// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 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
*/
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/debugfs.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/platform_device.h>
#include <linux/regmap.h>
#include <linux/spi/spi.h>
#include <linux/spinlock.h>
/* define polling limits */
static unsigned int polling_limit_us = 30;
module_param(polling_limit_us, uint, 0664);
MODULE_PARM_DESC(polling_limit_us,
"time in us to run a transfer in polling mode - if zero no polling is used\n");
/*
* 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_IN_RISING 0x00000400
#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200
#define BCM2835_AUX_SPI_CNTL0_OUT_RISING 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_TXEMPTY 0x00000080
#define BCM2835_AUX_SPI_CNTL1_IDLE 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
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;
u64 count_transfer_polling;
u64 count_transfer_irq;
u64 count_transfer_irq_after_poll;
struct dentry *debugfs_dir;
};
#if defined(CONFIG_DEBUG_FS)
static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs,
const char *dname)
{
char name[64];
struct dentry *dir;
/* get full name */
snprintf(name, sizeof(name), "spi-bcm2835aux-%s", dname);
/* the base directory */
dir = debugfs_create_dir(name, NULL);
bs->debugfs_dir = dir;
/* the counters */
debugfs_create_u64("count_transfer_polling", 0444, dir,
&bs->count_transfer_polling);
debugfs_create_u64("count_transfer_irq", 0444, dir,
&bs->count_transfer_irq);
debugfs_create_u64("count_transfer_irq_after_poll", 0444, dir,
&bs->count_transfer_irq_after_poll);
}
static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs)
{
debugfs_remove_recursive(bs->debugfs_dir);
bs->debugfs_dir = NULL;
}
#else
static void bcm2835aux_debugfs_create(struct bcm2835aux_spi *bs,
const char *dname)
{
}
static void bcm2835aux_debugfs_remove(struct bcm2835aux_spi *bs)
{
}
#endif /* CONFIG_DEBUG_FS */
static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned int reg)
{
return readl(bs->regs + reg);
}
static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned int 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 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 void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs)
{
u32 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT);
/* check if we have data to read */
for (; bs->rx_len && (stat & BCM2835_AUX_SPI_STAT_RX_LVL);
stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT))
bcm2835aux_rd_fifo(bs);
/* 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);
}
}
static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
{
struct spi_controller *host = dev_id;
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
/* IRQ may be shared, so return if our interrupts are disabled */
if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) &
(BCM2835_AUX_SPI_CNTL1_TXEMPTY | BCM2835_AUX_SPI_CNTL1_IDLE)))
return IRQ_NONE;
/* do common fifo handling */
bcm2835aux_spi_transfer_helper(bs);
if (!bs->tx_len) {
/* disable tx fifo empty interrupt */
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
BCM2835_AUX_SPI_CNTL1_IDLE);
}
/* and if rx_len is 0 then disable interrupts and wake up completion */
if (!bs->rx_len) {
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
spi_finalize_current_transfer(host);
}
return IRQ_HANDLED;
}
static int __bcm2835aux_spi_transfer_one_irq(struct spi_controller *host,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
/* 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_controller *host,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
/* update statistics */
bs->count_transfer_irq++;
/* 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(host, spi, tfr);
}
static int bcm2835aux_spi_transfer_one_poll(struct spi_controller *host,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
unsigned long timeout;
/* update statistics */
bs->count_transfer_polling++;
/* 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 to at least 2 jiffies */
timeout = jiffies + 2 + HZ * polling_limit_us / 1000000;
/* loop until finished the transfer */
while (bs->rx_len) {
/* do common fifo handling */
bcm2835aux_spi_transfer_helper(bs);
/* 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 */
bs->count_transfer_irq_after_poll++;
return __bcm2835aux_spi_transfer_one_irq(host,
spi, tfr);
}
}
/* and return without waiting for completion */
return 0;
}
static int bcm2835aux_spi_transfer_one(struct spi_controller *host,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
unsigned long spi_hz, clk_hz, speed;
unsigned long hz_per_byte, byte_limit;
/* 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
*/
/* 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;
}
/* mask out old speed from previous spi_transfer */
bs->cntl[0] &= ~(BCM2835_AUX_SPI_CNTL0_SPEED);
/* set the new speed */
bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;
tfr->effective_speed_hz = clk_hz / (2 * (speed + 1));
/* 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 2 idle clocks cycles after each chunk getting
* transferred - in our case the chunk size is 3 bytes, so we
* approximate this by 9 cycles/byte. This is used to find the number
* of Hz per byte per polling limit. E.g., we can transfer 1 byte in
* 30 µs per 300,000 Hz of bus clock.
