[v7] i2c: imx: support slave mode for imx I2C driver

From: Biwen Li
Date: Fri Oct 16 2020 - 04:35:10 EST

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From: Biwen Li <biwen.li@xxxxxxx>

The patch supports slave mode for imx I2C driver

Signed-off-by: Biwen Li <biwen.li@xxxxxxx>
---
Change in v7:
- support auto switch mode between master and slave
- enable interrupt when idle in slave mode
- remove #ifdef

Change in v6:
- delete robust logs and comments
- not read status register again in master isr.

Change in v5:
- fix a bug that cannot determine in what mode(master mode or
slave mode)

Change in v4:
- add MACRO CONFIG_I2C_SLAVE to fix compilation issue

Change in v3:
- support layerscape and i.mx platform

Change in v2:
- remove MACRO CONFIG_I2C_SLAVE

drivers/i2c/busses/i2c-imx.c | 213 ++++++++++++++++++++++++++++++++---
1 file changed, 199 insertions(+), 14 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 0ab5381aa012..0d62b09ee967 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -17,6 +17,7 @@
* Copyright (C) 2008 Darius Augulis <darius.augulis at teltonika.lt>
*
* Copyright 2013 Freescale Semiconductor, Inc.
+ * Copyright 2020 NXP
*
*/

@@ -72,6 +73,7 @@
#define IMX_I2C_I2CR 0x02 /* i2c control */
#define IMX_I2C_I2SR 0x03 /* i2c status */
#define IMX_I2C_I2DR 0x04 /* i2c transfer data */
+#define IMX_I2C_IBIC 0x05 /* i2c transfer data */

#define IMX_I2C_REGSHIFT 2
#define VF610_I2C_REGSHIFT 0
@@ -91,6 +93,7 @@
#define I2CR_MSTA 0x20
#define I2CR_IIEN 0x40
#define I2CR_IEN 0x80
+#define IBIC_BIIE 0x80 // Bus idle interrupt enable

/* register bits different operating codes definition:
* 1) I2SR: Interrupt flags clear operation differ between SoCs:
@@ -201,6 +204,7 @@ struct imx_i2c_struct {
struct pinctrl_state *pinctrl_pins_gpio;

struct imx_i2c_dma *dma;
+ struct i2c_client *slave;
};

static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
@@ -277,6 +281,14 @@ static inline unsigned char imx_i2c_read_reg(struct imx_i2c_struct *i2c_imx,
return readb(i2c_imx->base + (reg << i2c_imx->hwdata->regshift));
}

+/* Set up i2c controller register and i2c status register to default value. */
+static void i2c_imx_reset_regs(struct imx_i2c_struct *i2c_imx)
+{
+ imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
+ i2c_imx, IMX_I2C_I2CR);
+ imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
+}
+
/* Functions for DMA support */
static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
dma_addr_t phy_addr)
@@ -614,20 +626,110 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx, bool atomic)
imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
}

+/*
+ * Enable bus idle interrupts
+ * Note: IBIC register will be cleared after disabled i2c module.
+ */
+static void i2c_imx_enable_bus_idle(struct imx_i2c_struct *i2c_imx)
+{
+ unsigned int temp;
+
+ temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_IBIC);
+ temp |= IBIC_BIIE;
+ imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_IBIC);
+}
+
+static void i2c_imx_clr_if_bit(unsigned int status, struct imx_i2c_struct *i2c_imx)
+{
+ status &= ~I2SR_IIF;
+ status |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IIF);
+ imx_i2c_write_reg(status, i2c_imx, IMX_I2C_I2SR);
+}
+
+/* Clear arbitration lost bit */
+static void i2c_imx_clr_al_bit(unsigned int status, struct imx_i2c_struct *i2c_imx)
+{
+ status &= ~I2SR_IAL;
+ status |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IAL);
+ imx_i2c_write_reg(status, i2c_imx, IMX_I2C_I2SR);
+}
+
+static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx,
+ unsigned int status, unsigned int ctl)
+{
+ u8 value;
+
+ if (status & I2SR_IAL) { /* Arbitration lost */
+ i2c_imx_clr_al_bit(status | I2SR_IIF, i2c_imx);
+ } else if (status & I2SR_IAAS) { /* Addressed as a slave */
+ if (status & I2SR_SRW) { /* Master wants to read from us*/
+ dev_dbg(&i2c_imx->adapter.dev, "read requested");
+ i2c_slave_event(i2c_imx->slave, I2C_SLAVE_READ_REQUESTED, &value);
+
+ /* Slave transmit */
+ ctl |= I2CR_MTX;
+ imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
+
+ /* Send data */
+ imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
+ } else { /* Master wants to write to us */
+ dev_dbg(&i2c_imx->adapter.dev, "write requested");
+ i2c_slave_event(i2c_imx->slave, I2C_SLAVE_WRITE_REQUESTED, &value);
+
+ /* Slave receive */
+ ctl &= ~I2CR_MTX;
+ imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
+ /* Dummy read */
+ imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+ }
+ } else if (!(ctl & I2CR_MTX)) { /* Receive mode */
+ if (status & I2SR_IBB) { /* No STOP signal detected */
+ value = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+ i2c_slave_event(i2c_imx->slave, I2C_SLAVE_WRITE_RECEIVED, &value);
+ } else { /* STOP signal is detected */
+ dev_dbg(&i2c_imx->adapter.dev,
+ "STOP signal detected");
+ i2c_slave_event(i2c_imx->slave, I2C_SLAVE_STOP, &value);
+ }
+ } else if (!(status & I2SR_RXAK)) { /* Transmit mode received ACK */
+ ctl |= I2CR_MTX;
+ imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
+
+ i2c_slave_event(i2c_imx->slave, I2C_SLAVE_READ_PROCESSED, &value);
+
+ imx_i2c_write_reg(value, i2c_imx, IMX_I2C_I2DR);
+ } else { /* Transmit mode received NAK */
+ ctl &= ~I2CR_MTX;
+ imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
+ imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static irqreturn_t i2c_imx_master_isr(struct imx_i2c_struct *i2c_imx, unsigned int status)
+{
+ /* Save status register */
+ i2c_imx->i2csr = status | I2SR_IIF;
+ wake_up(&i2c_imx->queue);
+
+ return IRQ_HANDLED;
+}
+
static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
{
struct imx_i2c_struct *i2c_imx = dev_id;
- unsigned int temp;
+ unsigned int ctl, status;
+
+ status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
+ ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+
+ if (status & I2SR_IIF) {
+ i2c_imx_clr_if_bit(status, i2c_imx);
+ if (IS_ENABLED(CONFIG_I2C_SLAVE) && i2c_imx->slave && !(ctl & I2CR_MSTA))
+ return i2c_imx_slave_isr(i2c_imx, status, ctl);

- temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
- if (temp & I2SR_IIF) {
- /* save status register */
- i2c_imx->i2csr = temp;
- temp &= ~I2SR_IIF;
- temp |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IIF);
- imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
- wake_up(&i2c_imx->queue);
- return IRQ_HANDLED;
+ return i2c_imx_master_isr(i2c_imx, status);
}

return IRQ_NONE;
@@ -918,6 +1020,38 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
return 0;
}

+static int i2c_imx_slave_init(struct imx_i2c_struct *i2c_imx)
+{
+ int temp;
+
+ /* Resume */
+ temp = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
+ if (temp < 0) {
+ dev_err(&i2c_imx->adapter.dev, "failed to resume i2c controller");
+ return temp;
+ }
+
+ /* Set slave addr. */
+ imx_i2c_write_reg((i2c_imx->slave->addr << 1), i2c_imx, IMX_I2C_IADR);
+
+ i2c_imx_reset_regs(i2c_imx);
+
+ /* Enable module */
+ temp = i2c_imx->hwdata->i2cr_ien_opcode;
+ imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+ /* Enable interrupt from i2c module */
+ temp |= I2CR_IIEN;
+ imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+ i2c_imx_enable_bus_idle(i2c_imx);
+
+ /* Wait controller to be stable */
+ usleep_range(50, 150);
+
+ return 0;
+}
+
static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
struct i2c_msg *msgs, int num, bool atomic)
{
@@ -999,6 +1133,12 @@ static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
dev_dbg(&i2c_imx->adapter.dev, "<%s> exit with: %s: %d\n", __func__,
(result < 0) ? "error" : "success msg",
(result < 0) ? result : num);
+ /* After data is transferred, switch to slave mode(as a receiver) */
+ if (IS_ENABLED(CONFIG_I2C_SLAVE) && i2c_imx->slave) {
+ if (i2c_imx_slave_init(i2c_imx) < 0)
+ dev_err(&i2c_imx->adapter.dev, "failed to switch to slave mode");
+ }
+
return (result < 0) ? result : num;
}

@@ -1108,10 +1248,58 @@ static u32 i2c_imx_func(struct i2c_adapter *adapter)
| I2C_FUNC_SMBUS_READ_BLOCK_DATA;
}

+static int i2c_imx_reg_slave(struct i2c_client *client)
+{
+ struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(client->adapter);
+ int ret;
+
+ if (!IS_ENABLED(CONFIG_I2C_SLAVE))
+ return -EINVAL;
+
+ if (i2c_imx->slave)
+ return -EBUSY;
+
+ i2c_imx->slave = client;
+
+ ret = i2c_imx_slave_init(i2c_imx);
+ if (ret < 0)
+ dev_err(&i2c_imx->adapter.dev, "failed to switch to slave mode");
+
+ return ret;
+}
+
+static int i2c_imx_unreg_slave(struct i2c_client *client)
+{
+ struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(client->adapter);
+ int ret;
+
+ if (!IS_ENABLED(CONFIG_I2C_SLAVE))
+ return -EINVAL;
+
+ if (!i2c_imx->slave)
+ return -EINVAL;
+
+ /* Reset slave address. */
+ imx_i2c_write_reg(0, i2c_imx, IMX_I2C_IADR);
+
+ i2c_imx_reset_regs(i2c_imx);
+
+ i2c_imx->slave = NULL;
+
+ /* Suspend */
+ ret = pm_runtime_put_sync(i2c_imx->adapter.dev.parent);
+ if (ret < 0)
+ dev_err(&i2c_imx->adapter.dev, "failed to suspend i2c controller");
+
+ return ret;
+}
+
static const struct i2c_algorithm i2c_imx_algo = {
.master_xfer = i2c_imx_xfer,
.master_xfer_atomic = i2c_imx_xfer_atomic,
.functionality = i2c_imx_func,
+ .reg_slave = i2c_imx_reg_slave,
+ .unreg_slave = i2c_imx_unreg_slave,
};

static int i2c_imx_probe(struct platform_device *pdev)
@@ -1207,10 +1395,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
clk_notifier_register(i2c_imx->clk, &i2c_imx->clk_change_nb);
i2c_imx_set_clk(i2c_imx, clk_get_rate(i2c_imx->clk));

- /* Set up chip registers to defaults */
- imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode ^ I2CR_IEN,
- i2c_imx, IMX_I2C_I2CR);
- imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
+ i2c_imx_reset_regs(i2c_imx);

/* Init optional bus recovery function */
ret = i2c_imx_init_recovery_info(i2c_imx, pdev);
--
2.17.1

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