[PATCH v5 2/2] spi: add driver for J-Core SPI controller

Rich Felker
2016-04-03T05:12:45Z

The J-Core "spi2" device is a PIO-based SPI master controller. It
differs from "bitbang" devices in that that it's clocked in hardware
rather than via soft clock modulation over gpio, and performs
byte-at-a-time transfers between the cpu and SPI controller.

This driver will be extended to support future versions of the J-Core
SPI controller with DMA transfers when they become available.

Signed-off-by: Rich Felker <dalias-8zAoT0mYgF4@public.gmane.org>
---
drivers/spi/Kconfig | 7 ++
drivers/spi/Makefile | 1 +
drivers/spi/spi-jcore.c | 232 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 240 insertions(+)
create mode 100644 drivers/spi/spi-jcore.c

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index d6fb8d4..1abb3d7 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -285,6 +285,13 @@ config SPI_IMX
This enables using the Freescale i.MX SPI controllers in master
mode.

+config SPI_JCORE
+ tristate "J-Core SPI Master"
+ depends on OF && (SUPERH || COMPILE_TEST)
+ help
+ This enables support for the SPI master controller in the J-Core
+ synthesizable, open source SoC.
+
config SPI_LM70_LLP
tristate "Parallel port adapter for LM70 eval board (DEVELOPMENT)"
depends on PARPORT
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 185367e..8715fec 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_SPI_FSL_SPI) += spi-fsl-spi.o
obj-$(CONFIG_SPI_GPIO) += spi-gpio.o
obj-$(CONFIG_SPI_IMG_SPFI) += spi-img-spfi.o
obj-$(CONFIG_SPI_IMX) += spi-imx.o
+obj-$(CONFIG_SPI_JCORE) += spi-jcore.o
obj-$(CONFIG_SPI_LM70_LLP) += spi-lm70llp.o
obj-$(CONFIG_SPI_LP8841_RTC) += spi-lp8841-rtc.o
obj-$(CONFIG_SPI_MESON_SPIFC) += spi-meson-spifc.o
diff --git a/drivers/spi/spi-jcore.c b/drivers/spi/spi-jcore.c
new file mode 100644
index 0000000..7d2044a
--- /dev/null
+++ b/drivers/spi/spi-jcore.c
@@ -0,0 +1,232 @@
+/*
+ * J-Core SPI controller driver
+ *
+ * Copyright (C) 2012-2016 Smart Energy Instruments, Inc.
+ *
+ * Current version by Rich Felker
+ * Based loosely on initial version by Oleksandr G Zhadan
+ *
+ */
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/delay.h>
+
+#define DRV_NAME "jcore_spi"
+
+#define CTRL_REG 0x0
+#define DATA_REG 0x4
+
+#define JCORE_SPI_CTRL_XMIT 0x02
+#define JCORE_SPI_STAT_BUSY 0x02
+#define JCORE_SPI_CTRL_LOOP 0x08
+#define JCORE_SPI_CTRL_CS_BITS 0x15
+
+#define JCORE_SPI_WAIT_RDY_MAX_LOOP 2000000
+
+struct jcore_spi {
+ struct spi_master *master;
+ void __iomem *base;
+ unsigned int cs_reg;
+ unsigned int speed_reg;
+ unsigned int speed_hz;
+ unsigned int clock_freq;
+};
+
+static int jcore_spi_wait(void __iomem *ctrl_reg)
+{
+ unsigned timeout = JCORE_SPI_WAIT_RDY_MAX_LOOP;
+
+ do {
+ if (!(readl(ctrl_reg) & JCORE_SPI_STAT_BUSY))
+ return 0;
+ cpu_relax();
+ } while (--timeout);
+
+ return -EBUSY;
+}
+
+static void jcore_spi_program(struct jcore_spi *hw)
+{
+ void __iomem *ctrl_reg = hw->base + CTRL_REG;
+
+ if (jcore_spi_wait(ctrl_reg))
+ dev_err(hw->master->dev.parent,
+ "timeout waiting to program ctrl reg.\n");
+
+ writel(hw->cs_reg | hw->speed_reg, ctrl_reg);
+}
+
+static void jcore_spi_chipsel(struct spi_device *spi, bool value)
+{
+ struct jcore_spi *hw = spi_master_get_devdata(spi->master);
+ u32 csbit = 1U << (2 * spi->chip_select);
+
+ dev_dbg(hw->master->dev.parent, "chipselect %d\n", spi->chip_select);
+
+ if (value)
+ hw->cs_reg |= csbit;
+ else
+ hw->cs_reg &= ~csbit;
+
+ jcore_spi_program(hw);
+}
+
+static void jcore_spi_baudrate(struct jcore_spi *hw, int speed)
+{
+ if (speed == hw->speed_hz) return;
+ hw->speed_hz = speed;
+ if (speed >= hw->clock_freq / 2)
+ hw->speed_reg = 0;
