[PATCH 5/9] spi: add litex spiflash driver

[Antony Pavlov <antonynpavlov@gmail.com>]

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
---
 drivers/spi/Kconfig          |   3 +
 drivers/spi/Makefile         |   1 +
 drivers/spi/litex_spiflash.c | 242 +++++++++++++++++++++++++++++++++++
 3 files changed, 246 insertions(+)

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 323d93efeb..714d30e909 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -74,6 +74,9 @@ config DRIVER_SPI_IMX_2_3
 	depends on ARCH_IMX50 || ARCH_IMX51 || ARCH_IMX53 || ARCH_IMX6 || ARCH_IMX7 || ARCH_IMX8MQ
 	default y
 
+config DRIVER_SPI_LITEX_SPIFLASH
+	bool "Litex SPIFLASH bitbang master driver"
+
 config DRIVER_SPI_MXS
 	bool "i.MX (23,28) SPI Master driver"
 	depends on ARCH_IMX28
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 908d514a01..ac95ffc1db 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_DRIVER_SPI_ATH79) += ath79_spi.o
 obj-$(CONFIG_DRIVER_SPI_GPIO) += gpio_spi.o
 obj-$(CONFIG_DRIVER_SPI_FSL_QUADSPI) += spi-fsl-qspi.o
 obj-$(CONFIG_DRIVER_SPI_IMX) += imx_spi.o
+obj-$(CONFIG_DRIVER_SPI_LITEX_SPIFLASH) += litex_spiflash.o
 obj-$(CONFIG_DRIVER_SPI_MVEBU) += mvebu_spi.o
 obj-$(CONFIG_DRIVER_SPI_MXS) += mxs_spi.o
 obj-$(CONFIG_DRIVER_SPI_ALTERA) += altera_spi.o
diff --git a/drivers/spi/litex_spiflash.c b/drivers/spi/litex_spiflash.c
new file mode 100644
index 0000000000..2d6858c580
--- /dev/null
+++ b/drivers/spi/litex_spiflash.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2020 Antony Pavlov <antonynpavlov@gmail.com>
+ *
+ */
+
+#include <common.h>
+#include <init.h>
+#include <driver.h>
+#include <spi/spi.h>
+#include <io.h>
+#include <clock.h>
+
+struct litex_spiflash_spi {
+	struct spi_master	master;
+	void __iomem		*regs;
+	u32			val;
+};
+
+#define SPIFLASH_BITBANG 0x0
+#define  SPIFLASH_BB_MOSI BIT(0)
+#define  SPIFLASH_BB_CLK BIT(1)
+#define  SPIFLASH_BB_CSN BIT(2)
+#define  SPIFLASH_BB_DIR BIT(3)
+
+#define SPIFLASH_MISO 0x4
+#define SPIFLASH_BITBANG_EN 0x8
+
+static inline u32 litex_spiflash_spi_rr(struct litex_spiflash_spi *sp, int reg)
+{
+	return readl(sp->regs + reg);
+}
+
+static inline void litex_spiflash_spi_wr(struct litex_spiflash_spi *sp, u32 val, int reg)
+{
+	writel(val, sp->regs + reg);
+}
+
+static inline void setbits(struct litex_spiflash_spi *sp, int bits, int on)
+{
+	/*
+	 * We are the only user of SCSPTR so no locking is required.
+	 * Reading bit 2 and 0 in SCSPTR gives pin state as input.
+	 * Writing the same bits sets the output value.
+	 * This makes regular read-modify-write difficult so we
+	 * use sp->val to keep track of the latest register value.
+	 */
+
+	if (on)
+		sp->val |= bits;
+	else
+		sp->val &= ~bits;
+
+	litex_spiflash_spi_wr(sp, sp->val, SPIFLASH_BITBANG);
+}
+
+static inline struct litex_spiflash_spi *litex_spiflash_spidev_to_sp(struct spi_device *spi)
+{
+	return container_of(spi->master, struct litex_spiflash_spi, master);
+}
+
+static inline void setsck(struct spi_device *spi, int on)
+{
+	struct litex_spiflash_spi *sc = litex_spiflash_spidev_to_sp(spi);
+
+	setbits(sc, SPIFLASH_BB_CLK, on);
+}
+
+static inline void setmosi(struct spi_device *spi, int on)
+{
+	struct litex_spiflash_spi *sc = litex_spiflash_spidev_to_sp(spi);
+
+	sc->val &= ~SPIFLASH_BB_DIR;
+	setbits(sc, SPIFLASH_BB_MOSI, on);
+}
+
+static inline u32 getmiso(struct spi_device *spi)
+{
+	struct litex_spiflash_spi *sc = litex_spiflash_spidev_to_sp(spi);
+
+	setbits(sc, SPIFLASH_BB_DIR, 1);
+	return !!((litex_spiflash_spi_rr(sc, SPIFLASH_MISO) & 1));
+}
+
+#define spidelay(nsecs) udelay(nsecs/1000)
+
+#include "spi-bitbang-txrx.h"
+
+static inline void litex_spiflash_spi_chipselect(struct litex_spiflash_spi *sc, int on)
+{
