https://github.com/torvalds/linux
Tip revision: b90cb1053190353cc30f0fef0ef1f378ccc063c5 authored by Linus Torvalds on 28 August 2022, 22:05:29 UTC
Linux 6.0-rc3
Linux 6.0-rc3
Tip revision: b90cb10
i2c-bcm2835.c
// SPDX-License-Identifier: GPL-2.0
/*
* BCM2835 master mode driver
*/
#include <linux/clk.h>
#include <linux/clkdev.h>
#include <linux/clk-provider.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#define BCM2835_I2C_C 0x0
#define BCM2835_I2C_S 0x4
#define BCM2835_I2C_DLEN 0x8
#define BCM2835_I2C_A 0xc
#define BCM2835_I2C_FIFO 0x10
#define BCM2835_I2C_DIV 0x14
#define BCM2835_I2C_DEL 0x18
/*
* 16-bit field for the number of SCL cycles to wait after rising SCL
* before deciding the slave is not responding. 0 disables the
* timeout detection.
*/
#define BCM2835_I2C_CLKT 0x1c
#define BCM2835_I2C_C_READ BIT(0)
#define BCM2835_I2C_C_CLEAR BIT(4) /* bits 4 and 5 both clear */
#define BCM2835_I2C_C_ST BIT(7)
#define BCM2835_I2C_C_INTD BIT(8)
#define BCM2835_I2C_C_INTT BIT(9)
#define BCM2835_I2C_C_INTR BIT(10)
#define BCM2835_I2C_C_I2CEN BIT(15)
#define BCM2835_I2C_S_TA BIT(0)
#define BCM2835_I2C_S_DONE BIT(1)
#define BCM2835_I2C_S_TXW BIT(2)
#define BCM2835_I2C_S_RXR BIT(3)
#define BCM2835_I2C_S_TXD BIT(4)
#define BCM2835_I2C_S_RXD BIT(5)
#define BCM2835_I2C_S_TXE BIT(6)
#define BCM2835_I2C_S_RXF BIT(7)
#define BCM2835_I2C_S_ERR BIT(8)
#define BCM2835_I2C_S_CLKT BIT(9)
#define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */
#define BCM2835_I2C_FEDL_SHIFT 16
#define BCM2835_I2C_REDL_SHIFT 0
#define BCM2835_I2C_CDIV_MIN 0x0002
#define BCM2835_I2C_CDIV_MAX 0xFFFE
struct bcm2835_i2c_dev {
struct device *dev;
void __iomem *regs;
int irq;
struct i2c_adapter adapter;
struct completion completion;
struct i2c_msg *curr_msg;
struct clk *bus_clk;
int num_msgs;
u32 msg_err;
u8 *msg_buf;
size_t msg_buf_remaining;
};
static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
u32 reg, u32 val)
{
writel(val, i2c_dev->regs + reg);
}
static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
{
return readl(i2c_dev->regs + reg);
}
#define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
struct clk_bcm2835_i2c {
struct clk_hw hw;
struct bcm2835_i2c_dev *i2c_dev;
};
static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
unsigned long parent_rate)
{
u32 divider = DIV_ROUND_UP(parent_rate, rate);
/*
* Per the datasheet, the register is always interpreted as an even
* number, by rounding down. In other words, the LSB is ignored. So,
* if the LSB is set, increment the divider to avoid any issue.
*/
if (divider & 1)
divider++;
if ((divider < BCM2835_I2C_CDIV_MIN) ||
(divider > BCM2835_I2C_CDIV_MAX))
return -EINVAL;
return divider;
}
static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
u32 redl, fedl;
u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
if (divider == -EINVAL)
return -EINVAL;
bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider);
/*
* Number of core clocks to wait after falling edge before
* outputting the next data bit. Note that both FEDL and REDL
* can't be greater than CDIV/2.
*/
fedl = max(divider / 16, 1u);
/*
* Number of core clocks to wait after rising edge before
* sampling the next incoming data bit.
