/*
* 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;
}
reinit_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 = SPI_BPW_MASK(8);
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);
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 */
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,
.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");