diff options
Diffstat (limited to 'drivers/spi/spi-bcm2835.c')
| -rw-r--r-- | drivers/spi/spi-bcm2835.c | 422 |
1 files changed, 422 insertions, 0 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c new file mode 100644 index 000000000000..89c0b5033114 --- /dev/null +++ b/drivers/spi/spi-bcm2835.c @@ -0,0 +1,422 @@ +/* + * Driver for Broadcom BCM2835 SPI Controllers + * + * Copyright (C) 2012 Chris Boot + * Copyright (C) 2013 Stephen Warren + * + * This driver is inspired by: + * spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org> + * spi-atmel.c, Copyright (C) 2006 Atmel Corporation + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + */ + +#include <linux/clk.h> +#include <linux/completion.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/interrupt.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_irq.h> +#include <linux/of_device.h> +#include <linux/spi/spi.h> + +/* SPI register offsets */ +#define BCM2835_SPI_CS 0x00 +#define BCM2835_SPI_FIFO 0x04 +#define BCM2835_SPI_CLK 0x08 +#define BCM2835_SPI_DLEN 0x0c +#define BCM2835_SPI_LTOH 0x10 +#define BCM2835_SPI_DC 0x14 + +/* Bitfields in CS */ +#define BCM2835_SPI_CS_LEN_LONG 0x02000000 +#define BCM2835_SPI_CS_DMA_LEN 0x01000000 +#define BCM2835_SPI_CS_CSPOL2 0x00800000 +#define BCM2835_SPI_CS_CSPOL1 0x00400000 +#define BCM2835_SPI_CS_CSPOL0 0x00200000 +#define BCM2835_SPI_CS_RXF 0x00100000 +#define BCM2835_SPI_CS_RXR 0x00080000 +#define BCM2835_SPI_CS_TXD 0x00040000 +#define BCM2835_SPI_CS_RXD 0x00020000 +#define BCM2835_SPI_CS_DONE 0x00010000 +#define BCM2835_SPI_CS_LEN 0x00002000 +#define BCM2835_SPI_CS_REN 0x00001000 +#define BCM2835_SPI_CS_ADCS 0x00000800 +#define BCM2835_SPI_CS_INTR 0x00000400 +#define BCM2835_SPI_CS_INTD 0x00000200 +#define BCM2835_SPI_CS_DMAEN 0x00000100 +#define BCM2835_SPI_CS_TA 0x00000080 +#define BCM2835_SPI_CS_CSPOL 0x00000040 +#define BCM2835_SPI_CS_CLEAR_RX 0x00000020 +#define BCM2835_SPI_CS_CLEAR_TX 0x00000010 +#define BCM2835_SPI_CS_CPOL 0x00000008 +#define BCM2835_SPI_CS_CPHA 0x00000004 +#define BCM2835_SPI_CS_CS_10 0x00000002 +#define BCM2835_SPI_CS_CS_01 0x00000001 + +#define BCM2835_SPI_TIMEOUT_MS 30000 +#define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_NO_CS) + +#define DRV_NAME "spi-bcm2835" + +struct bcm2835_spi { + void __iomem *regs; + struct clk *clk; + int irq; + struct completion done; + const u8 *tx_buf; + u8 *rx_buf; + int len; +}; + +static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg) +{ + return readl(bs->regs + reg); +} + +static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val) +{ + writel(val, bs->regs + reg); +} + +static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs, int len) +{ + u8 byte; + + while (len--) { + byte = bcm2835_rd(bs, BCM2835_SPI_FIFO); + if (bs->rx_buf) + *bs->rx_buf++ = byte; + } +} + +static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs, int len) +{ + u8 byte; + + if (len > bs->len) + len = bs->len; + + while (len--) { + byte = bs->tx_buf ? *bs->tx_buf++ : 0; + bcm2835_wr(bs, BCM2835_SPI_FIFO, byte); + bs->len--; + } +} + +static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id) +{ + struct spi_master *master = dev_id; + struct bcm2835_spi *bs = spi_master_get_devdata(master); + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + + /* + * RXR - RX needs Reading. This means 12 (or more) bytes have been + * transmitted and hence 12 (or more) bytes have been received. + * + * The FIFO is 16-bytes deep. We check for this interrupt to keep the + * FIFO full; we have a 4-byte-time buffer for IRQ latency. We check + * this before DONE (TX empty) just in case we delayed processing this + * interrupt for some reason. + * + * We only check for this