Re: [PATCH] i2c: add Cadence i2c host controller support

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On Tue, May 10, 2022 at 03:04:14PM +0200, Matthias Fend wrote:
> Add a driver to support the Cadence I2C host controller found in Zynq
> UltraScale+ MPSoCs.
> 
> Signed-off-by: Matthias Fend <matthias.fend@xxxxxxxxx>
> ---
>  drivers/i2c/busses/Kconfig       |   8 +
>  drivers/i2c/busses/Makefile      |   1 +
>  drivers/i2c/busses/i2c-cadence.c | 453 +++++++++++++++++++++++++++++++
>  3 files changed, 462 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-cadence.c

Applied, thanks

Sascha

> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index d4e74552b..58f865606 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -70,4 +70,12 @@ config I2C_RK3X
>  	  Say Y here to include support for the I2C adapter in Rockchip RK3xxx
>  	  SoCs.
>  
> +config I2C_CADENCE
> +	bool "Cadence I2C adapter"
> +	depends on HAVE_CLK
> +	depends on ARCH_ZYNQMP || COMPILE_TEST
> +	help
> +	  Say Y here to include support for the Cadence I2C host controller found
> +	  in Zynq UltraScale+ MPSoCs.
> +
>  endmenu
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index d6273f3d8..a8661f605 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
>  obj-$(CONFIG_I2C_DESIGNWARE)	+= i2c-designware.o
>  obj-$(CONFIG_I2C_STM32)		+= i2c-stm32.o
>  obj-$(CONFIG_I2C_RK3X)		+= i2c-rockchip.o
> +obj-$(CONFIG_I2C_CADENCE)	+= i2c-cadence.o
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
> new file mode 100644
> index 000000000..5537efff2
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -0,0 +1,453 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * I2C bus driver for the Cadence I2C host controller (master only).
> + *
> + * Partly based on the driver in the Linux kernel
> + *    Copyright (C) 2009 - 2014 Xilinx, Inc.
> + *
> + * Copyright (C) 2022 Matthias Fend <matthias.fend@xxxxxxxxx>
> + */
> +
> +#include <common.h>
> +#include <i2c/i2c.h>
> +#include <linux/iopoll.h>
> +#include <errno.h>
> +#include <linux/err.h>
> +#include <driver.h>
> +#include <io.h>
> +#include <linux/clk.h>
> +#include <regmap.h>
> +
> +struct __packed i2c_regs {
> +	u32 control;
> +	u32 status;
> +	u32 address;
> +	u32 data;
> +	u32 interrupt_status;
> +	u32 transfer_size;
> +	u32 slave_mon_pause;
> +	u32 time_out;
> +	u32 interrupt_mask;
> +	u32 interrupt_enable;
> +	u32 interrupt_disable;
> +	u32 glitch_filter;
> +};
> +
> +/* Control register fields */
> +#define CDNS_I2C_CONTROL_RW		BIT(0)
> +#define CDNS_I2C_CONTROL_MS		BIT(1)
> +#define CDNS_I2C_CONTROL_NEA		BIT(2)
> +#define CDNS_I2C_CONTROL_ACKEN		BIT(3)
> +#define CDNS_I2C_CONTROL_HOLD		BIT(4)
> +#define CDNS_I2C_CONTROL_SLVMON		BIT(5)
