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linux/drivers/spi/spi-bcm2835aux.c

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/*
* Driver for Broadcom BCM2835 auxiliary SPI Controllers
*
* the driver does not rely on the native chipselects at all
* but only uses the gpio type chipselects
*
* Based on: spi-bcm2835.c
*
* Copyright (C) 2015 Martin Sperl
*
* 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_address.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/regmap.h>
#include <linux/spi/spi.h>
#include <linux/spinlock.h>
/*
* spi register defines
*
* note there is garbage in the "official" documentation,
* so some data is taken from the file:
* brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h
* inside of:
* http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz
*/
/* SPI register offsets */
#define BCM2835_AUX_SPI_CNTL0 0x00
#define BCM2835_AUX_SPI_CNTL1 0x04
#define BCM2835_AUX_SPI_STAT 0x08
#define BCM2835_AUX_SPI_PEEK 0x0C
#define BCM2835_AUX_SPI_IO 0x20
#define BCM2835_AUX_SPI_TXHOLD 0x30
/* Bitfields in CNTL0 */
#define BCM2835_AUX_SPI_CNTL0_SPEED 0xFFF00000
#define BCM2835_AUX_SPI_CNTL0_SPEED_MAX 0xFFF
#define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT 20
#define BCM2835_AUX_SPI_CNTL0_CS 0x000E0000
#define BCM2835_AUX_SPI_CNTL0_POSTINPUT 0x00010000
#define BCM2835_AUX_SPI_CNTL0_VAR_CS 0x00008000
#define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH 0x00004000
#define BCM2835_AUX_SPI_CNTL0_DOUTHOLD 0x00003000
#define BCM2835_AUX_SPI_CNTL0_ENABLE 0x00000800
#define BCM2835_AUX_SPI_CNTL0_CPHA_IN 0x00000400
#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200
#define BCM2835_AUX_SPI_CNTL0_CPHA_OUT 0x00000100
#define BCM2835_AUX_SPI_CNTL0_CPOL 0x00000080
#define BCM2835_AUX_SPI_CNTL0_MSBF_OUT 0x00000040
#define BCM2835_AUX_SPI_CNTL0_SHIFTLEN 0x0000003F
/* Bitfields in CNTL1 */
#define BCM2835_AUX_SPI_CNTL1_CSHIGH 0x00000700
#define BCM2835_AUX_SPI_CNTL1_IDLE 0x00000080
#define BCM2835_AUX_SPI_CNTL1_TXEMPTY 0x00000040
#define BCM2835_AUX_SPI_CNTL1_MSBF_IN 0x00000002
#define BCM2835_AUX_SPI_CNTL1_KEEP_IN 0x00000001
/* Bitfields in STAT */
#define BCM2835_AUX_SPI_STAT_TX_LVL 0xFF000000
#define BCM2835_AUX_SPI_STAT_RX_LVL 0x00FF0000
#define BCM2835_AUX_SPI_STAT_TX_FULL 0x00000400
#define BCM2835_AUX_SPI_STAT_TX_EMPTY 0x00000200
#define BCM2835_AUX_SPI_STAT_RX_FULL 0x00000100
#define BCM2835_AUX_SPI_STAT_RX_EMPTY 0x00000080
#define BCM2835_AUX_SPI_STAT_BUSY 0x00000040
#define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F
/* timeout values */
#define BCM2835_AUX_SPI_POLLING_LIMIT_US 30
#define BCM2835_AUX_SPI_POLLING_JIFFIES 2
#define BCM2835_AUX_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
| SPI_NO_CS)
struct bcm2835aux_spi {
void __iomem *regs;
struct clk *clk;
int irq;
u32 cntl[2];
const u8 *tx_buf;
u8 *rx_buf;
int tx_len;
int rx_len;
int pending;
};
static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned reg)
{
return readl(bs->regs + reg);
}
static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned reg,
u32 val)
{
writel(val, bs->regs + reg);
}
static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs)
{
u32 data;
int count = min(bs->rx_len, 3);
data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO);
if (bs->rx_buf) {
switch (count) {
case 4:
*bs->rx_buf++ = (data >> 24) & 0xff;
/* fallthrough */
case 3:
*bs->rx_buf++ = (data >> 16) & 0xff;
/* fallthrough */
case 2:
*bs->rx_buf++ = (data >> 8) & 0xff;
/* fallthrough */
case 1:
*bs->rx_buf++ = (data >> 0) & 0xff;
/* fallthrough - no default */
}
}
bs->rx_len -= count;
bs->pending -= count;
}
static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
{
u32 data;
u8 byte;
int count;
int i;
/* gather up to 3 bytes to write to the FIFO */
count = min(bs->tx_len, 3);
data = 0;
for (i = 0; i < count; i++) {
byte = bs->tx_buf ? *bs->tx_buf++ : 0;
data |= byte << (8 * (2 - i));
}