case if we have more bytes to TX; at the end + * of the transfer, we ignore this pipelining optimization, and let + * bcm2835_spi_finish_transfer() drain the RX FIFO. + */ + if (bs->len && (cs & BCM2835_SPI_CS_RXR)) { + /* Read 12 bytes of data */ + bcm2835_rd_fifo(bs, 12); + + /* Write up to 12 bytes */ + bcm2835_wr_fifo(bs, 12); + + /* + * We must have written something to the TX FIFO due to the + * bs->len check above, so cannot be DONE. Hence, return + * early. Note that DONE could also be set if we serviced an + * RXR interrupt really late. + */ + return IRQ_HANDLED; + } + + /* + * DONE - TX empty. This occurs when we first enable the transfer + * since we do not pre-fill the TX FIFO. At any other time, given that + * we refill the TX FIFO above based on RXR, and hence ignore DONE if + * RXR is set, DONE really does mean end-of-transfer. + */ + if (cs & BCM2835_SPI_CS_DONE) { + if (bs->len) { /* First interrupt in a transfer */ + bcm2835_wr_fifo(bs, 16); + } else { /* Transfer complete */ + /* Disable SPI interrupts */ + cs &= ~(BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD); + bcm2835_wr(bs, BCM2835_SPI_CS, cs); + + /* + * Wake up bcm2835_spi_transfer_one(), which will call + * bcm2835_spi_finish_transfer(), to drain the RX FIFO. + */ + complete(&bs->done); + } + + return IRQ_HANDLED; + } + + return IRQ_NONE; +} + +static int bcm2835_spi_start_transfer(struct spi_device *spi, + struct spi_transfer *tfr) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(spi->master); + unsigned long spi_hz, clk_hz, cdiv; + u32 cs = BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA; + + spi_hz = tfr->speed_hz; + clk_hz = clk_get_rate(bs->clk); + + if (spi_hz >= clk_hz / 2) { + cdiv = 2; /* clk_hz/2 is the fastest we can go */ + } else if (spi_hz) { + /* CDIV must be a power of two */ + cdiv = roundup_pow_of_two(DIV_ROUND_UP(clk_hz, spi_hz)); + + if (cdiv >= 65536) + cdiv = 0; /* 0 is the slowest we can go */ + } else + cdiv = 0; /* 0 is the slowest we can go */ + + if (spi->mode & SPI_CPOL) + cs |= BCM2835_SPI_CS_CPOL; + if (spi->mode & SPI_CPHA) + cs |= BCM2835_SPI_CS_CPHA; + + if (!(spi->mode & SPI_NO_CS)) { + if (spi->mode & SPI_CS_HIGH) { + cs |= BCM2835_SPI_CS_CSPOL; + cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select; + } + + cs |= spi->chip_select; + } + + INIT_COMPLETION(bs->done); + bs->tx_buf = tfr->tx_buf; + bs->rx_buf = tfr->rx_buf; + bs->len = tfr->len; + + bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); + /* + * Enable the HW block. This will immediately trigger a DONE (TX + * empty) interrupt, upon which we will fill the TX FIFO with the + * first TX bytes. Pre-filling the TX FIFO here to avoid the + * interrupt doesn't work:-( + */ + bcm2835_wr(bs, BCM2835_SPI_CS, cs); + + return 0; +} + +static int bcm2835_spi_finish_transfer(struct spi_device *spi, + struct spi_transfer *tfr, bool cs_change) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(spi->master); + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + + /* Drain RX FIFO */ + while (cs & BCM2835_SPI_CS_RXD) { + bcm2835_rd_fifo(bs, 1); + cs = bcm2835_rd(bs, BCM2835_SPI_CS); + } + + if (tfr->delay_usecs) + udelay(tfr->delay_usecs); + + if (cs_change) + /* Clear TA flag */ + bcm2835_wr(bs, BCM2835_SPI_CS, cs & ~BCM2835_SPI_CS_TA); + + return 0; +} + +static int bcm2835_spi_transfer_one(struct spi_master *master, + struct spi_message *mesg) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(master); + struct spi_transfer *tfr; + struct spi_device *spi = mesg->spi; + int err = 0; + unsigned int timeout; + bool cs_change; + + list_for_each_entry(tfr, &mesg->transfers, transfer_list) { + err = bcm2835_spi_start_transfer(spi, tfr); + if (err) + goto out; + + timeout = wait_for_completion_timeout(&bs->done, + msecs_to_jiffies(BCM2835_SPI_TIMEOUT_MS)); + if (!timeout) { + err = -ETIMEDOUT; + goto out; + } + + cs_change = tfr->cs_change || + list_is_last(&tfr->transfer_list, &mesg->transfers); + + err = bcm2835_spi_finish_transfer(spi, tfr, cs_change); + if (err) + goto out; + + mesg->actual_length += (tfr->len - bs->len); + } + +out: + /* Clear FIFOs, and disable the HW block */ + bcm2835_wr(bs, BCM2835_SPI_CS, + BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); + mesg->status = err; + spi_finalize_current_message(master); + + return 0; +} + +static int bcm2835_spi_probe(struct platform_device *pdev) +{ + struct spi_master *master; + struct bcm2835_spi *bs; + struct resource *res; + int err; + + master = spi_alloc_master(&pdev->dev, sizeof(*bs)); + if (!master) { + dev_err(&pdev->dev, "spi_alloc_master() failed\n"); + return -ENOMEM; + } + + platform_set_drvdata(pdev, master); + + master->mode_bits = BCM2835_SPI_MODE_BITS; + master->bits_per_word_mask = BIT(8 - 1); + master->bus_num = -1; + master->num_chipselect = 3; + master->transfer_one_message = bcm2835_spi_transfer_one; + master->dev.of_node = pdev->dev.of_node; + + bs = spi_master_get_devdata(master); + + init_completion(&bs->done); + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) { + dev_err(&pdev->dev, "could not get memory resource\n"); + err = -ENODEV; + goto out_master_put; + } + + bs->regs = devm_request_and_ioremap(&pdev->dev, res); + if (!bs->regs) { + dev_err(&pdev->dev, "could not request/map memory region\n"); + err = -ENODEV; + goto out_master_put; + } + + bs->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(bs->clk)) { + err = PTR_ERR(bs->clk); + dev_err(&pdev->dev, "could not get clk: %d\n", err); + goto out_master_put; + } + + bs->irq = irq_of_parse_and_map(pdev->dev.of_node, 0); + if (bs->irq <= 0) { + dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq); + err = bs->irq ? bs->irq : -ENODEV; + goto out_master_put; + } + + clk_prepare_enable(bs->clk); + + err = request_irq(bs->irq, bcm2835_spi_interrupt, 0, + dev_name(&pdev->dev), master); + if (err) { + dev_err(&pdev->dev, "could not request IRQ: %d\n", err); + goto out_clk_disable; + } + + /* initialise the hardware */ + bcm2835_wr(bs, BCM2835_SPI_CS, + BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); + + err = spi_register_master(master); + if (err) { + dev_err(&pdev->dev, "could not register SPI master: %d\n", err); + goto out_free_irq; + } + + return 0; + +out_free_irq: + free_irq(bs->irq, master); +out_clk_disable: + clk_disable_unprepare(bs->clk); +out_master_put: + spi_master_put(master); + return err; +} + +static int bcm2835_spi_remove(struct platform_device *pdev) +{ + struct spi_master *master = platform_get_drvdata(pdev); + struct bcm2835_spi *bs = spi_master_get_devdata(master); + + free_irq(bs->irq, master); + spi_unregister_master(master); + + /* Clear FIFOs, and disable the HW block */ + bcm2835_wr(bs, BCM2835_SPI_CS, + BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); + + clk_disable_unprepare(bs->clk); + spi_master_put(master); + + return 0; +} + +static const struct of_device_id bcm2835_spi_match[] = { + { .compatible = "brcm,bcm2835-spi", }, + {} +}; +MODULE_DEVICE_TABLE(of, bcm2835_spi_match); + +static struct platform_driver bcm2835_spi_driver = { + .driver = { + .name = DRV_NAME, + .owner = THIS_MODULE, + .of_match_table = bcm2835_spi_match, + }, + .probe = bcm2835_spi_probe, + .remove = bcm2835_spi_remove, +}; +module_platform_driver(bcm2835_spi_driver); + +MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835"); +MODULE_AUTHOR("Chris Boot <bootc@bootc.net>"); +MODULE_LICENSE("GPL v2"); |