> +#define CDNS_I2C_CONTROL_CLR_FIFO	BIT(6)
> +#define CDNS_I2C_CONTROL_DIV_B_SHIFT	8
> +#define CDNS_I2C_CONTROL_DIV_B_MASK	(0x3F << CDNS_I2C_CONTROL_DIV_B_SHIFT)
> +#define CDNS_I2C_CONTROL_DIV_A_SHIFT	14
> +#define CDNS_I2C_CONTROL_DIV_A_MASK	(0x03 << CDNS_I2C_CONTROL_DIV_A_SHIFT)
> +
> +#define CDNS_I2C_CONTROL_DIV_B_MAX	64
> +#define CDNS_I2C_CONTROL_DIV_A_MAX	4
> +
> +/* Status register fields */
> +#define CDNS_I2C_STATUS_RXRW		BIT(3)
> +#define CDNS_I2C_STATUS_RXDV		BIT(5)
> +#define CDNS_I2C_STATUS_TXDV		BIT(6)
> +#define CDNS_I2C_STATUS_RXOVF		BIT(7)
> +#define CDNS_I2C_STATUS_BA		BIT(8)
> +
> +/* Address register fields */
> +#define CDNS_I2C_ADDRESS_MASK		0x3FF
> +
> +/* Interrupt register fields */
> +#define CDNS_I2C_INTERRUPT_COMP		BIT(0)
> +#define CDNS_I2C_INTERRUPT_DATA		BIT(1)
> +#define CDNS_I2C_INTERRUPT_NACK		BIT(2)
> +#define CDNS_I2C_INTERRUPT_TO		BIT(3)
> +#define CDNS_I2C_INTERRUPT_SLVRDY	BIT(4)
> +#define CDNS_I2C_INTERRUPT_RXOVF	BIT(5)
> +#define CDNS_I2C_INTERRUPT_TXOVF	BIT(6)
> +#define CDNS_I2C_INTERRUPT_RXUNF	BIT(7)
> +#define CDNS_I2C_INTERRUPT_ARBLOST	BIT(9)
> +
> +#define CDNS_I2C_INTERRUPTS_MASK_MASTER	(CDNS_I2C_INTERRUPT_COMP  | \
> +					CDNS_I2C_INTERRUPT_DATA   | \
> +					CDNS_I2C_INTERRUPT_NACK   | \
> +					CDNS_I2C_INTERRUPT_RXOVF  | \
> +					CDNS_I2C_INTERRUPT_TXOVF  | \
> +					CDNS_I2C_INTERRUPT_RXUNF  | \
> +					CDNS_I2C_INTERRUPT_ARBLOST)
> +
> +#define CDNS_I2C_INTERRUPTS_MASK_ALL	(CDNS_I2C_INTERRUPT_COMP  | \
> +					CDNS_I2C_INTERRUPT_DATA   | \
> +					CDNS_I2C_INTERRUPT_NACK   | \
> +					CDNS_I2C_INTERRUPT_TO     | \
> +					CDNS_I2C_INTERRUPT_SLVRDY | \
> +					CDNS_I2C_INTERRUPT_RXOVF  | \
> +					CDNS_I2C_INTERRUPT_TXOVF  | \
> +					CDNS_I2C_INTERRUPT_RXUNF  | \
> +					CDNS_I2C_INTERRUPT_ARBLOST)
> +
> +#define CDNS_I2C_FIFO_DEPTH		16
> +#define CDNS_I2C_TRANSFER_SIZE_MAX	255
> +#define CDNS_I2C_TRANSFER_SIZE		(CDNS_I2C_TRANSFER_SIZE_MAX - 3)
> +
> +#define I2C_TIMEOUT_US			(100 * USEC_PER_MSEC)
> +
> +struct cdns_i2c {
> +	struct i2c_adapter adapter;
> +	struct clk *clk;
> +	struct i2c_regs *regs;
> +	bool bus_hold_flag;
> +};
> +
> +static void cdns_i2c_reset_hardware(struct cdns_i2c *i2c)
> +{
> +	struct i2c_regs *regs = i2c->regs;
> +	u32 regval;
> +
> +	writel(CDNS_I2C_INTERRUPTS_MASK_ALL, &regs->interrupt_disable);
> +
> +	regval = readl(&regs->control);
> +	regval &= ~CDNS_I2C_CONTROL_HOLD;
> +	regval |= CDNS_I2C_CONTROL_CLR_FIFO;
> +	writel(regval, &regs->control);
> +
> +	writel(0xFF, &regs->time_out);
> +
> +	writel(0, &regs->transfer_size);
> +
> +	regval = readl(&regs->interrupt_status);
> +	writel(regval, &regs->interrupt_status);
> +
> +	regval = readl(&regs->status);
