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Subject[PATCH v7] spi: Add SPI driver for Mikrotik RB4xx series boards
Date
This driver mediates access between the connected CPLD and other devices
on the bus.

The m25p80-compatible boot flash and (some models) MMC use regular SPI,
bitbanged as required by the SoC. However the SPI-connected CPLD has
a two-wire mode, in which two bits are transferred per SPI clock
cycle. The second bit is transmitted with the SoC's CS2 pin.

Signed-off-by: Bert Vermeulen <bert@biot.com>
---
Changes in v7:
- use SPI_TX_DUAL/tx_nbits to signal two-wire mode
- use SPI_MASTER_MUST_TX for dummy writes
- use bits_per_word_mask to restrict word size
- properly disable/unprepare clock on module removal
- code cleanup
Changes in v6:
- removed unnecessary SPI mode check
- whitespace fixes


drivers/spi/Kconfig | 6 ++
drivers/spi/Makefile | 1 +
drivers/spi/spi-rb4xx.c | 210 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 217 insertions(+)
create mode 100644 drivers/spi/spi-rb4xx.c

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index ab8dfbe..8b1beaf6 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -429,6 +429,12 @@ config SPI_ROCKCHIP
The main usecase of this controller is to use spi flash as boot
device.

+config SPI_RB4XX
+ tristate "Mikrotik RB4XX SPI master"
+ depends on SPI_MASTER && ATH79
+ help
+ SPI controller driver for the Mikrotik RB4xx series boards.
+
config SPI_RSPI
tristate "Renesas RSPI/QSPI controller"
depends on SUPERH || ARCH_SHMOBILE || COMPILE_TEST
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index d8cbf65..0218f39 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -66,6 +66,7 @@ obj-$(CONFIG_SPI_PXA2XX) += spi-pxa2xx-platform.o
obj-$(CONFIG_SPI_PXA2XX_PCI) += spi-pxa2xx-pci.o
obj-$(CONFIG_SPI_QUP) += spi-qup.o
obj-$(CONFIG_SPI_ROCKCHIP) += spi-rockchip.o
+obj-$(CONFIG_SPI_RB4XX) += spi-rb4xx.o
obj-$(CONFIG_SPI_RSPI) += spi-rspi.o
obj-$(CONFIG_SPI_S3C24XX) += spi-s3c24xx-hw.o
spi-s3c24xx-hw-y := spi-s3c24xx.o
diff --git a/drivers/spi/spi-rb4xx.c b/drivers/spi/spi-rb4xx.c
new file mode 100644
index 0000000..9b449d4
--- /dev/null
+++ b/drivers/spi/spi-rb4xx.c
@@ -0,0 +1,210 @@
+/*
+ * SPI controller driver for the Mikrotik RB4xx boards
+ *
+ * Copyright (C) 2010 Gabor Juhos <juhosg@openwrt.org>
+ * Copyright (C) 2015 Bert Vermeulen <bert@biot.com>
+ *
+ * This file was based on the patches for Linux 2.6.27.39 published by
+ * MikroTik for their RouterBoard 4xx series devices.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/spi/spi.h>
+
+#include <asm/mach-ath79/ar71xx_regs.h>
+
+struct rb4xx_spi {
+ void __iomem *base;
+ struct clk *clk;
+};
+
+static inline u32 rb4xx_read(struct rb4xx_spi *rbspi, u32 reg)
+{
+ return __raw_readl(rbspi->base + reg);
+}
+
+static inline void rb4xx_write(struct rb4xx_spi *rbspi, u32 reg, u32 value)
+{
+ __raw_writel(value, rbspi->base + reg);
+}
+
+static inline void do_spi_clk(struct rb4xx_spi *rbspi, u32 spi_ioc, int value)
+{
+ u32 regval;
+
+ regval = spi_ioc;
+ if (value & BIT(0))
+ regval |= AR71XX_SPI_IOC_DO;
+
+ rb4xx_write(rbspi, AR71XX_SPI_REG_IOC, regval);
+ rb4xx_write(rbspi, AR71XX_SPI_REG_IOC, regval | AR71XX_SPI_IOC_CLK);
+}
+
+static void do_spi_byte(struct rb4xx_spi *rbspi, u32 spi_ioc, u8 byte)
+{
+ int i;
+
+ for (i = 7; i >= 0; i--)
+ do_spi_clk(rbspi, spi_ioc, byte >> i);
+}
+
+/* The CS2 pin is used to clock in a second bit per clock cycle. */
+static inline void do_spi_clk_two(struct rb4xx_spi *rbspi, u32 spi_ioc,
+ u8 value)
+{
+ u32 regval;
+
+ regval = spi_ioc;
+ if (value & BIT(1))
+ regval |= AR71XX_SPI_IOC_DO;
+ if (value & BIT(0))
+ regval |= AR71XX_SPI_IOC_CS2;
+