*/
redl = max(divider / 4, 1u);
bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL,
(fedl << BCM2835_I2C_FEDL_SHIFT) |
(redl << BCM2835_I2C_REDL_SHIFT));
return 0;
}
static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate)
{
u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
return DIV_ROUND_UP(*parent_rate, divider);
}
static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
return DIV_ROUND_UP(parent_rate, divider);
}
static const struct clk_ops clk_bcm2835_i2c_ops = {
.set_rate = clk_bcm2835_i2c_set_rate,
.round_rate = clk_bcm2835_i2c_round_rate,
.recalc_rate = clk_bcm2835_i2c_recalc_rate,
};
static struct clk *bcm2835_i2c_register_div(struct device *dev,
struct clk *mclk,
struct bcm2835_i2c_dev *i2c_dev)
{
struct clk_init_data init;
struct clk_bcm2835_i2c *priv;
char name[32];
const char *mclk_name;
snprintf(name, sizeof(name), "%s_div", dev_name(dev));
mclk_name = __clk_get_name(mclk);
init.ops = &clk_bcm2835_i2c_ops;
init.name = name;
init.parent_names = (const char* []) { mclk_name };
init.num_parents = 1;
init.flags = 0;
priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
if (priv == NULL)
return ERR_PTR(-ENOMEM);
priv->hw.init = &init;
priv->i2c_dev = i2c_dev;
clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
return devm_clk_register(dev, &priv->hw);
}
static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
{
u32 val;
while (i2c_dev->msg_buf_remaining) {
val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
if (!(val & BCM2835_I2C_S_TXD))
break;
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
*i2c_dev->msg_buf);
i2c_dev->msg_buf++;
i2c_dev->msg_buf_remaining--;
}
}
static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
{
u32 val;
while (i2c_dev->msg_buf_remaining) {
val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
if (!(val & BCM2835_I2C_S_RXD))
break;
*i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
BCM2835_I2C_FIFO);
i2c_dev->msg_buf++;
i2c_dev->msg_buf_remaining--;
}
}
/*
* Repeated Start Condition (Sr)
* The BCM2835 ARM Peripherals datasheet mentions a way to trigger a Sr when it
* talks about reading from a slave with 10 bit address. This is achieved by
* issuing a write, poll the I2CS.TA flag and wait for it to be set, and then
* issue a read.
* A comment in https://github.com/raspberrypi/linux/issues/254 shows how the
* firmware actually does it using polling and says that it's a workaround for
* a problem in the state machine.
* It turns out that it is possible to use the TXW interrupt to know when the
* transfer is active, provided the FIFO has not been prefilled.
*/
static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev)
{
u32 c = BCM2835_I2C_C_ST | BCM2835_I2C_C_I2CEN;
struct i2c_msg *msg = i2c_dev->curr_msg;
bool last_msg = (i2c_dev->num_msgs == 1);
if (!i2c_dev->num_msgs)
return;
i2c_dev->num_msgs--;
i2c_dev->msg_buf = msg->buf;
i2c_dev->msg_buf_remaining = msg->len;
if (msg->flags & I2C_M_RD)
c |= BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
else
c |= BCM2835_I2C_C_INTT;
if (last_msg)
c |= BCM2835_I2C_C_INTD;
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
}
static void bcm2835_i2c_finish_transfer(struct bcm2835_i2c_dev *i2c_dev)
{
i2c_dev->curr_msg = NULL;
i2c_dev->num_msgs = 0;
i2c_dev->msg_buf = NULL;
i2c_dev->msg_buf_remaining = 0;
}
/*
* Note about I2C_C_CLEAR on error:
* The I2C_C_CLEAR on errors will take some time to resolve -- if you were in
* non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through
* the state machine to send a NACK and a STOP. Since we're setting CLEAR
* without I2CEN, that NACK will be hanging around queued up for next time
* we start the engine.
*/
static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
{
struct bcm2835_i2c_dev *i2c_dev = data;
u32 val, err;
val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
if (err) {
i2c_dev->msg_err = err;
goto complete;
}
if (val & BCM2835_I2C_S_DONE) {
if (!i2c_dev->curr_msg) {
dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
} else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
bcm2835_drain_rxfifo(i2c_dev);
val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
}
if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
i2c_dev->msg_err = BCM2835_I2C_S_LEN;
else
i2c_dev->msg_err = 0;
goto complete;
}
if (val & BCM2835_I2C_S_TXW) {
if (!i2c_dev->msg_buf_remaining) {
i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
goto complete;
}
bcm2835_fill_txfifo(i2c_dev);
if (i2c_dev->num_msgs && !i2c_dev->msg_buf_remaining) {
i2c_dev->curr_msg++;
bcm2835_i2c_start_transfer(i2c_dev);
}
return IRQ_HANDLED;
}
if (val & BCM2835_I2C_S_RXR) {
if (!i2c_dev->msg_buf_remaining) {
i2c_dev->msg_err = val | BCM2835_I2C_S_LEN;
goto complete;
}
bcm2835_drain_rxfifo(i2c_dev);
return IRQ_HANDLED;
}
return IRQ_NONE;
complete:
