Subject: [PATCH 1/3] i2c: tegra: implement slave mode

From: [email-masked] (Marc Dietrich)
Date: Thu, 29 Jan 2015 10:40:29 +0100

Hi Andrey,

first, thanks for accepting the challenge once more ;-)

The driver depends on I2C_SLAVE now, so you need to add this to Kconfig. The 
amount of code (and additional overhead) is pretty small, so I think it's ok 
to always enable it. Otherwise we would need lots of ifdefs.

Am Donnerstag, 29. Januar 2015, 10:20:20 schrieb Andrey Danin:
> Initialization code is based on NVEC driver.
> 
> There is a HW bug in AP20 that was also mentioned in kernel sources
> for Toshiba AC100.
> 
> Signed-off-by: Andrey Danin <[email-masked]>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 131
> +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 131 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 28b87e6..cfc4e67 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -42,8 +42,15 @@
>  #define I2C_SL_CNFG				0x020
>  #define I2C_SL_CNFG_NACK			(1<<1)
>  #define I2C_SL_CNFG_NEWSL			(1<<2)
> +#define I2C_SL_RCVD				0x024
> +#define I2C_SL_STATUS				0x028
> +#define I2C_SL_ST_IRQ				(1<<3)
> +#define I2C_SL_ST_END_TRANS			(1<<4)
> +#define I2C_SL_ST_RCVD				(1<<2)
> +#define I2C_SL_ST_RNW				(1<<1)
>  #define I2C_SL_ADDR1				0x02c
>  #define I2C_SL_ADDR2				0x030
> +#define I2C_SL_DELAY_COUNT			0x03c
>  #define I2C_TX_FIFO				0x050
>  #define I2C_RX_FIFO				0x054
>  #define I2C_PACKET_TRANSFER_STATUS		0x058
> @@ -125,6 +132,8 @@ enum msg_end_type {
>   * @clk_divisor_std_fast_mode: Clock divisor in standard/fast mode. It is
>   *		applicable if there is no fast clock source i.e. single clock
>   *		source.
> + * @slave_read_start_delay: Workaround for AP20 I2C Slave Controller bug.
> Delay + *              before writing data byte into register I2C_SL_RCVD.
> */
> 
>  struct tegra_i2c_hw_feature {
> @@ -133,6 +142,7 @@ struct tegra_i2c_hw_feature {
>  	bool has_single_clk_source;
>  	int clk_divisor_hs_mode;
>  	int clk_divisor_std_fast_mode;
> +	int slave_read_start_delay;
>  };
> 
>  /**
> @@ -173,6 +183,7 @@ struct tegra_i2c_dev {
>  	int msg_read;
>  	u32 bus_clk_rate;
>  	bool is_suspended;
> +	struct i2c_client *slave;
>  };
> 
>  static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val, unsigned
> long reg) @@ -398,6 +409,12 @@ static inline int
> tegra_i2c_clock_enable(struct tegra_i2c_dev *i2c_dev)
> 
>  static inline void tegra_i2c_clock_disable(struct tegra_i2c_dev *i2c_dev)
>  {
> +	if (i2c_dev->slave) {
> +		dev_warn(i2c_dev->dev,
> +			"i2c slave is registered, don't disable a clock\n");
> +		return;
> +	}
> +

is this really required? What are the callers of clock_disable? I think it 
would be ok to make master or slave operation exclusive for now. We have no 
way to test this anyway. Maybe some flag which blocks master operation.

>  	clk_disable(i2c_dev->div_clk);
>  	if (!i2c_dev->hw->has_single_clk_source)
>  		clk_disable(i2c_dev->fast_clk);
> @@ -459,12 +476,84 @@ static int tegra_i2c_init(struct tegra_i2c_dev
> *i2c_dev) return err;
>  }
> 
> +static inline int is_ready(unsigned long status)
> +{
> +	return status & I2C_SL_ST_IRQ;
> +}

is_slave_irq?

> +
> +static inline int is_write(unsigned long status)
> +{
> +	return (status & I2C_SL_ST_RNW) == 0;
> +}
> +
> +static inline int is_read(unsigned long status)
> +{
> +	return !is_write(status);
> +}
> +
> +static inline int is_trans_start(unsigned long status)
> +{
> +	return status & I2C_SL_ST_RCVD;
> +}
> +
> +static inline int is_trans_end(unsigned long status)
> +{
> +	return status & I2C_SL_ST_END_TRANS;
> +}

Following the rest of the files coding style, I think this helpers can be 
moved to the caller itself. 

