_relaxed(0, spicc->base + SPICC_PERIODREG);
+
+	writel_bits_relaxed(BIT(24), BIT(24), spicc->base + SPICC_TESTREG);
+
+	return 0;
+}
+
+static int meson_spicc_unprepare_transfer(struct spi_master *master)
+{
+	struct meson_spicc_device *spicc = spi_master_get_devdata(master);
+
+	/* Disable all IRQs */
+	writel(0, spicc->base + SPICC_INTREG);
+
+	/* Disable controller */
+	writel_bits_relaxed(SPICC_ENABLE, 0, spicc->base + SPICC_CONREG);
+
+	device_reset_optional(&spicc->pdev->dev);
+
+	return 0;
+}
+
+static int meson_spicc_setup(struct spi_device *spi)
+{
+	int ret = 0;
+
+	if (!spi->controller_state)
+		spi->controller_state = spi_master_get_devdata(spi->master);
+	else if (gpio_is_valid(spi->cs_gpio))
+		goto out_gpio;
+	else if (spi->cs_gpio == -ENOENT)
+		return 0;
+
+	if (gpio_is_valid(spi->cs_gpio)) {
+		ret = gpio_request(spi->cs_gpio, dev_name(&spi->dev));
+		if (ret) {
+			dev_err(&spi->dev, "failed to request cs gpio\n");
+			return ret;
+		}
+	}
+
+out_gpio:
+	ret = gpio_direction_output(spi->cs_gpio,
+			!(spi->mode & SPI_CS_HIGH));
+
+	return ret;
+}
+
+static void meson_spicc_cleanup(struct spi_device *spi)
+{
+	if (gpio_is_valid(spi->cs_gpio))
+		gpio_free(spi->cs_gpio);
+
+	spi->controller_state = NULL;
+}
+
+static int meson_spicc_probe(struct platform_device *pdev)
+{
+	struct spi_master *master;
+	struct meson_spicc_device *spicc;
+	struct resource *res;
+	int ret, irq, rate;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*spicc));
+	if (!master) {
+		dev_err(&pdev->dev, "master allocation failed\n");
+		return -ENOMEM;
+	}
+	spicc = spi_master_get_devdata(master);
+	spicc->master = master;
+
+	spicc->pdev = pdev;
+	platform_set_drvdata(pdev, spicc);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	spicc->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(spicc->base)) {
+		dev_err(&pdev->dev, "io resource mapping failed\n");
+		ret = PTR_ERR(spicc->base);
+		goto out_master;
+	}
+
+	/* Disable all IRQs */
+	writel_relaxed(0, spicc->base + SPICC_INTREG);
+
+	irq = platform_get_irq(pdev, 0);
+	ret = devm_request_irq(&pdev->dev, irq, meson_spicc_irq,
+			       0, NULL, spicc);
+	if (ret) {
+		dev_err(&pdev->dev, "irq request failed\n");
+		goto out_master;
+	}
+
+	spicc->core = devm_clk_get(&pdev->dev, "core");
+	if (IS_ERR(spicc->core)) {
+		dev_err(&pdev->dev, "core clock request failed\n");
+		ret = PTR_ERR(spicc->core);
+		goto out_master;
+	}
+
+	ret = clk_prepare_enable(spicc->core);
+	if (ret) {
+		dev_err(&pdev->dev, "core clock enable failed\n");
+		goto out_master;
+	}
+	rate = clk_get_rate(spicc->core);
+
+	device_reset_optional(&pdev->dev);
+
+	master->num_chipselect = 4;
+	master->dev.of_node = pdev->dev.of_node;
+	master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_CS_HIGH;
+	master->bits_per_word_mask = SPI_BPW_MASK(32) |
+				     SPI_BPW_MASK(24) |
+				     SPI_BPW_MASK(16) |
+				     SPI_BPW_MASK(8);
+	master->flags = (SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX);
+	master->min_speed_hz = rate >> 9;
+	master->setup = meson_spicc_setup;
+	master->cleanup = meson_spicc_cleanup;
+	master->prepare_message = meson_spicc_prepare_message;
+	master->unprepare_transfer_hardware = meson_spicc_unprepare_transfer;
+	master->transfer_one = meson_spicc_transfer_one;
+
+	/* Setup max rate according to the Meson GX datasheet */
+	if ((rate >> 2) > SPICC_MAX_FREQ)
+		master->max_speed_hz = SPICC_MAX_FREQ;
+	else
+		master->max_speed_hz = rate >> 2;
+
+	ret = devm_spi_register_master(&pdev->dev, master);
+	if (!ret)
+		return 0;
+
+	dev_err(&pdev->dev, "spi master registration failed\n");
+
+out_master:
+	spi_master_put(master);
+
+	return ret;
+}
+
+static int meson_spicc_remove(struct platform_device *pdev)
+{
+	struct meson_spicc_device *spicc = platform_get_drvdata(pdev);
+
+	/* Disable SPI */
+	writel(0, spicc->base + SPICC_CONREG);
+
+	clk_disable_unprepare(spicc->core);
+
+	return 0;
+}
+
+static const struct of_device_id meson_spicc_of_match[] = {
+	{ .compatible = "amlogic,meson-gx-spicc", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, meson_spicc_of_match);
+
+static struct platform_driver meson_spicc_driver = {
+	.probe   = meson_spicc_probe,
+	.remove  = meson_spicc_remove,
+	.driver  = {
+		.name = "meson-spicc",
+		.of_match_table = of_match_ptr(meson_spicc_of_match),
+	},
+};
+
+module_platform_driver(meson_spicc_driver);
+
+MODULE_DESCRIPTION("Meson SPI Communication Controller driver");
+MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
+MODULE_LICENSE("GPL");