+ rb4xx_write(rbspi, AR71XX_SPI_REG_IOC, regval);
+ rb4xx_write(rbspi, AR71XX_SPI_REG_IOC, regval | AR71XX_SPI_IOC_CLK);
+}
+
+/* Two bits at a time, msb first */
+static void do_spi_byte_two(struct rb4xx_spi *rbspi, u32 spi_ioc, u8 byte)
+{
+ do_spi_clk_two(rbspi, spi_ioc, byte >> 6);
+ do_spi_clk_two(rbspi, spi_ioc, byte >> 4);
+ do_spi_clk_two(rbspi, spi_ioc, byte >> 2);
+ do_spi_clk_two(rbspi, spi_ioc, byte >> 0);
+}
+
+static void rb4xx_set_cs(struct spi_device *spi, bool enable)
+{
+ struct rb4xx_spi *rbspi = spi_master_get_devdata(spi->master);
+
+ /*
+ * Setting CS is done along with bitbanging the actual values,
+ * since it's all on the same hardware register. However the
+ * CPLD needs CS deselected after every command.
+ */
+ if (!enable)
+ rb4xx_write(rbspi, AR71XX_SPI_REG_IOC,
+ AR71XX_SPI_IOC_CS0 | AR71XX_SPI_IOC_CS1);
+}
+
+static int rb4xx_transfer_one(struct spi_master *master,
+ struct spi_device *spi, struct spi_transfer *t)
+{
+ struct rb4xx_spi *rbspi = spi_master_get_devdata(master);
+ int i;
+ u32 spi_ioc;
+ u8 *rx_buf;
+ const u8 *tx_buf;
+
+ /*
+ * Prime the SPI register with the SPI device selected. The m25p80 boot
+ * flash and CPLD share the CS0 pin. This works because the CPLD's
+ * command set was designed to almost not clash with that of the
+ * boot flash.
+ */
+ if (spi->chip_select == 2)
+ /* MMC */
+ spi_ioc = AR71XX_SPI_IOC_CS0;
+ else
+ /* Boot flash and CPLD */
+ spi_ioc = AR71XX_SPI_IOC_CS1;
+
+ tx_buf = t->tx_buf;
+ rx_buf = t->rx_buf;
+ for (i = 0; i < t->len; ++i) {
+ if (t->tx_nbits == SPI_NBITS_DUAL)
+ /* CPLD can use two-wire transfers */
+ do_spi_byte_two(rbspi, spi_ioc, tx_buf[i]);
+ else
+ do_spi_byte(rbspi, spi_ioc, tx_buf[i]);
+ if (!rx_buf)
+ continue;
+ rx_buf[i] = rb4xx_read(rbspi, AR71XX_SPI_REG_RDS);
+ }
+ spi_finalize_current_transfer(master);
+
+ return 0;
+}
+
+static int rb4xx_spi_probe(struct platform_device *pdev)
+{
+ struct spi_master *master;
+ struct clk *ahb_clk;
+ struct rb4xx_spi *rbspi;
+ struct resource *r;
+ int err;
+ void __iomem *spi_base;
+
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ spi_base = devm_ioremap_resource(&pdev->dev, r);
+ if (!spi_base)
+ return PTR_ERR(spi_base);
+
+ master = spi_alloc_master(&pdev->dev, sizeof(*rbspi));
+ if (!master)
+ return -ENOMEM;
+
+ ahb_clk = devm_clk_get(&pdev->dev, "ahb");
+ if (IS_ERR(ahb_clk))
+ return PTR_ERR(ahb_clk);
+
+ master->bus_num = 0;
+ master->num_chipselect = 3;
+ master->mode_bits = SPI_TX_DUAL;
+ master->bits_per_word_mask = BIT(7);
+ master->flags = SPI_MASTER_MUST_TX;
+ master->transfer_one = rb4xx_transfer_one;
+ master->set_cs = rb4xx_set_cs;
+
+ err = devm_spi_register_master(&pdev->dev, master);
+ if (err) {
+ dev_err(&pdev->dev, "failed to register SPI master\n");
+ return err;
+ }
+
+ err = clk_prepare_enable(ahb_clk);
+ if (err)
+ return err;
+
+ rbspi = spi_master_get_devdata(master);
+ rbspi->base = spi_base;
+ rbspi->clk = ahb_clk;
+ platform_set_drvdata(pdev, rbspi);
+
+ /* Enable SPI */
+ rb4xx_write(rbspi, AR71XX_SPI_REG_FS, AR71XX_SPI_FS_GPIO);
+
+ return 0;
+}
+
+static int rb4xx_spi_remove(struct platform_device *pdev)
+{
+ struct rb4xx_spi *rbspi = platform_get_drvdata(pdev);
+
+ clk_disable_unprepare(rbspi->clk);
+
+ return 0;
+}
+
+static struct platform_driver rb4xx_spi_drv = {
+ .probe = rb4xx_spi_probe,
+ .remove = rb4xx_spi_remove,
+ .driver = {
+ .name = "rb4xx-spi",
+ },
+};
+
+module_platform_driver(rb4xx_spi_drv);
+
+MODULE_DESCRIPTION("Mikrotik RB4xx SPI controller driver");
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_AUTHOR("Bert Vermeulen <bert@biot.com>");
+MODULE_LICENSE("GPL v2");
--
1.9.1


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