> +	writel(regval, &regs->status);
> +
> +	writel(0, &regs->control);
> +}
> +
> +static void cdns_i2c_setup_master(struct cdns_i2c *i2c)
> +{
> +	u32 control;
> +
> +	control = readl(&i2c->regs->control);
> +	control |= CDNS_I2C_CONTROL_MS | CDNS_I2C_CONTROL_ACKEN |
> +		   CDNS_I2C_CONTROL_NEA;
> +	writel(control, &i2c->regs->control);
> +
> +	writel(CDNS_I2C_INTERRUPTS_MASK_MASTER, &i2c->regs->interrupt_enable);
> +}
> +
> +static void cdns_i2c_clear_hold_flag(struct cdns_i2c *i2c)
> +{
> +	u32 control;
> +
> +	control = readl(&i2c->regs->control);
> +	if (control & CDNS_I2C_CONTROL_HOLD)
> +		writel(control & ~CDNS_I2C_CONTROL_HOLD, &i2c->regs->control);
> +}
> +
> +static bool cdns_i2c_is_busy(struct cdns_i2c *i2c)
> +{
> +	return readl(&i2c->regs->status) & CDNS_I2C_STATUS_BA;
> +}
> +
> +static int cdns_i2c_hw_error(struct cdns_i2c *i2c)
> +{
> +	u32 isr_status;
> +
> +	isr_status = readl(&i2c->regs->interrupt_status);
> +
> +	if (isr_status & CDNS_I2C_INTERRUPT_NACK)
> +		return -EREMOTEIO;
> +
> +	if (isr_status &
> +	    (CDNS_I2C_INTERRUPT_ARBLOST | CDNS_I2C_INTERRUPT_RXOVF))
> +		return -EAGAIN;
> +
> +	return 0;
> +}
> +
> +static int cdns_i2c_wait_for_completion(struct cdns_i2c *i2c)
> +{
> +	int err;
> +	u32 isr_status;
> +	const u32 isr_mask =
> +		(CDNS_I2C_INTERRUPT_COMP | CDNS_I2C_INTERRUPT_NACK |
> +		 CDNS_I2C_INTERRUPT_ARBLOST);
> +
> +	err = readl_poll_timeout(&i2c->regs->interrupt_status, isr_status,
> +				 isr_status & isr_mask, I2C_TIMEOUT_US);
> +
> +	if (err)
> +		return -ETIMEDOUT;
> +
> +	return cdns_i2c_hw_error(i2c);
> +}
> +
> +/*
> + * Find best clock divisors
> + *
> + * f = finput / (22 x (div_a + 1) x (div_b + 1))
> + */
> +static int cdns_i2c_calc_divs(u32 *f, u32 input_clk, u32 *a, u32 *b)
> +{
> +	ulong fscl = *f, best_fscl = *f, actual_fscl, temp;
> +	uint div_a, div_b, calc_div_a = 0, calc_div_b = 0;
> +	uint last_error, current_error;
> +
> +	temp = input_clk / (22 * fscl);
> +
> +	if (!temp ||
> +	    (temp > (CDNS_I2C_CONTROL_DIV_A_MAX * CDNS_I2C_CONTROL_DIV_B_MAX)))
> +		return -EINVAL;
> +
> +	last_error = -1;
> +	for (div_a = 0; div_a < CDNS_I2C_CONTROL_DIV_A_MAX; div_a++) {
> +		div_b = DIV_ROUND_UP(input_clk, 22 * fscl * (div_a + 1));
> +
> +		if ((div_b < 1) || (div_b > CDNS_I2C_CONTROL_DIV_B_MAX))
> +			continue;
> +		div_b--;
> +
> +		actual_fscl = input_clk / (22 * (div_a + 1) * (div_b + 1));
> +
> +		if (actual_fscl > fscl)
> +			continue;
> +
> +		current_error = ((actual_fscl > fscl) ? (actual_fscl - fscl) :
> +							(fscl - actual_fscl));
> +
> +		if (last_error > current_error) {
> +			calc_div_a = div_a;
> +			calc_div_b = div_b;
> +			best_fscl = actual_fscl;
> +			last_error = current_error;
> +		}
> +	}
> +
