[RFC PATCH] spi: add driver for the SiFive SPI controller
From: Emil Renner Berthing
Date: Mon Nov 12 2018 - 09:28:03 EST
From: Palmer Dabbelt <palmer@xxxxxxxxxx>
Add driver for the SiFive SPI controller
on the HiFive Unleashed board.
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxx>
Signed-off-by: Emil Renner Berthing <kernel@xxxxxxxx>
---
.../devicetree/bindings/spi/spi-sifive.txt | 29 ++
drivers/spi/Kconfig | 6 +
drivers/spi/Makefile | 1 +
drivers/spi/spi-sifive.c | 442 ++++++++++++++++++
4 files changed, 478 insertions(+)
create mode 100644 Documentation/devicetree/bindings/spi/spi-sifive.txt
create mode 100644 drivers/spi/spi-sifive.c
Hi all,
I know the discussions about the sifive devicetree compatible
strings haven't come to a conclusion, so I'm sending this as
an RFC to get some feedback on the rest of the code.
Compared to the original[1] I've done the following:
- Update register names and bit fields to the ones in the
FU540-C000 documentation.
- Change the optional devicetree property from "sifive,buffer-size"
to "sifive,fifo-depth". The string "fifo-depth" seems to have more
hits in the existing devicetree bindings and is IMHO a little more
descriptive.
- Change the optional devicetree property from "sifive,bits-per-word"
to "sifive,max-bits-per-word". For a long time I wondered why the
SPI word size was a property on the controller and not the device.
This change makes the meaning a little more clear.
- Be honest about only supporting 8bit SPI words in the driver.
Without SPI_LSB_FIRST and bits_per_word < 8 we need some code
to shift the bits in each byte which is not yet there.
- Program the csdef, csid and sckmode registers from prepare_message
rather than transfer_one. This way we only do it once pr. message
rather than every transfer.
- Drop the irq field from driver data. With devm_request_irq we
don't need to remember it after requesting the irq.
- Drop hz = t->speed_hz ? t->speed_hz : device->max_speed_hz;
The SPI framework handles this for us, so we can just always
use t->speed_hz.
- Fix most checkpatch warnings.
[1]: https://github.com/riscv/riscv-linux/commit/801805694740ad0895e21d10b8f124d138beefbb
/Emil
diff --git a/Documentation/devicetree/bindings/spi/spi-sifive.txt b/Documentation/devicetree/bindings/spi/spi-sifive.txt
new file mode 100644
index 000000000000..96339afcc74f
--- /dev/null
+++ b/Documentation/devicetree/bindings/spi/spi-sifive.txt
@@ -0,0 +1,29 @@
+SiFive SPI controller Device Tree Bindings
+------------------------------------------
+
+Required properties:
+- compatible : Should be "sifive,spi0"
+- reg : Physical base address and size of SPI registers map
+ A second (optional) range can indicate memory mapped flash
+- interrupts : Must contain one entry
+- interrupt-parent : Must be core interrupt controller
+- clocks : Must reference the frequency given to the controller
+- #address-cells : Must be '1', indicating which CS to use
+- #size-cells : Must be '0'
+
+Optional properties:
+- sifive,fifo-depth : Depth of hardware queues; defaults to 8
+- sifive,max-bits-per-word : Maximum bits per word; defaults to 8
+
+Example:
+ spi: spi@10040000 {
+ compatible = "sifive,spi0";
+ reg = <0x0 0x10040000 0x0 0x1000 0x0 0x20000000 0x0 0x10000000>;
+ interrupt-parent = <&plic>;
+ interrupts = <51>;
+ clocks = <&tlclk>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+ sifive,fifo-depth = <8>;
+ sifive,max-bits-per-word = <8>;
+ };
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 7d3a5c94727e..50bfadd24c32 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -615,6 +615,12 @@ 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 3575205c5c27..76216f1861df 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -90,6 +90,7 @@ 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 000000000000..8df19d2b8b7f
--- /dev/null
+++ b/drivers/spi/spi-sifive.c
@@ -0,0 +1,442 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SiFive SPI controller driver (master mode only)
+ *
+ * Author: SiFive, Inc.