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, BCM2835_I2C_S_CLKT |
BCM2835_I2C_S_ERR | BCM2835_I2C_S_DONE);
complete(&i2c_dev->completion);
return IRQ_HANDLED;
}
static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
int num)
{
struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
unsigned long time_left;
int i;
for (i = 0; i < (num - 1); i++)
if (msgs[i].flags & I2C_M_RD) {
dev_warn_once(i2c_dev->dev,
"only one read message supported, has to be last\n");
return -EOPNOTSUPP;
}
i2c_dev->curr_msg = msgs;
i2c_dev->num_msgs = num;
reinit_completion(&i2c_dev->completion);
bcm2835_i2c_start_transfer(i2c_dev);
time_left = wait_for_completion_timeout(&i2c_dev->completion,
adap->timeout);
bcm2835_i2c_finish_transfer(i2c_dev);
if (!time_left) {
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
BCM2835_I2C_C_CLEAR);
dev_err(i2c_dev->dev, "i2c transfer timed out\n");
return -ETIMEDOUT;
}
if (!i2c_dev->msg_err)
return num;
dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
return -EREMOTEIO;
return -EIO;
}
static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}
static const struct i2c_algorithm bcm2835_i2c_algo = {
.master_xfer = bcm2835_i2c_xfer,
.functionality = bcm2835_i2c_func,
};
/*
* The BCM2835 was reported to have problems with clock stretching:
* https://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
* https://www.raspberrypi.org/forums/viewtopic.php?p=146272
*/
static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
.flags = I2C_AQ_NO_CLK_STRETCH,
};
static int bcm2835_i2c_probe(struct platform_device *pdev)
{
struct bcm2835_i2c_dev *i2c_dev;
struct resource *mem;
int ret;
struct i2c_adapter *adap;
struct clk *mclk;
u32 bus_clk_rate;
i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
if (!i2c_dev)
return -ENOMEM;
platform_set_drvdata(pdev, i2c_dev);
i2c_dev->dev = &pdev->dev;
init_completion(&i2c_dev->completion);
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
if (IS_ERR(i2c_dev->regs))
return PTR_ERR(i2c_dev->regs);
mclk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(mclk))
return dev_err_probe(&pdev->dev, PTR_ERR(mclk),
"Could not get clock\n");
i2c_dev->bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);
if (IS_ERR(i2c_dev->bus_clk)) {
dev_err(&pdev->dev, "Could not register clock\n");
return PTR_ERR(i2c_dev->bus_clk);
}
ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
&bus_clk_rate);
if (ret < 0) {
dev_warn(&pdev->dev,
"Could not read clock-frequency property\n");
bus_clk_rate = I2C_MAX_STANDARD_MODE_FREQ;
}
ret = clk_set_rate_exclusive(i2c_dev->bus_clk, bus_clk_rate);
if (ret < 0) {
dev_err(&pdev->dev, "Could not set clock frequency\n");
return ret;
}
ret = clk_prepare_enable(i2c_dev->bus_clk);
if (ret) {
dev_err(&pdev->dev, "Couldn't prepare clock");
goto err_put_exclusive_rate;
}
i2c_dev->irq = platform_get_irq(pdev, 0);
if (i2c_dev->irq < 0) {
ret = i2c_dev->irq;
goto err_disable_unprepare_clk;
}
ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
dev_name(&pdev->dev), i2c_dev);
if (ret) {
dev_err(&pdev->dev, "Could not request IRQ\n");
goto err_disable_unprepare_clk;
}
adap = &i2c_dev->adapter;
i2c_set_adapdata(adap, i2c_dev);
adap->owner = THIS_MODULE;
adap->class = I2C_CLASS_DEPRECATED;
snprintf(adap->name, sizeof(adap->name), "bcm2835 (%s)",
of_node_full_name(pdev->dev.of_node));
adap->algo = &bcm2835_i2c_algo;
adap->dev.parent = &pdev->dev;
adap->dev.of_node = pdev->dev.of_node;
adap->quirks = of_device_get_match_data(&pdev->dev);
/*
* Disable the hardware clock stretching timeout. SMBUS
* specifies a limit for how long the device can stretch the
* clock, but core I2C doesn't.
*/
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_CLKT, 0);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
ret = i2c_add_adapter(adap);
if (ret)
goto err_free_irq;
return 0;
err_free_irq:
free_irq(i2c_dev->irq, i2c_dev);
err_disable_unprepare_clk:
clk_disable_unprepare(i2c_dev->bus_clk);
err_put_exclusive_rate:
clk_rate_exclusive_put(i2c_dev->bus_clk);
return ret;
}
static int bcm2835_i2c_remove(struct platform_device *pdev)
{
struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
clk_rate_exclusive_put(i2c_dev->bus_clk);
clk_disable_unprepare(i2c_dev->bus_clk);
free_irq(i2c_dev->irq, i2c_dev);
i2c_del_adapter(&i2c_dev->adapter);
return 0;
}
static const struct of_device_id bcm2835_i2c_of_match[] = {
{ .compatible = "brcm,bcm2711-i2c" },
{ .compatible = "brcm,bcm2835-i2c", .data = &bcm2835_i2c_quirks },
{},
};
MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
static struct platform_driver bcm2835_i2c_driver = {
.probe = bcm2835_i2c_probe,
.remove = bcm2835_i2c_remove,
.driver = {
.name = "i2c-bcm2835",
.of_match_table = bcm2835_i2c_of_match,
},
};
module_platform_driver(bcm2835_i2c_driver);
MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:i2c-bcm2835");