*/
hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0;
byte_limit = hz_per_byte ? tfr->effective_speed_hz / hz_per_byte : 1;
/* run in polling mode for short transfers */
if (tfr->len < byte_limit)
return bcm2835aux_spi_transfer_one_poll(host, spi, tfr);
/* run in interrupt mode for all others */
return bcm2835aux_spi_transfer_one_irq(host, spi, tfr);
}
static int bcm2835aux_spi_prepare_message(struct spi_controller *host,
struct spi_message *msg)
{
struct spi_device *spi = msg->spi;
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
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;
/* handle all the modes */
if (spi->mode & SPI_CPOL) {
bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL;
bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_OUT_RISING;
} else {
bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_IN_RISING;
}
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
return 0;
}
static int bcm2835aux_spi_unprepare_message(struct spi_controller *host,
struct spi_message *msg)
{
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
bcm2835aux_spi_reset_hw(bs);
return 0;
}
static void bcm2835aux_spi_handle_err(struct spi_controller *host,
struct spi_message *msg)
{
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
bcm2835aux_spi_reset_hw(bs);
}
static int bcm2835aux_spi_setup(struct spi_device *spi)
{
/* sanity check for native cs */
if (spi->mode & SPI_NO_CS)
return 0;
if (spi_get_csgpiod(spi, 0))
return 0;
/* for dt-backwards compatibility: only support native on CS0
* known things not supported with broken native CS:
* * multiple chip-selects: cs0-cs2 are all
* simultaniously asserted whenever there is a transfer
* this even includes SPI_NO_CS
* * SPI_CS_HIGH: cs are always asserted low
* * cs_change: cs is deasserted after each spi_transfer
* * cs_delay_usec: cs is always deasserted one SCK cycle
* after the last transfer
* probably more...
*/
dev_warn(&spi->dev,
"Native CS is not supported - please configure cs-gpio in device-tree\n");
if (spi_get_chipselect(spi, 0) == 0)
return 0;
dev_warn(&spi->dev, "Native CS is not working for cs > 0\n");
return -EINVAL;
}
static int bcm2835aux_spi_probe(struct platform_device *pdev)
{
struct spi_controller *host;
struct bcm2835aux_spi *bs;
unsigned long clk_hz;
int err;
host = devm_spi_alloc_host(&pdev->dev, sizeof(*bs));
if (!host)
return -ENOMEM;
platform_set_drvdata(pdev, host);
host->mode_bits = (SPI_CPOL | SPI_CS_HIGH | SPI_NO_CS);
host->bits_per_word_mask = SPI_BPW_MASK(8);
/* even though the driver never officially supported native CS
* allow a single native CS for legacy DT support purposes when
* no cs-gpio is configured.
* Known limitations for native cs are:
* * multiple chip-selects: cs0-cs2 are all simultaniously asserted
* whenever there is a transfer - this even includes SPI_NO_CS
* * SPI_CS_HIGH: is ignores - cs are always asserted low
* * cs_change: cs is deasserted after each spi_transfer
* * cs_delay_usec: cs is always deasserted one SCK cycle after
* a spi_transfer
*/
host->num_chipselect = 1;
host->setup = bcm2835aux_spi_setup;
host->transfer_one = bcm2835aux_spi_transfer_one;
host->handle_err = bcm2835aux_spi_handle_err;
host->prepare_message = bcm2835aux_spi_prepare_message;
host->unprepare_message = bcm2835aux_spi_unprepare_message;
host->dev.of_node = pdev->dev.of_node;
host->use_gpio_descriptors = true;
bs = spi_controller_get_devdata(host);
/* the main area */
bs->regs = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(bs->regs))
return PTR_ERR(bs->regs);
bs->clk = devm_clk_get_enabled(&pdev->dev, NULL);
if (IS_ERR(bs->clk)) {
err = PTR_ERR(bs->clk);
dev_err(&pdev->dev, "could not get clk: %d\n", err);
return err;
}
bs->irq = platform_get_irq(pdev, 0);
if (bs->irq < 0)
return bs->irq;
/* 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");
return -ENODEV;
}
/* 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), host);
if (err) {
dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
return err;
}
err = spi_register_controller(host);
if (err) {
dev_err(&pdev->dev, "could not register SPI host: %d\n", err);
return err;
}
bcm2835aux_debugfs_create(bs, dev_name(&pdev->dev));
return 0;
}
static void bcm2835aux_spi_remove(struct platform_device *pdev)
{
struct spi_controller *host = platform_get_drvdata(pdev);
struct bcm2835aux_spi *bs = spi_controller_get_devdata(host);
bcm2835aux_debugfs_remove(bs);
spi_unregister_controller(host);
bcm2835aux_spi_reset_hw(bs);
}
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_new = bcm2835aux_spi_remove,
};
module_platform_driver(bcm2835aux_spi_driver);
MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux");
MODULE_AUTHOR("Martin Sperl <[email protected]>");
MODULE_LICENSE("GPL");
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