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Subject[PATCH 2/2] spi: sifive: Add driver for the SiFive SPI controller
Date
Add driver for the SiFive SPI controller
on the HiFive Unleashed board.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Yash Shah <yash.shah@sifive.com>
---
drivers/spi/Kconfig | 6 +
drivers/spi/Makefile | 1 +
drivers/spi/spi-sifive.c | 450 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 457 insertions(+)
create mode 100644 drivers/spi/spi-sifive.c

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 9f89cb1..f129343 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -631,6 +631,12 @@ config SPI_SH_HSPI
help
SPI driver for SuperH HSPI blocks.

+config SPI_SIFIVE
+ tristate "SiFive SPI controller"
+ depends on HAS_IOMEM
+ help
+ This exposes the SPI controller IP from SiFive.
+
config SPI_SIRF
tristate "CSR SiRFprimaII SPI controller"
depends on SIRF_DMA
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index f296270..7afdc97 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -93,6 +93,7 @@ obj-$(CONFIG_SPI_SH) += spi-sh.o
obj-$(CONFIG_SPI_SH_HSPI) += spi-sh-hspi.o
obj-$(CONFIG_SPI_SH_MSIOF) += spi-sh-msiof.o
obj-$(CONFIG_SPI_SH_SCI) += spi-sh-sci.o
+obj-$(CONFIG_SPI_SIFIVE) += spi-sifive.o
obj-$(CONFIG_SPI_SIRF) += spi-sirf.o
obj-$(CONFIG_SPI_SLAVE_MT27XX) += spi-slave-mt27xx.o
obj-$(CONFIG_SPI_SPRD) += spi-sprd.o
diff --git a/drivers/spi/spi-sifive.c b/drivers/spi/spi-sifive.c
new file mode 100644
index 0000000..961307c
--- /dev/null
+++ b/drivers/spi/spi-sifive.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright 2018 SiFive, Inc.
+//
+// SiFive SPI controller driver (master mode only)
+//
+// Author: SiFive, Inc.
+// sifive@sifive.com
+
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+#include <linux/io.h>
+#include <linux/log2.h>
+
+#define SIFIVE_SPI_DRIVER_NAME "sifive_spi"
+
+#define SIFIVE_SPI_MAX_CS 32
+#define SIFIVE_SPI_DEFAULT_DEPTH 8
+#define SIFIVE_SPI_DEFAULT_MAX_BITS 8
+
+/* register offsets */
+#define SIFIVE_SPI_REG_SCKDIV 0x00 /* Serial clock divisor */
+#define SIFIVE_SPI_REG_SCKMODE 0x04 /* Serial clock mode */
+#define SIFIVE_SPI_REG_CSID 0x10 /* Chip select ID */
+#define SIFIVE_SPI_REG_CSDEF 0x14 /* Chip select default */
+#define SIFIVE_SPI_REG_CSMODE 0x18 /* Chip select mode */
+#define SIFIVE_SPI_REG_DELAY0 0x28 /* Delay control 0 */
+#define SIFIVE_SPI_REG_DELAY1 0x2c /* Delay control 1 */
+#define SIFIVE_SPI_REG_FMT 0x40 /* Frame format */
+#define SIFIVE_SPI_REG_TXDATA 0x48 /* Tx FIFO data */
+#define SIFIVE_SPI_REG_RXDATA 0x4c /* Rx FIFO data */