+ else
+ hw->speed_reg = ((hw->clock_freq / 2 / speed) - 1) << 27;
+ jcore_spi_program(hw);
+ dev_dbg(hw->master->dev.parent, "speed=%d reg=0x%x\n",
+ speed, hw->speed_reg);
+}
+
+static int jcore_spi_txrx(struct spi_master *master, struct spi_device *spi,
+ struct spi_transfer *t)
+{
+ struct jcore_spi *hw = spi_master_get_devdata(master);
+
+ void __iomem *ctrl_reg = hw->base + CTRL_REG;
+ void __iomem *data_reg = hw->base + DATA_REG;
+ u32 xmit;
+
+ /* data buffers */
+ const unsigned char *tx;
+ unsigned char *rx;
+ unsigned int len;
+ unsigned int count;
+
+ jcore_spi_baudrate(hw, t->speed_hz);
+
+ xmit = hw->cs_reg | hw->speed_reg | JCORE_SPI_CTRL_XMIT;
+ tx = t->tx_buf;
+ rx = t->rx_buf;
+ len = t->len;
+
+ for (count = 0; count < len; count++) {
+ if (jcore_spi_wait(ctrl_reg))
+ break;
+
+ writel(tx ? *tx++ : 0, data_reg);
+ writel(xmit, ctrl_reg);
+
+ if (jcore_spi_wait(ctrl_reg))
+ break;
+
+ if (rx)
+ *rx++ = readl(data_reg);
+ }
+
+ spi_finalize_current_transfer(master);
+
+ if (count < len)
+ return -EREMOTEIO;
+
+ return 0;
+}
+
+static int jcore_spi_probe(struct platform_device *pdev)
+{
+ struct device_node *node = pdev->dev.of_node;
+ struct jcore_spi *hw;
+ struct spi_master *master;
+ struct resource *res;
+ u32 clock_freq;
+ struct clk *clk;
+ int err = -ENODEV;
+
+ master = spi_alloc_master(&pdev->dev, sizeof(struct jcore_spi));
+ if (!master)
+ return err;
+
+ /* Setup the master state. */
+ master->num_chipselect = 3;
+ master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
+ master->transfer_one = jcore_spi_txrx;
+ master->set_cs = jcore_spi_chipsel;
+ master->dev.of_node = node;
+ master->bus_num = pdev->id;
+
+ hw = spi_master_get_devdata(master);
+ hw->master = master;
+ platform_set_drvdata(pdev, hw);
+
+ /* Find and map our resources */
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res)
+ goto exit_busy;
+ if (!devm_request_mem_region(&pdev->dev, res->start,
+ resource_size(res), pdev->name))
+ goto exit_busy;
+ hw->base = devm_ioremap_nocache(&pdev->dev, res->start,
+ resource_size(res));
+ if (!hw->base)
+ goto exit_busy;
+
+ /*
+ * The SPI clock rate controlled via a configurable clock divider
+ * which is applied to the reference clock. A 50 MHz reference is
+ * most suitable for obtaining standard SPI clock rates, but some
+ * designs may have a different reference clock, and the DT must
+ * make the driver aware so that it can properly program the
+ * requested rate. If the clock is omitted, 50 MHz is assumed.
+ */
+ clock_freq = 50000000;
+ clk = devm_clk_get(&pdev->dev, "ref_clk");
+ if (!IS_ERR_OR_NULL(clk)) {
+ if (clk_enable(clk) == 0)
+ clock_freq = clk_get_rate(clk);
+ else
+ dev_warn(&pdev->dev, "could not enable ref_clk\n");
+ }
+ hw->clock_freq = clock_freq;
+
+ /* Initialize all CS bits to high. */
+ hw->cs_reg = JCORE_SPI_CTRL_CS_BITS;
+ jcore_spi_baudrate(hw, 400000);
+
+ /* Register our spi controller */
+ err = devm_spi_register_master(&pdev->dev, master);
+ if (err)
+ goto exit;
+
+ return 0;
+
+exit_busy:
+ err = -EBUSY;
+exit:
+ platform_set_drvdata(pdev, NULL);
+ spi_master_put(master);
+ return err;
+}
+
+static const struct of_device_id jcore_spi_of_match[] = {
+ { .compatible = "jcore,spi2" },
+ {},
+};
+
+static struct platform_driver jcore_spi_driver = {
+ .probe = jcore_spi_probe,
+ .driver = {
+ .name = DRV_NAME,
+ .of_match_table = jcore_spi_of_match,
+ },
+};
+
+module_platform_driver(jcore_spi_driver);
+
+MODULE_DESCRIPTION("J-Core SPI driver");
+MODULE_AUTHOR("Rich Felker <dalias-8zAoT0mYgF4@public.gmane.org>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" DRV_NAME);
--
2.8.1

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