diff options
Diffstat (limited to 'drivers/spi/spi-bcm2835.c')
| -rw-r--r-- | drivers/spi/spi-bcm2835.c | 517 |
1 files changed, 517 insertions, 0 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c new file mode 100644 index 000000000..37875cf94 --- /dev/null +++ b/drivers/spi/spi-bcm2835.c @@ -0,0 +1,517 @@ +/* + * Driver for Broadcom BCM2835 SPI Controllers + * + * Copyright (C) 2012 Chris Boot + * Copyright (C) 2013 Stephen Warren + * Copyright (C) 2015 Martin Sperl + * + * 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. + */ + +#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_gpio.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_POLLING_LIMIT_US 30 +#define BCM2835_SPI_TIMEOUT_MS 30000 +#define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \ + | SPI_NO_CS | SPI_3WIRE) + +#define DRV_NAME "spi-bcm2835" + +struct bcm2835_spi { + void __iomem *regs; + struct clk *clk; + int irq; + const u8 *tx_buf; + u8 *rx_buf; + int tx_len; + int rx_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) +{ + u8 byte; + + while ((bs->rx_len) && + (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_RXD)) { + byte = bcm2835_rd(bs, BCM2835_SPI_FIFO); + if (bs->rx_buf) + *bs->rx_buf++ = byte; + bs->rx_len--; + } +} + +static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs) +{ + u8 byte; + + while ((bs->tx_len) && + (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_TXD)) { + byte = bs->tx_buf ? *bs->tx_buf++ : 0; + bcm2835_wr(bs, BCM2835_SPI_FIFO, byte); + bs->tx_len--; + } +} + +static void bcm2835_spi_reset_hw(struct spi_master *master) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(master); + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + + /* Disable SPI interrupts and transfer */ + cs &= ~(BCM2835_SPI_CS_INTR | + BCM2835_SPI_CS_INTD | + BCM2835_SPI_CS_TA); + /* and reset RX/TX FIFOS */ + cs |= BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX; + + /* and reset the SPI_HW */ + bcm2835_wr(bs, BCM2835_SPI_CS, cs); +} + +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); + + /* Read as many bytes as possible from FIFO */ + bcm2835_rd_fifo(bs); + /* Write as many bytes as possible to FIFO */ + bcm2835_wr_fifo(bs); + + /* based on flags decide if we can finish the transfer */ + if (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_DONE) { + /* Transfer complete - reset SPI HW */ + bcm2835_spi_reset_hw(master); + /* wake up the framework */ + complete(&master->xfer_completion); + } + + return IRQ_HANDLED; +} + +static int bcm2835_spi_transfer_one_poll(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr, + u32 cs, + unsigned long xfer_time_us) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(master); + /* set timeout to 1 second of maximum polling */ + unsigned long timeout = jiffies + HZ; + + /* enable HW block without interrupts */ + bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA); + + /* loop until finished the transfer */ + while (bs->rx_len) { + /* read from fifo as much as possible */ + bcm2835_rd_fifo(bs); + /* fill in tx fifo as much as possible */ + bcm2835_wr_fifo(bs); + /* if we still expect some data after the read, + * check for a possible timeout + */ + if (bs->rx_len && time_after(jiffies, timeout)) { + /* Transfer complete - reset SPI HW */ + bcm2835_spi_reset_hw(master); + /* and return timeout */ + return -ETIMEDOUT; + } + } + + /* Transfer complete - reset SPI HW */ + bcm2835_spi_reset_hw(master); + /* and return without waiting for completion */ + return 0; +} + +static int bcm2835_spi_transfer_one_irq(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr, + u32 cs) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(master); + + /* fill in fifo if we have gpio-cs + * note that there have been rare events where the native-CS + * flapped for <1us which may change the behaviour + * with gpio-cs this does not happen, so it is implemented + * only for this case + */ + if (gpio_is_valid(spi->cs_gpio)) { + /* enable HW block, but without interrupts enabled + * this would triggern an immediate interrupt + */ + bcm2835_wr(bs, BCM2835_SPI_CS, + cs | BCM2835_SPI_CS_TA); + /* fill in tx fifo as much as possible */ + bcm2835_wr_fifo(bs); + } + + /* + * 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:-( + */ + cs |= BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA; + bcm2835_wr(bs, BCM2835_SPI_CS, cs); + + /* signal that we need to wait for completion */ + return 1; +} + +static int bcm2835_spi_transfer_one(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr) +{ + struct bcm2835_spi *bs = spi_master_get_devdata(master); + unsigned long spi_hz, clk_hz, cdiv; + unsigned long spi_used_hz, xfer_time_us; + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + + /* set clock */ + 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 multiple of two */ + cdiv = DIV_ROUND_UP(clk_hz, spi_hz); + cdiv += (cdiv % 2); + + if (cdiv >= 65536) + cdiv = 0; /* 0 is the slowest we can go */ + } else { + cdiv = 0; /* 0 is the slowest we can go */ + } + spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536); + bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv); + + /* handle all the modes */ + if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf)) + cs |= BCM2835_SPI_CS_REN; + if (spi->mode & SPI_CPOL) + cs |= BCM2835_SPI_CS_CPOL; + if (spi->mode & SPI_CPHA) + cs |= BCM2835_SPI_CS_CPHA; + + /* for gpio_cs set dummy CS so that no HW-CS get changed + * we can not run this in bcm2835_spi_set_cs, as it