+#define SIFIVE_SPI_REG_TXMARK 0x50 /* Tx FIFO watermark */
+#define SIFIVE_SPI_REG_RXMARK 0x54 /* Rx FIFO watermark */
+#define SIFIVE_SPI_REG_FCTRL 0x60 /* SPI flash interface control */
+#define SIFIVE_SPI_REG_FFMT 0x64 /* SPI flash instruction format */
+#define SIFIVE_SPI_REG_IE 0x70 /* Interrupt Enable Register */
+#define SIFIVE_SPI_REG_IP 0x74 /* Interrupt Pendings Register */
+
+/* sckdiv bits */
+#define SIFIVE_SPI_SCKDIV_DIV_MASK 0xfffU
+
+/* sckmode bits */
+#define SIFIVE_SPI_SCKMODE_PHA BIT(0)
+#define SIFIVE_SPI_SCKMODE_POL BIT(1)
+#define SIFIVE_SPI_SCKMODE_MODE_MASK (SIFIVE_SPI_SCKMODE_PHA | \
+ SIFIVE_SPI_SCKMODE_POL)
+
+/* csmode bits */
+#define SIFIVE_SPI_CSMODE_MODE_AUTO 0U
+#define SIFIVE_SPI_CSMODE_MODE_HOLD 2U
+#define SIFIVE_SPI_CSMODE_MODE_OFF 3U
+
+/* delay0 bits */
+#define SIFIVE_SPI_DELAY0_CSSCK(x) ((u32)(x))
+#define SIFIVE_SPI_DELAY0_CSSCK_MASK 0xffU
+#define SIFIVE_SPI_DELAY0_SCKCS(x) ((u32)(x) << 16)
+#define SIFIVE_SPI_DELAY0_SCKCS_MASK (0xffU << 16)
+
+/* delay1 bits */
+#define SIFIVE_SPI_DELAY1_INTERCS(x) ((u32)(x))
+#define SIFIVE_SPI_DELAY1_INTERCS_MASK 0xffU
+#define SIFIVE_SPI_DELAY1_INTERXFR(x) ((u32)(x) << 16)
+#define SIFIVE_SPI_DELAY1_INTERXFR_MASK (0xffU << 16)
+
+/* fmt bits */
+#define SIFIVE_SPI_FMT_PROTO_SINGLE 0U
+#define SIFIVE_SPI_FMT_PROTO_DUAL 1U
+#define SIFIVE_SPI_FMT_PROTO_QUAD 2U
+#define SIFIVE_SPI_FMT_PROTO_MASK 3U
+#define SIFIVE_SPI_FMT_ENDIAN BIT(2)
+#define SIFIVE_SPI_FMT_DIR BIT(3)
+#define SIFIVE_SPI_FMT_LEN(x) ((u32)(x) << 16)
+#define SIFIVE_SPI_FMT_LEN_MASK (0xfU << 16)
+
+/* txdata bits */
+#define SIFIVE_SPI_TXDATA_DATA_MASK 0xffU
+#define SIFIVE_SPI_TXDATA_FULL BIT(31)
+
+/* rxdata bits */
+#define SIFIVE_SPI_RXDATA_DATA_MASK 0xffU
+#define SIFIVE_SPI_RXDATA_EMPTY BIT(31)
+
+/* ie and ip bits */
+#define SIFIVE_SPI_IP_TXWM BIT(0)
+#define SIFIVE_SPI_IP_RXWM BIT(1)
+
+struct sifive_spi {
+ void __iomem *regs; /* virt. address of control registers */
+ struct clk *clk; /* bus clock */
+ unsigned int fifo_depth; /* fifo depth in words */
+ u32 cs_inactive; /* level of the CS pins when inactive */
+ struct completion done; /* wake-up from interrupt */
+};
+
+static void sifive_spi_write(struct sifive_spi *spi, int offset, u32 value)
+{
+ iowrite32(value, spi->regs + offset);
+}
+
+static u32 sifive_spi_read(struct sifive_spi *spi, int offset)
+{
+ return ioread32(spi->regs + offset);
+}
+
+static void sifive_spi_init(struct sifive_spi *spi)
+{
+ /* Watermark interrupts are disabled by default */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
+
+ /* Default watermark FIFO threshold values */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_TXMARK, 1);