> +	*a = calc_div_a;
> +	*b = calc_div_b;
> +	*f = best_fscl;
> +
> +	return 0;
> +}
> +
> +static int cdns_i2c_set_clk(struct cdns_i2c *i2c, u32 scl_rate)
> +{
> +	u32 i2c_rate;
> +	u32 control;
> +	u32 div_a, div_b;
> +	int err;
> +
> +	i2c_rate = clk_get_rate(i2c->clk);
> +
> +	err = cdns_i2c_calc_divs(&scl_rate, i2c_rate, &div_a, &div_b);
> +	if (err)
> +		return err;
> +
> +	control = readl(&i2c->regs->control);
> +	control &= ~(CDNS_I2C_CONTROL_DIV_B_MASK | CDNS_I2C_CONTROL_DIV_A_MASK);
> +	control |= (div_b << CDNS_I2C_CONTROL_DIV_B_SHIFT) |
> +		   (div_a << CDNS_I2C_CONTROL_DIV_A_SHIFT);
> +	writel(control, &i2c->regs->control);
> +
> +	return err;
> +}
> +
> +static int cdns_i2c_read(struct cdns_i2c *i2c, uchar chip, uchar *buf,
> +			 uint buf_len)
> +{
> +	struct i2c_regs *regs = i2c->regs;
> +	u32 control;
> +	int err;
> +
> +	control = readl(&regs->control);
> +	control |= CDNS_I2C_CONTROL_RW | CDNS_I2C_CONTROL_CLR_FIFO;
> +	if (i2c->bus_hold_flag || (buf_len > CDNS_I2C_FIFO_DEPTH))
> +		control |= CDNS_I2C_CONTROL_HOLD;
> +	writel(control, &regs->control);
> +
> +	do {
> +		uint bytes_to_receive;
> +		u32 isr_status;
> +		u64 start_time;
> +
> +		isr_status = readl(&regs->interrupt_status);
> +		writel(isr_status, &regs->interrupt_status);
> +
> +		if (buf_len > CDNS_I2C_TRANSFER_SIZE)
> +			bytes_to_receive = CDNS_I2C_TRANSFER_SIZE;
> +		else
> +			bytes_to_receive = buf_len;
> +
> +		buf_len -= bytes_to_receive;
> +
> +		writel(bytes_to_receive, &regs->transfer_size);
> +		writel(chip & CDNS_I2C_ADDRESS_MASK, &regs->address);
> +
> +		start_time = get_time_ns();
> +		while (bytes_to_receive) {
> +			err = cdns_i2c_hw_error(i2c);
> +			if (err)
> +				goto i2c_exit;
> +
> +			if (is_timeout(start_time,
> +				       (I2C_TIMEOUT_US * USECOND))) {
> +				err = -ETIMEDOUT;
> +				goto i2c_exit;
> +			}
> +
> +			if (readl(&regs->status) & CDNS_I2C_STATUS_RXDV) {
> +				*buf++ = readl(&regs->data);
> +				bytes_to_receive--;
> +			}
> +		}
> +
> +	} while (buf_len);
> +
> +	err = cdns_i2c_wait_for_completion(i2c);
> +
> +i2c_exit:
> +	if (!i2c->bus_hold_flag)
> +		cdns_i2c_clear_hold_flag(i2c);
> +
> +	return err;
> +}
> +
> +static int cdns_i2c_write(struct cdns_i2c *i2c, uchar chip, uchar *buf,
> +			  uint buf_len)
> +{
> +	struct i2c_regs *regs = i2c->regs;
> +	u32 control;
> +	u32 isr_status;
> +	bool start_transfer;
> +	int err;
> +
> +	control = readl(&regs->control);
> +	control &= ~CDNS_I2C_CONTROL_RW;
> +	control |= CDNS_I2C_CONTROL_CLR_FIFO;
> +	if (i2c->bus_hold_flag || (buf_len > CDNS_I2C_FIFO_DEPTH))
> +		control |= CDNS_I2C_CONTROL_HOLD;
> +	writel(control, &regs->control);
> +
> +	isr_status = readl(&regs->interrupt_status);
