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SubjectRe: [v5] i2c: imx: support slave mode for imx I2C driver
Hi,

Some more comments inline.

On Fri, Nov 29, 2019 at 05:05:13PM +0800, Biwen Li wrote:
> The patch supports slave mode for imx I2C driver
>
> Signed-off-by: Biwen Li <biwen.li@nxp.com>
> ---
> 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 | 216 ++++++++++++++++++++++++++++++++---
> 1 file changed, 198 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index a3b61336fe55..52f70de16900 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -203,6 +203,9 @@ struct imx_i2c_struct {
> struct pinctrl_state *pinctrl_pins_gpio;
>
> struct imx_i2c_dma *dma;
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> + struct i2c_client *slave;
> +#endif
> };
>
> static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
> @@ -279,6 +282,14 @@ 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)
> @@ -588,23 +599,33 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)
> imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
> }
>
> -static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
> +/* Clear interrupt flag bit */
> +static void i2c_imx_clr_if_bit(unsigned int status, struct imx_i2c_struct *i2c_imx)
> {
> - struct imx_i2c_struct *i2c_imx = dev_id;
> - unsigned int temp;
> + status &= ~I2SR_IIF;
> + status |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IIF);
> + imx_i2c_write_reg(status, i2c_imx, IMX_I2C_I2SR);
> +}
>
> - 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;
> - }
> +/* Clear arbitration lost bit */
> +static void i2c_imx_clr_al_bit(unsigned int status, struct imx_i2c_struct *i2c_imx)
> +{

Can you please remove some of the really obvious comments? When a
function is named clr_al_bit, then it doesn't need a comment which says
that this function really does this. There are more comments like this
in the patch.

> + status &= ~I2SR_IAL;
> + status |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IAL);
> + imx_i2c_write_reg(status, i2c_imx, IMX_I2C_I2SR);
> +}
>
> - return IRQ_NONE;
> +static irqreturn_t i2c_imx_master_isr(struct imx_i2c_struct *i2c_imx)
> +{
> + unsigned int status;
> +
> + /* Save status register */
> + status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> + i2c_imx->i2csr = status | I2SR_IIF;

Instead of reading the status register again you could set
i2c_imx->i2csr in the caller.

> +
> + wake_up(&i2c_imx->queue);
> +
> + return IRQ_HANDLED;
> }
>
> static int i2c_imx_dma_write(struct imx_i2c_struct *i2c_imx,
> @@ -900,6 +921,13 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>
> dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
>
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> + if (i2c_imx->slave) {
> + dev_err(&i2c_imx->adapter.dev, "Please not do operations of master mode in slave mode");
> + return -EBUSY;
> + }
> +#endif
> +
> result = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
> if (result < 0)
> goto out;
> @@ -1048,11 +1076,166 @@ static u32 i2c_imx_func(struct i2c_adapter *adapter)
> | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
> }
>
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +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);

Do these have to be two register accesses?

> +
> + /* Wait controller to be stable */
> + usleep_range(50, 150);
> + return 0;
> +}
> +
> +static irqreturn_t i2c_imx_slave_isr(struct imx_i2c_struct *i2c_imx)
> +{
> + unsigned int status, ctl;
> + u8 value;
> +
> + if (!i2c_imx->slave) {
> + dev_err(&i2c_imx->adapter.dev, "cannot deal with slave irq,i2c_imx->slave is null");
> + return IRQ_NONE;
> + }

This function is never called with !i2c_imx->slave.

> +
> + status = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
> + ctl = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
> + if (status & I2SR_IAL) { /* Arbitration lost */
> + i2c_imx_clr_al_bit(status, 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 */
> + ctl &= ~I2CR_MTX;
> + imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
> +
> + 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 int i2c_imx_reg_slave(struct i2c_client *client)
> +{
> + struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(client->adapter);
> + int ret;
> + 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");

The caller already reports an error. No need to do it here again.

> +
> + 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 (!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");

I doubt this message is useful.

Sascha

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