+ sifive_spi_write(spi, SIFIVE_SPI_REG_RXMARK, 0);
+
+ /* Set CS/SCK Delays and Inactive Time to defaults */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_DELAY0,
+ SIFIVE_SPI_DELAY0_CSSCK(1) |
+ SIFIVE_SPI_DELAY0_SCKCS(1));
+ sifive_spi_write(spi, SIFIVE_SPI_REG_DELAY1,
+ SIFIVE_SPI_DELAY1_INTERCS(1) |
+ SIFIVE_SPI_DELAY1_INTERXFR(0));
+
+ /* Exit specialized memory-mapped SPI flash mode */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_FCTRL, 0);
+}
+
+static int
+sifive_spi_prepare_message(struct spi_master *master, struct spi_message *msg)
+{
+ struct sifive_spi *spi = spi_master_get_devdata(master);
+ struct spi_device *device = msg->spi;
+
+ /* Update the chip select polarity */
+ if (device->mode & SPI_CS_HIGH)
+ spi->cs_inactive &= ~BIT(device->chip_select);
+ else
+ spi->cs_inactive |= BIT(device->chip_select);
+ sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, spi->cs_inactive);
+
+ /* Select the correct device */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_CSID, device->chip_select);
+
+ /* Set clock mode */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_SCKMODE,
+ device->mode & SIFIVE_SPI_SCKMODE_MODE_MASK);
+
+ return 0;
+}
+
+static void sifive_spi_set_cs(struct spi_device *device, bool is_high)
+{
+ struct sifive_spi *spi = spi_master_get_devdata(device->master);
+
+ /* Reverse polarity is handled by SCMR/CPOL. Not inverted CS. */
+ if (device->mode & SPI_CS_HIGH)
+ is_high = !is_high;
+
+ sifive_spi_write(spi, SIFIVE_SPI_REG_CSMODE, is_high ?
+ SIFIVE_SPI_CSMODE_MODE_AUTO :
+ SIFIVE_SPI_CSMODE_MODE_HOLD);
+}
+
+static int
+sifive_spi_prep_transfer(struct sifive_spi *spi, struct spi_device *device,
+ struct spi_transfer *t)
+{
+ u32 cr;
+ unsigned int mode;
+
+ /* Calculate and program the clock rate */
+ cr = DIV_ROUND_UP(clk_get_rate(spi->clk) >> 1, t->speed_hz) - 1;
+ cr &= SIFIVE_SPI_SCKDIV_DIV_MASK;
+ sifive_spi_write(spi, SIFIVE_SPI_REG_SCKDIV, cr);
+
+ mode = max_t(unsigned int, t->rx_nbits, t->tx_nbits);
+
+ /* Set frame format */
+ cr = SIFIVE_SPI_FMT_LEN(t->bits_per_word);
+ switch (mode) {
+ case SPI_NBITS_QUAD:
+ cr |= SIFIVE_SPI_FMT_PROTO_QUAD;
+ break;
+ case SPI_NBITS_DUAL:
+ cr |= SIFIVE_SPI_FMT_PROTO_DUAL;
+ break;
+ default:
+ cr |= SIFIVE_SPI_FMT_PROTO_SINGLE;
+ break;
+ }
+ if (device->mode & SPI_LSB_FIRST)
+ cr |= SIFIVE_SPI_FMT_ENDIAN;
+ if (!t->rx_buf)
+ cr |= SIFIVE_SPI_FMT_DIR;
+ sifive_spi_write(spi, SIFIVE_SPI_REG_FMT, cr);
+
+ /* We will want to poll if the time we need to wait is
+ * less than the context switching time.