does + * not get called for cs_gpio cases, so we need to do it here + */ + if (gpio_is_valid(spi->cs_gpio) || (spi->mode & SPI_NO_CS)) + cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01; + + /* set transmit buffers and length */ + bs->tx_buf = tfr->tx_buf; + bs->rx_buf = tfr->rx_buf; + bs->tx_len = tfr->len; + bs->rx_len = tfr->len; + + /* calculate the estimated time in us the transfer runs */ + xfer_time_us = tfr->len + * 9 /* clocks/byte - SPI-HW waits 1 clock after each byte */ + * 1000000 / spi_used_hz; + + /* for short requests run polling*/ + if (xfer_time_us <= BCM2835_SPI_POLLING_LIMIT_US) + return bcm2835_spi_transfer_one_poll(master, spi, tfr, + cs, xfer_time_us); + + return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs); +} + +static void bcm2835_spi_handle_err(struct spi_master *master, + struct spi_message *msg) +{ + bcm2835_spi_reset_hw(master); +} + +static void bcm2835_spi_set_cs(struct spi_device *spi, bool gpio_level) +{ + /* + * we can assume that we are "native" as per spi_set_cs + * calling us ONLY when cs_gpio is not set + * we can also assume that we are CS < 3 as per bcm2835_spi_setup + * we would not get called because of error handling there. + * the level passed is the electrical level not enabled/disabled + * so it has to get translated back to enable/disable + * see spi_set_cs in spi.c for the implementation + */ + + struct spi_master *master = spi->master; + struct bcm2835_spi *bs = spi_master_get_devdata(master); + u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS); + bool enable; + + /* calculate the enable flag from the passed gpio_level */ + enable = (spi->mode & SPI_CS_HIGH) ? gpio_level : !gpio_level; + + /* set flags for "reverse" polarity in the registers */ + if (spi->mode & SPI_CS_HIGH) { + /* set the correct CS-bits */ + cs |= BCM2835_SPI_CS_CSPOL; + cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select; + } else { + /* clean the CS-bits */ + cs &= ~BCM2835_SPI_CS_CSPOL; + cs &= ~(BCM2835_SPI_CS_CSPOL0 << spi->chip_select); + } + + /* select the correct chip_select depending on disabled/enabled */ + if (enable) { + /* set cs correctly */ + if (spi->mode & SPI_NO_CS) { + /* use the "undefined" chip-select */ + cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01; + } else { + /* set the chip select */ + cs &= ~(BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01); + cs |= spi->chip_select; + } + } else { + /* disable CSPOL which puts HW-CS into deselected state */ + cs &= ~BCM2835_SPI_CS_CSPOL; + /* use the "undefined" chip-select as precaution */ + cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01; + } + + /* finally set the calculated flags in SPI_CS */ + bcm2835_wr(bs, BCM2835_SPI_CS, cs); +} + +static int chip_match_name(struct gpio_chip *chip, void *data) +{ + return !strcmp(chip->label, data); +} + +static int bcm2835_spi_setup(struct spi_device *spi) +{ + int err; + struct gpio_chip *chip; + /* + * sanity checking the native-chipselects + */ + if (spi->mode & SPI_NO_CS) + return 0; + if (gpio_is_valid(spi->cs_gpio)) + return 0; + if (spi->chip_select > 1) { + /* error in the case of native CS requested with CS > 1 + * officially there is a CS2, but it is not documented + * which GPIO is connected with that... + */ + dev_err(&spi->dev, + "setup: only two native chip-selects are supported\n"); + return -EINVAL; + } + /* now translate native cs to GPIO */ + + /* get the gpio chip for the base */ + chip = gpiochip_find("pinctrl-bcm2835", chip_match_name); + if (!chip) + return 0; + + /* and calculate the real CS */ + spi->cs_gpio = chip->base + 8 - spi->chip_select; + + /* and set up the "mode" and level */ + dev_info(&spi->dev, "setting up native-CS%i as GPIO %i\n", + spi->chip_select, spi->cs_gpio); + + /* set up GPIO as output and pull to the correct level */ + err = gpio_direction_output(spi->cs_gpio, + (spi->mode & SPI_CS_HIGH) ? 0 : 1); + if (err) { + dev_err(&spi->dev, + "could not set CS%i gpio %i as output: %i", + spi->chip_select, spi->cs_gpio, err); + return err; + } + /* the implementation of pinctrl-bcm2835 currently does not + * set the GPIO value when using gpio_direction_output + * so we are setting it here explicitly + */ + gpio_set_value(spi->cs_gpio, (spi->mode & SPI_CS_HIGH) ? 0 : 1); + + 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 = SPI_BPW_MASK(8); + master->num_chipselect = 3; + master->setup = bcm2835_spi_setup; + master->set_cs = bcm2835_spi_set_cs; + master->transfer_one = bcm2835_spi_transfer_one; + master->handle_err = bcm2835_spi_handle_err; + master->dev.of_node = pdev->dev.of_node; + + bs = spi_master_get_devdata(master); + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + bs->regs = devm_ioremap_resource(&pdev->dev, res); + if (IS_ERR(bs->regs)) { + err = PTR_ERR(bs->regs); + 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 = devm_request_irq(&pdev->dev, 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 with the default polarities */ + bcm2835_wr(bs, BCM2835_SPI_CS, + BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX); + + err = devm_spi_register_master(&pdev->dev, master); + if (err) { + dev_err(&pdev->dev, "could not register SPI master: %d\n", err); + goto out_clk_disable; + } + + return 0; + +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); + + /* 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); + + 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, + .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"); |