> +	writel(isr_status, &regs->interrupt_status);
> +
> +	start_transfer = true;
> +	do {
> +		uint bytes_to_send;
> +
> +		bytes_to_send =
> +			CDNS_I2C_FIFO_DEPTH - readl(&regs->transfer_size);
> +
> +		if (buf_len < bytes_to_send)
> +			bytes_to_send = buf_len;
> +
> +		buf_len -= bytes_to_send;
> +
> +		while (bytes_to_send--)
> +			writel(*buf++, &regs->data);
> +
> +		if (start_transfer) {
> +			writel(chip & CDNS_I2C_ADDRESS_MASK, &regs->address);
> +			start_transfer = false;
> +		}
> +
> +		err = cdns_i2c_wait_for_completion(i2c);
> +		if (err)
> +			goto i2c_exit;
> +
> +	} while (buf_len);
> +
> +i2c_exit:
> +	if (!i2c->bus_hold_flag)
> +		cdns_i2c_clear_hold_flag(i2c);
> +
> +	return err;
> +}
> +
> +static int cdns_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msg,
> +			 int nmsgs)
> +{
> +	struct cdns_i2c *i2c = container_of(adapter, struct cdns_i2c, adapter);
> +	int i;
> +	int err;
> +
> +	if (cdns_i2c_is_busy(i2c))
> +		return -EBUSY;
> +
> +	for (i = 0; i < nmsgs; i++) {
> +		i2c->bus_hold_flag = i < (nmsgs - 1);
> +
> +		if (msg->flags & I2C_M_RD) {
> +			err = cdns_i2c_read(i2c, msg->addr, msg->buf, msg->len);
> +		} else {
> +			err = cdns_i2c_write(i2c, msg->addr, msg->buf,
> +					     msg->len);
> +		}
> +
> +		if (err)
> +			return err;
> +
> +		msg++;
> +	}
> +
> +	return nmsgs;
> +}
> +
> +static int cdns_i2c_probe(struct device_d *dev)
> +{
> +	struct device_node *np = dev->device_node;
> +	struct resource *iores;
> +	struct cdns_i2c *i2c;
> +	u32 bitrate;
> +	int err;
> +
> +	iores = dev_request_mem_resource(dev, 0);
> +	if (IS_ERR(iores))
> +		return PTR_ERR(iores);
> +
> +	i2c = xzalloc(sizeof(*i2c));
> +
> +	dev->priv = i2c;
> +	i2c->regs = IOMEM(iores->start);
> +
> +	i2c->clk = clk_get(dev, NULL);
> +	if (IS_ERR(i2c->clk))
> +		return PTR_ERR(i2c->clk);
> +
> +	err = clk_enable(i2c->clk);
> +	if (err)
> +		return err;
> +
> +	i2c->adapter.master_xfer = cdns_i2c_xfer;
> +	i2c->adapter.nr = dev->id;
> +	i2c->adapter.dev.parent = dev;
> +	i2c->adapter.dev.device_node = np;
> +
> +	cdns_i2c_reset_hardware(i2c);
> +
> +	bitrate = 100000;
> +	of_property_read_u32(np, "clock-frequency", &bitrate);
> +
> +	err = cdns_i2c_set_clk(i2c, bitrate);
> +	if (err)
> +		return err;
> +
> +	cdns_i2c_setup_master(i2c);
> +
> +	return i2c_add_numbered_adapter(&i2c->adapter);
> +}
> +
> +static const struct of_device_id cdns_i2c_match[] = {
> +	{ .compatible = "cdns,i2c-r1p14" },
> +	{},
> +};
> +
> +static struct driver_d cdns_i2c_driver = {
> +	.name = "cdns-i2c",
> +	.of_compatible = cdns_i2c_match,
> +	.probe = cdns_i2c_probe,
> +};
> +coredevice_platform_driver(cdns_i2c_driver);
> -- 
> 2.25.1
> 
> 
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