+ * sifive@xxxxxxxxxx
+ *
+ * Copyright 2018 SiFive, Inc.
+ */
+
+#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>
+
+/* for consistency we need this symbol */
+#ifdef REG_FMT
+#undef REG_FMT
+#endif
+
+#define SIFIVE_SPI_MAX_CS 32
+
+#define SIFIVE_SPI_NAME "sifive_spi"
+
+#define SIFIVE_SPI_DEFAULT_DEPTH 8
+#define SIFIVE_SPI_DEFAULT_BITS 8
+
+/* register offsets */
+#define REG_SCKDIV 0x00 /* Serial clock divisor */
+#define REG_SCKMODE 0x04 /* Serial clock mode */
+#define REG_CSID 0x10 /* Chip select ID */
+#define REG_CSDEF 0x14 /* Chip select default */
+#define REG_CSMODE 0x18 /* Chip select mode */
+#define REG_DELAY0 0x28 /* Delay control 0 */
+#define REG_DELAY1 0x2c /* Delay control 1 */
+#define REG_FMT 0x40 /* Frame format */
+#define REG_TXDATA 0x48 /* Tx FIFO data */
+#define REG_RXDATA 0x4c /* Rx FIFO data */
+#define REG_TXMARK 0x50 /* Tx FIFO watermark */
+#define REG_RXMARK 0x54 /* Rx FIFO watermark */
+#define REG_FCTRL 0x60 /* SPI flash interface control */
+#define REG_FFMT 0x64 /* SPI flash instruction format */
+#define REG_IE 0x70 /* Interrupt Enable Register */
+#define REG_IP 0x74 /* Interrupt Pendings Register */
+
+/* sckdiv bits */
+#define SCKDIV_DIV_MASK 0xfffU
+
+/* sckmode bits */
+#define SCKMODE_PHA (1U << 0)
+#define SCKMODE_POL (1U << 1)
+#define SCKMODE_MODE_MASK (SCKMODE_PHA | SCKMODE_POL)
+
+/* csmode bits */
+#define CSMODE_MODE_AUTO 0U
+#define CSMODE_MODE_HOLD 2U
+#define CSMODE_MODE_OFF 3U
+
+/* delay0 bits */
+#define DELAY0_CSSCK_MASK 0xffU
+#define DELAY0_SCKCS_MASK (0xffU << 16)
+
+/* delay1 bits */
+#define DELAY1_INTERCS_MASK 0xffU
+#define DELAY1_INTERXFR_MASK (0xffU << 16)
+
+/* fmt bits */
+#define FMT_PROTO_SINGLE 0U
+#define FMT_PROTO_DUAL 1U
+#define FMT_PROTO_QUAD 2U
+#define FMT_PROTO_MASK 3U
+#define FMT_ENDIAN (1U << 2)
+#define FMT_DIR (1U << 3)
+#define FMT_LEN(x) ((u32)(x) << 16)
+#define FMT_LEN_MASK (0xfU << 16)
+
+/* txdata bits */
+#define TXDATA_DATA_MASK 0xffU
+#define TXDATA_FULL (1U << 31)
+
+/* rxdata bits */
+#define RXDATA_DATA_MASK 0xffU
+#define RXDATA_EMPTY (1U << 31)
+
+/* ie and ip bits */
+#define IP_TXWM (1U << 0)
+#define IP_RXWM (1U << 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, REG_IE, 0);
+
+ /* Default watermark FIFO threshold values */
+ sifive_spi_write(spi, REG_TXMARK, 1);
+ sifive_spi_write(spi, REG_RXMARK, 0);
+
+ /* Set CS/SCK Delays and Inactive Time to defaults */
+
+ /* Exit specialized memory-mapped SPI flash mode */
+ sifive_spi_write(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, REG_CSDEF, spi->cs_inactive);
+
+ /* Select the correct device */
+ sifive_spi_write(spi, REG_CSID, device->chip_select);
+
+ /* Set clock mode */
+ sifive_spi_write(spi, REG_SCKMODE, device->mode & SCKMODE_MODE_MASK);
+
+ return 0;
+}
+
+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 &= SCKDIV_DIV_MASK;