> +
> +static bool tegra_i2c_slave_isr(int irq, struct tegra_i2c_dev *i2c_dev)
> +{
> +	unsigned long status;
> +	u8 value;
> +
> +	if (!i2c_dev->slave || !i2c_dev->slave->slave_cb)
> +		return false;
> +
> +	status = i2c_readl(i2c_dev, I2C_SL_STATUS);
> +	if (!is_ready(status))
> +		return false;
> +
> +	/* master sent stop */
> +	if (is_trans_end(status)) {
> +		i2c_slave_event(i2c_dev->slave, I2C_SLAVE_STOP, NULL);
> +		if (!is_trans_start(status))
> +			return true;
> +	}
> +
> +	/* i2c master sends data to us */
> +	if (is_write(status)) {
> +		i2c_slave_event(i2c_dev->slave, I2C_SLAVE_REQ_WRITE_START,
> +				NULL);
> +		value = i2c_readl(i2c_dev, I2C_SL_RCVD);
> +		if (is_trans_start(status))
> +			i2c_writel(i2c_dev, 0, I2C_SL_RCVD);
> +		i2c_slave_event(i2c_dev->slave, I2C_SLAVE_REQ_WRITE_END,
> +				&value);
> +	}
> +
> +	/* i2c master reads data from us */
> +	if (is_read(status)) {
> +		i2c_slave_event(i2c_dev->slave, I2C_SLAVE_REQ_READ_START,
> +				&value);
> +		if (is_trans_start(status)
> +				&& i2c_dev->hw->slave_read_start_delay)
> +			udelay(i2c_dev->hw->slave_read_start_delay);
> +		i2c_writel(i2c_dev, value, I2C_SL_RCVD);
> +		i2c_slave_event(i2c_dev->slave, I2C_SLAVE_REQ_READ_END, NULL);
> +	}
> +
> +	return true;
> +}
> +
>  static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>  {
>  	u32 status;
>  	const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
>  	struct tegra_i2c_dev *i2c_dev = dev_id;
> 
> +	if (tegra_i2c_slave_isr(irq, i2c_dev))
> +		return IRQ_HANDLED;
> +
>  	status = i2c_readl(i2c_dev, I2C_INT_STATUS);
> 
>  	if (status == 0) {
> @@ -660,9 +749,48 @@ static u32 tegra_i2c_func(struct i2c_adapter *adap)
>  	return ret;
>  }
> 
> +static int tegra_reg_slave(struct i2c_client *slave)
> +{
> +	struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(slave->adapter);
> +
> +	if (i2c_dev->slave)
> +		return -EBUSY;
> +
> +	i2c_dev->slave = slave;
> +
> +	tegra_i2c_clock_enable(i2c_dev);
> +
> +	reset_control_assert(i2c_dev->rst);
> +	udelay(2);
> +	reset_control_deassert(i2c_dev->rst);
> +
> +	i2c_writel(i2c_dev, I2C_SL_CNFG_NEWSL, I2C_SL_CNFG);
> +	i2c_writel(i2c_dev, 0x1E, I2C_SL_DELAY_COUNT);
> +
> +	i2c_writel(i2c_dev, slave->addr, I2C_SL_ADDR1);
> +	i2c_writel(i2c_dev, 0, I2C_SL_ADDR2);
> +
> +	return 0;
> +}
> +
> +static int tegra_unreg_slave(struct i2c_client *slave)
> +{
> +	struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(slave->adapter);
> +
> +	WARN_ON(!i2c_dev->slave);
> +
> +	i2c_writel(i2c_dev, 0, I2C_SL_CNFG);
> +
> +	i2c_dev->slave = NULL;
> +
> +	return 0;
> +}
> +
>  static const struct i2c_algorithm tegra_i2c_algo = {
>  	.master_xfer	= tegra_i2c_xfer,
>  	.functionality	= tegra_i2c_func,
> +	.reg_slave		= tegra_reg_slave,
> +	.unreg_slave	= tegra_unreg_slave,
>  };
> 
>  static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
> @@ -671,6 +799,7 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw
> = { .has_single_clk_source = false,
>  	.clk_divisor_hs_mode = 3,
>  	.clk_divisor_std_fast_mode = 0,
> +	.slave_read_start_delay = 8,
>  };
> 
>  static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
> @@ -679,6 +808,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw
> = { .has_single_clk_source = false,
>  	.clk_divisor_hs_mode = 3,
>  	.clk_divisor_std_fast_mode = 0,
> +	.slave_read_start_delay = 0,
>  };
> 
>  static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
> @@ -687,6 +817,7 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw
> = { .has_single_clk_source = true,
>  	.clk_divisor_hs_mode = 1,
>  	.clk_divisor_std_fast_mode = 0x19,
> +	.slave_read_start_delay = 0,
>  };
> 
>  /* Match table for of_platform binding */
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