+ * Let's call that threshold 5us. The operation will take:
+ * (8/mode) * fifo_depth / hz <= 5 * 10^-6
+ * 1600000 * fifo_depth <= hz * mode
+ */
+ return 1600000 * spi->fifo_depth <= t->speed_hz * mode;
+}
+
+static irqreturn_t sifive_spi_irq(int irq, void *dev_id)
+{
+ struct sifive_spi *spi = dev_id;
+ u32 ip = sifive_spi_read(spi, SIFIVE_SPI_REG_IP);
+
+ if (ip & (SIFIVE_SPI_IP_TXWM | SIFIVE_SPI_IP_RXWM)) {
+ /* Disable interrupts until next transfer */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
+ complete(&spi->done);
+ return IRQ_HANDLED;
+ }
+
+ return IRQ_NONE;
+}
+
+static void sifive_spi_wait(struct sifive_spi *spi, u32 bit, int poll)
+{
+ if (poll) {
+ u32 cr;
+
+ do {
+ cr = sifive_spi_read(spi, SIFIVE_SPI_REG_IP);
+ } while (!(cr & bit));
+ } else {
+ reinit_completion(&spi->done);
+ sifive_spi_write(spi, SIFIVE_SPI_REG_IE, bit);
+ wait_for_completion(&spi->done);
+ }
+}
+
+static void sifive_spi_tx(struct sifive_spi *spi, const u8 *tx_ptr)
+{
+ WARN_ON_ONCE((sifive_spi_read(spi, SIFIVE_SPI_REG_TXDATA)
+ & SIFIVE_SPI_TXDATA_FULL) != 0);
+ sifive_spi_write(spi, SIFIVE_SPI_REG_TXDATA,
+ *tx_ptr & SIFIVE_SPI_TXDATA_DATA_MASK);
+}
+
+static void sifive_spi_rx(struct sifive_spi *spi, u8 *rx_ptr)
+{
+ u32 data = sifive_spi_read(spi, SIFIVE_SPI_REG_RXDATA);
+
+ WARN_ON_ONCE((data & SIFIVE_SPI_RXDATA_EMPTY) != 0);
+ *rx_ptr = data & SIFIVE_SPI_RXDATA_DATA_MASK;
+}
+
+static int
+sifive_spi_transfer_one(struct spi_master *master, struct spi_device *device,
+ struct spi_transfer *t)
+{
+ struct sifive_spi *spi = spi_master_get_devdata(master);
+ int poll = sifive_spi_prep_transfer(spi, device, t);
+ const u8 *tx_ptr = t->tx_buf;
+ u8 *rx_ptr = t->rx_buf;
+ unsigned int remaining_words = t->len;
+
+ while (remaining_words) {
+ unsigned int n_words = min(remaining_words, spi->fifo_depth);
+ unsigned int i;
+
+ /* Enqueue n_words for transmission */
+ for (i = 0; i < n_words; i++)
+ sifive_spi_tx(spi, tx_ptr++);
+
+ if (rx_ptr) {
+ /* Wait for transmission + reception to complete */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_RXMARK,
+ n_words - 1);
+ sifive_spi_wait(spi, SIFIVE_SPI_IP_RXWM, poll);
+
+ /* Read out all the data from the RX FIFO */
+ for (i = 0; i < n_words; i++)
+ sifive_spi_rx(spi, rx_ptr++);
+ } else {
+ /* Wait for transmission to complete */
+ sifive_spi_wait(spi, SIFIVE_SPI_IP_TXWM, poll);
+ }
+
+ remaining_words -= n_words;
+ }
+
+ return 0;
+}
+
+static int sifive_spi_probe(struct platform_device *pdev)
+{
+ struct sifive_spi *spi;
+ struct resource *res;
+ int ret, irq, num_cs;
+ u32 cs_bits, max_bits_per_word;
+ struct spi_master *master;
+
+ master = spi_alloc_master(&pdev->dev, sizeof(struct sifive_spi));
+ if (!master) {
+ dev_err(&pdev->dev, "out of memory\n");
+ return -ENOMEM;
+ }
+
+ spi = spi_master_get_devdata(master);
+ init_completion(&spi->done);
+ platform_set_drvdata(pdev, master);
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ spi->regs = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(spi->regs)) {
+ dev_err(&pdev->dev, "Unable to map IO resources\n");
+ ret = PTR_ERR(spi->regs);
+ goto put_master;
+ }
+
+ spi->clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(spi->clk)) {
+ dev_err(&pdev->dev, "Unable to find bus clock\n");
+ ret = PTR_ERR(spi->clk);
+ goto put_master;
+ }
+
+ irq = platform_get_irq(pdev, 0);
+ if (irq < 0) {
+ dev_err(&pdev->dev, "Unable to find interrupt\n");
+ ret = irq;
+ goto put_master;