+ sifive_spi_write(spi, REG_SCKDIV, cr);
+
+ mode = max_t(unsigned int, t->rx_nbits, t->tx_nbits);
+
+ /* Set frame format */
+ cr = FMT_LEN(t->bits_per_word);
+ switch (mode) {
+ case SPI_NBITS_QUAD:
+ cr |= FMT_PROTO_QUAD;
+ break;
+ case SPI_NBITS_DUAL:
+ cr |= FMT_PROTO_DUAL;
+ break;
+ default:
+ cr |= FMT_PROTO_SINGLE;
+ break;
+ }
+ if (device->mode & SPI_LSB_FIRST)
+ cr |= FMT_ENDIAN;
+ if (!t->rx_buf)
+ cr |= FMT_DIR;
+ sifive_spi_write(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 void sifive_spi_tx(struct sifive_spi *spi, const u8 *tx_ptr)
+{
+ WARN_ON_ONCE((sifive_spi_read(spi, REG_TXDATA) & TXDATA_FULL) != 0);
+ sifive_spi_write(spi, REG_TXDATA, *tx_ptr & TXDATA_DATA_MASK);
+}
+
+static void sifive_spi_rx(struct sifive_spi *spi, u8 *rx_ptr)
+{
+ u32 data = sifive_spi_read(spi, REG_RXDATA);
+
+ WARN_ON_ONCE((data & RXDATA_EMPTY) != 0);
+ *rx_ptr = data & RXDATA_DATA_MASK;
+}
+
+static void sifive_spi_wait(struct sifive_spi *spi, u32 bit, int poll)
+{
+ if (poll) {
+ u32 cr;
+ do cr = sifive_spi_read(spi, REG_IP);
+ while (!(cr & bit));
+ } else {
+ reinit_completion(&spi->done);
+ sifive_spi_write(spi, REG_IE, bit);
+ wait_for_completion(&spi->done);
+ }
+}
+
+static void sifive_spi_execute(struct sifive_spi *spi,
+ struct spi_transfer *t, int poll)
+{
+ 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, REG_RXMARK, n_words-1);
+ sifive_spi_wait(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, IP_TXWM, poll);
+ }
+
+ remaining_words -= n_words;
+ }
+}
+
+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);
+
+ sifive_spi_execute(spi, t, poll);
+
+ 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, REG_CSMODE,
+ is_high ? CSMODE_MODE_AUTO : CSMODE_MODE_HOLD);
+}
+
+static irqreturn_t sifive_spi_irq(int irq, void *dev_id)
+{
+ struct sifive_spi *spi = dev_id;
+ u32 ip = sifive_spi_read(spi, REG_IP);
+
+ if (ip & (IP_TXWM | IP_RXWM)) {
+ /* Disable interrupts until next transfer */
+ sifive_spi_write(spi, REG_IE, 0);
+ complete(&spi->done);
+ return IRQ_HANDLED;
+ }
+
+ return IRQ_NONE;
+}
+
+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 are 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, REG_CSDEF);
+ sifive_spi_write(spi, REG_CSDEF, 0xffffffffU);
+ cs_bits = sifive_spi_read(spi, REG_CSDEF);
+ sifive_spi_write(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;
+ 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;
+
+ /* If mmc_spi sees a dma_mask, it starts using dma mapped buffers.
+ * Probably it should rely on the SPI core auto mapping instead.
+ */
+ 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, 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_NAME,
+ .of_match_table = sifive_spi_of_match,
+ },
+};
+module_platform_driver(sifive_spi_driver);
+
+MODULE_AUTHOR("SiFive, Inc. <sifive@xxxxxxxxxx>");
+MODULE_DESCRIPTION("SiFive SPI driver");
+MODULE_LICENSE("GPL");
--
2.19.1