/* and set the variable bit-length */
data |= (count * 8) << 24;
/* and decrement length */
bs->tx_len -= count;
bs->pending += count;
/* write to the correct TX-register */
if (bs->tx_len)
bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data);
else
bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data);
}
static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs)
{
/* disable spi clearing fifo and interrupts */
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0);
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0,
BCM2835_AUX_SPI_CNTL0_CLEARFIFO);
}
static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
{
struct spi_master *master = dev_id;
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
irqreturn_t ret = IRQ_NONE;
/* check if we have data to read */
while (bs->rx_len &&
(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
BCM2835_AUX_SPI_STAT_RX_EMPTY))) {
bcm2835aux_rd_fifo(bs);
ret = IRQ_HANDLED;
}
/* check if we have data to write */
while (bs->tx_len &&
(bs->pending < 12) &&
(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
BCM2835_AUX_SPI_STAT_TX_FULL))) {
bcm2835aux_wr_fifo(bs);
ret = IRQ_HANDLED;
}
/* and check if we have reached "done" */
while (bs->rx_len &&
(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
BCM2835_AUX_SPI_STAT_BUSY))) {
bcm2835aux_rd_fifo(bs);
ret = IRQ_HANDLED;
}
/* and if rx_len is 0 then wake up completion and disable spi */
if (!bs->rx_len) {
bcm2835aux_spi_reset_hw(bs);
complete(&master->xfer_completion);
}
/* and return */
return ret;
}
static int __bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
/* enable interrupts */
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
BCM2835_AUX_SPI_CNTL1_TXEMPTY |
BCM2835_AUX_SPI_CNTL1_IDLE);
/* and wait for finish... */
return 1;
}
static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
/* fill in registers and fifos before enabling interrupts */
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
/* fill in tx fifo with data before enabling interrupts */
while ((bs->tx_len) &&
(bs->pending < 12) &&
(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
BCM2835_AUX_SPI_STAT_TX_FULL))) {
bcm2835aux_wr_fifo(bs);
}
/* now run the interrupt mode */
return __bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
}
static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
unsigned long timeout;
u32 stat;
/* configure spi */
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
/* set the timeout */
timeout = jiffies + BCM2835_AUX_SPI_POLLING_JIFFIES;
/* loop until finished the transfer */
while (bs->rx_len) {
/* read status */
stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT);
/* fill in tx fifo with remaining data */
if ((bs->tx_len) && (!(stat & BCM2835_AUX_SPI_STAT_TX_FULL))) {
bcm2835aux_wr_fifo(bs);
continue;
}
/* read data from fifo for both cases */
if (!(stat & BCM2835_AUX_SPI_STAT_RX_EMPTY)) {
bcm2835aux_rd_fifo(bs);
continue;
}
if (!(stat & BCM2835_AUX_SPI_STAT_BUSY)) {
bcm2835aux_rd_fifo(bs);
continue;
}
/* there is still data pending to read check the timeout */
if (bs->rx_len && time_after(jiffies, timeout)) {
dev_dbg_ratelimited(&spi->dev,
"timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
jiffies - timeout,
bs->tx_len, bs->rx_len);
/* forward to interrupt handler */
return __bcm2835aux_spi_transfer_one_irq(master,
spi, tfr);
}
}
/* Transfer complete - reset SPI HW */
bcm2835aux_spi_reset_hw(bs);
/* and return without waiting for completion */
return 0;
}
static int bcm2835aux_spi_transfer_one(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
unsigned long spi_hz, clk_hz, speed;
unsigned long spi_used_hz;
unsigned long long xfer_time_us;
/* calculate the registers to handle
*
* note that we use the variable data mode, which
* is not optimal for longer transfers as we waste registers
* resulting (potentially) in more interrupts when transferring
* more than 12 bytes
*/
bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE |
BCM2835_AUX_SPI_CNTL0_VAR_WIDTH |
BCM2835_AUX_SPI_CNTL0_MSBF_OUT;
bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN;
/* set clock */
spi_hz = tfr->speed_hz;
clk_hz = clk_get_rate(bs->clk);
if (spi_hz >= clk_hz / 2) {
speed = 0;
} else if (spi_hz) {
speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1;
if (speed > BCM2835_AUX_SPI_CNTL0_SPEED_MAX)
speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
} else { /* the slowest we can go */
speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
}
bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;
spi_used_hz = clk_hz / (2 * (speed + 1));
/* handle all the modes */
if (spi->mode & SPI_CPOL)
bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL;
if (spi->mode & SPI_CPHA)
bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPHA_OUT |
BCM2835_AUX_SPI_CNTL0_CPHA_IN;
/* 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;
bs->pending = 0;
/* calculate the estimated time in us the transfer runs
* note that there are are 2 idle clocks after each
* chunk getting transferred - in our case the chunk size
* is 3 bytes, so we approximate this by 9 bits/byte
*/
xfer_time_us = tfr->len * 9 * 1000000;
do_div(xfer_time_us, spi_used_hz);
/* run in polling mode for short transfers */
if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
/* run in interrupt mode for all others */
return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
}
static void bcm2835aux_spi_handle_err(struct spi_master *master,
struct spi_message *msg)
{
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
bcm2835aux_spi_reset_hw(bs);
}
static int bcm2835aux_spi_probe(struct platform_device *pdev)
{
struct spi_master *master;
struct bcm2835aux_spi *bs;
struct resource *res;
unsigned long clk_hz;
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_AUX_SPI_MODE_BITS;
master->bits_per_word_mask = SPI_BPW_MASK(8);
master->num_chipselect = -1;
master->transfer_one = bcm2835aux_spi_transfer_one;
master->handle_err = bcm2835aux_spi_handle_err;
master->dev.of_node = pdev->dev.of_node;
bs = spi_master_get_devdata(master);
/* the main area */
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 ((!bs->clk) || (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 = platform_get_irq(pdev, 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;
}
/* this also enables the HW block */
err = clk_prepare_enable(bs->clk);
if (err) {
dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
goto out_master_put;
}
/* just checking if the clock returns a sane value */
clk_hz = clk_get_rate(bs->clk);
if (!clk_hz) {
dev_err(&pdev->dev, "clock returns 0 Hz\n");
err = -ENODEV;
goto out_clk_disable;
}
/* reset SPI-HW block */
bcm2835aux_spi_reset_hw(bs);
err = devm_request_irq(&pdev->dev, bs->irq,
bcm2835aux_spi_interrupt,
IRQF_SHARED,
dev_name(&pdev->dev), master);
if (err) {
dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
goto out_clk_disable;
}
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 bcm2835aux_spi_remove(struct platform_device *pdev)
{
struct spi_master *master = platform_get_drvdata(pdev);
struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
bcm2835aux_spi_reset_hw(bs);
/* disable the HW block by releasing the clock */
clk_disable_unprepare(bs->clk);
return 0;
}
static const struct of_device_id bcm2835aux_spi_match[] = {
{ .compatible = "brcm,bcm2835-aux-spi", },
{}
};
MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match);
static struct platform_driver bcm2835aux_spi_driver = {
.driver = {
.name = "spi-bcm2835aux",
.of_match_table = bcm2835aux_spi_match,
},
.probe = bcm2835aux_spi_probe,
.remove = bcm2835aux_spi_remove,
};
module_platform_driver(bcm2835aux_spi_driver);
MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux");
MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
MODULE_LICENSE("GPL v2");
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