+	setbits(sc, SPIFLASH_BB_CSN, on);
+}
+
+static int litex_spiflash_spi_setup(struct spi_device *spi)
+{
+	struct spi_master *master = spi->master;
+	struct device_d spi_dev = spi->dev;
+
+	if (spi->bits_per_word != 8) {
+		dev_err(master->dev, "master doesn't support %d bits per word requested by %s\n",
+			spi->bits_per_word, spi_dev.name);
+		return -EINVAL;
+	}
+
+	if ((spi->mode & (SPI_CPHA | SPI_CPOL)) != SPI_MODE_0) {
+		dev_err(master->dev, "master doesn't support SPI_MODE%d requested by %s\n",
+			spi->mode & (SPI_CPHA | SPI_CPOL), spi_dev.name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int litex_spiflash_spi_read(struct spi_device *spi, void *buf, size_t nbyte)
+{
+	ssize_t cnt = 0;
+	u8 *rxf_buf = buf;
+
+	while (cnt < nbyte) {
+		*rxf_buf = bitbang_txrx_be_cpha1(spi, 1000, 1, 0, 8);
+		rxf_buf++;
+		cnt++;
+	}
+
+	return cnt;
+}
+
+static int litex_spiflash_spi_write(struct spi_device *spi,
+				const void *buf, size_t nbyte)
+{
+	ssize_t cnt = 0;
+	const u8 *txf_buf = buf;
+
+	while (cnt < nbyte) {
+		bitbang_txrx_be_cpha1(spi, 1000, 1, (u32)*txf_buf, 8);
+		txf_buf++;
+		cnt++;
+	}
+
+	return 0;
+}
+
+static int litex_spiflash_spi_transfer(struct spi_device *spi, struct spi_message *mesg)
+{
+	struct litex_spiflash_spi *sc = litex_spiflash_spidev_to_sp(spi);
+	struct spi_transfer *t;
+
+	mesg->actual_length = 0;
+
+	/* activate chip select signal */
+	litex_spiflash_spi_chipselect(sc, 0);
+
+	list_for_each_entry(t, &mesg->transfers, transfer_list) {
+
+		if (t->tx_buf)
+			litex_spiflash_spi_write(spi, t->tx_buf, t->len);
+
+		if (t->rx_buf)
+			litex_spiflash_spi_read(spi, t->rx_buf, t->len);
+
+		mesg->actual_length += t->len;
+	}
+
+	/* inactivate chip select signal */
+	litex_spiflash_spi_chipselect(sc, 1);
+
+	return 0;
+}
+
+static void litex_spiflash_spi_enable(struct litex_spiflash_spi *sp)
+{
+	u32 val;
+
+	/* set SPIFLASH_BB_DIR = 0 */
+	val = SPIFLASH_BB_CSN | SPIFLASH_BB_CLK | SPIFLASH_BB_MOSI;
+	litex_spiflash_spi_wr(sp, val, SPIFLASH_BITBANG);
+
+	/* enable GPIO mode */
+	litex_spiflash_spi_wr(sp, 1, SPIFLASH_BITBANG_EN);
+}
+
+static void litex_spiflash_spi_disable(struct litex_spiflash_spi *sp)
+{
+	/* disable GPIO mode */
+	litex_spiflash_spi_wr(sp, 0, SPIFLASH_BITBANG_EN);
+}
+
+static int litex_spiflash_spi_probe(struct device_d *dev)
+{
+	struct resource *iores;
+	struct spi_master *master;
+	struct litex_spiflash_spi *litex_spiflash_spi;
+
+	litex_spiflash_spi = xzalloc(sizeof(*litex_spiflash_spi));
+	dev->priv = litex_spiflash_spi;
+
+	master = &litex_spiflash_spi->master;
+	master->dev = dev;
+
+	master->bus_num = dev->id;
+	master->setup = litex_spiflash_spi_setup;
+	master->transfer = litex_spiflash_spi_transfer;
+	master->num_chipselect = 1;
+
+	iores = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(iores))
+		return PTR_ERR(iores);
+	litex_spiflash_spi->regs = IOMEM(iores->start);
+
+	litex_spiflash_spi_enable(litex_spiflash_spi);
+
+	/* inactivate chip select signal */
+	litex_spiflash_spi_chipselect(litex_spiflash_spi, 1);
+
+	spi_register_master(master);
+
+	return 0;
+}
+
+static void litex_spiflash_spi_remove(struct device_d *dev)
+{
+	struct litex_spiflash_spi *sp = dev->priv;
+
+	litex_spiflash_spi_disable(sp);
+}
+
+static __maybe_unused struct of_device_id litex_spiflash_spi_dt_ids[] = {
+	{
+		.compatible = "litex,spiflash",
+	},
+	{
+		/* sentinel */
+	}
+};
+
+static struct driver_d litex_spiflash_spi_driver = {
+	.name  = "litex-spiflash",
+	.probe = litex_spiflash_spi_probe,
+	.remove = litex_spiflash_spi_remove,
+	.of_compatible = DRV_OF_COMPAT(litex_spiflash_spi_dt_ids),
+};
+device_platform_driver(litex_spiflash_spi_driver);
-- 
2.31.1


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