+ }
+
+ /* Optional parameters */
+ ret =
+ of_property_read_u32(pdev->dev.of_node, "sifive,fifo-depth",
+ &spi->fifo_depth);
+ if (ret < 0)
+ spi->fifo_depth = SIFIVE_SPI_DEFAULT_DEPTH;
+
+ ret =
+ of_property_read_u32(pdev->dev.of_node, "sifive,max-bits-per-word",
+ &max_bits_per_word);
+
+ if (!ret && max_bits_per_word < 8) {
+ dev_err(&pdev->dev, "Only 8bit SPI words supported by the driver\n");
+ ret = -EINVAL;
+ goto put_master;
+ }
+
+ /* Spin up the bus clock before hitting registers */
+ ret = clk_prepare_enable(spi->clk);
+ if (ret) {
+ dev_err(&pdev->dev, "Unable to enable bus clock\n");
+ goto put_master;
+ }
+
+ /* probe the number of CS lines */
+ spi->cs_inactive = sifive_spi_read(spi, SIFIVE_SPI_REG_CSDEF);
+ sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, 0xffffffffU);
+ cs_bits = sifive_spi_read(spi, SIFIVE_SPI_REG_CSDEF);
+ sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, spi->cs_inactive);
+ if (!cs_bits) {
+ dev_err(&pdev->dev, "Could not auto probe CS lines\n");
+ ret = -EINVAL;
+ goto put_master;
+ }
+
+ num_cs = ilog2(cs_bits) + 1;
+ if (num_cs > SIFIVE_SPI_MAX_CS) {
+ dev_err(&pdev->dev, "Invalid number of spi slaves\n");
+ ret = -EINVAL;
+ goto put_master;
+ }
+
+ /* Define our master */
+ master->dev.of_node = pdev->dev.of_node;
+ master->bus_num = pdev->id;
+ master->num_chipselect = num_cs;
+ master->mode_bits = SPI_CPHA | SPI_CPOL
+ | SPI_CS_HIGH | SPI_LSB_FIRST
+ | SPI_TX_DUAL | SPI_TX_QUAD
+ | SPI_RX_DUAL | SPI_RX_QUAD;
+ /* TODO: add driver support for bits_per_word < 8
+ * we need to "left-align" the bits (unless SPI_LSB_FIRST)
+ */
+ master->bits_per_word_mask = SPI_BPW_MASK(8);
+ master->flags = SPI_CONTROLLER_MUST_TX | SPI_MASTER_GPIO_SS;
+ master->prepare_message = sifive_spi_prepare_message;
+ master->set_cs = sifive_spi_set_cs;
+ master->transfer_one = sifive_spi_transfer_one;
+
+ pdev->dev.dma_mask = NULL;
+ /* Configure the SPI master hardware */
+ sifive_spi_init(spi);
+
+ /* Register for SPI Interrupt */
+ ret = devm_request_irq(&pdev->dev, irq, sifive_spi_irq, 0,
+ dev_name(&pdev->dev), spi);
+ if (ret) {
+ dev_err(&pdev->dev, "Unable to bind to interrupt\n");
+ goto put_master;
+ }
+
+ dev_info(&pdev->dev, "mapped; irq=%d, cs=%d\n",
+ irq, master->num_chipselect);
+
+ ret = devm_spi_register_master(&pdev->dev, master);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "spi_register_master failed\n");
+ goto put_master;
+ }
+
+ return 0;
+
+put_master:
+ spi_master_put(master);
+
+ return ret;
+}
+
+static int sifive_spi_remove(struct platform_device *pdev)
+{
+ struct spi_master *master = platform_get_drvdata(pdev);
+ struct sifive_spi *spi = spi_master_get_devdata(master);
+
+ /* Disable all the interrupts just in case */
+ sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
+ spi_master_put(master);
+
+ return 0;
+}
+
+static const struct of_device_id sifive_spi_of_match[] = {
+ { .compatible = "sifive,spi0", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, sifive_spi_of_match);
+
+static struct platform_driver sifive_spi_driver = {
+ .probe = sifive_spi_probe,
+ .remove = sifive_spi_remove,
+ .driver = {
+ .name = SIFIVE_SPI_DRIVER_NAME,
+ .of_match_table = sifive_spi_of_match,
+ },
+};
+module_platform_driver(sifive_spi_driver);
+
+MODULE_AUTHOR("SiFive, Inc. <sifive@sifive.com>");
+MODULE_DESCRIPTION("SiFive SPI driver");
+MODULE_LICENSE("GPL");
--
1.9.1
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