Subject: [PATCH v5 1/3] i2c-mv64xxx: Add I2C Transaction Generator support

From: [email-masked] (Wolfram Sang)
Date: Wed, 21 Aug 2013 23:01:17 +0200

Hi,

here is the review. BTW have you tested with and without the offload
engine?

> +static int mv64xxx_i2c_offload_msg(struct mv64xxx_i2c_data *drv_data)
> +{
> +	unsigned long data_reg_hi = 0;
> +	unsigned long data_reg_lo = 0;
> +	unsigned long ctrl_reg;
> +	unsigned int i;
> +	struct i2c_msg *msg = drv_data->msgs;
> +
> +	drv_data->msg = msg;
> +	drv_data->byte_posn = 0;
> +	drv_data->bytes_left = msg->len;
> +	drv_data->aborting = 0;
> +	drv_data->rc = 0;
> +	/* Only regular transactions can be offloaded */
> +	if ((msg->flags & ~(I2C_M_TEN | I2C_M_RD)) != 0)
> +		return 1;

-EINVAL?

> +
> +	/* Only 1-8 byte transfers can be offloaded */
> +	if (msg->len < 1 || msg->len > 8)
> +		return 1;

ditto

> +
> +	/* Build transaction */
> +	ctrl_reg = MV64XXX_I2C_BRIDGE_CONTROL_ENABLE |
> +		   (msg->addr << MV64XXX_I2C_BRIDGE_CONTROL_ADDR_SHIFT);
> +
> +	if ((msg->flags & I2C_M_TEN) != 0)
> +		ctrl_reg |=  MV64XXX_I2C_BRIDGE_CONTROL_ADDR_EXT;
> +
> +	if ((msg->flags & I2C_M_RD) == 0) {
> +		for (i = 0; i < 4 && i < msg->len; i++)
> +			data_reg_lo = data_reg_lo |
> +					(msg->buf[i] << ((i & 0x3) * 8));
> +
> +		for (i = 4; i < 8 && i < msg->len; i++)
> +			data_reg_hi = data_reg_hi |
> +					(msg->buf[i] << ((i & 0x3) * 8));

What about:

	local_buf[8] = { 0 };

	memcpy(local_buf, msg->buf, msg->len);
	cpu_to_be32(...)

? A lot less lines and be32 macros are likely more efficient. Copy loop
probably, too.

> +
> +		ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_WR |
> +		    (msg->len - 1) << MV64XXX_I2C_BRIDGE_CONTROL_TX_SIZE_SHIFT;
> +	} else {
> +		ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_RD |
> +		    (msg->len - 1) << MV64XXX_I2C_BRIDGE_CONTROL_RX_SIZE_SHIFT;
> +	}
> +
> +	/* Execute transaction */
> +	writel_relaxed(data_reg_lo,
> +		drv_data->reg_base + MV64XXX_I2C_REG_TX_DATA_LO);
> +	writel_relaxed(data_reg_hi,
> +		drv_data->reg_base + MV64XXX_I2C_REG_TX_DATA_HI);

Do you need to write the 0 in case of I2C_M_RD?

> +	writel(ctrl_reg, drv_data->reg_base + MV64XXX_I2C_REG_BRIDGE_CONTROL);
> +
> +	return 0;
> +}
> +
> +static void
> +mv64xxx_i2c_update_offload_data(struct i2c_msg *msg, unsigned long data_reg_hi,
> +	unsigned long data_reg_lo)
> +{
> +	int i;
> +
> +	if ((msg->flags & I2C_M_RD) != 0) {

!= 0 is superfluous

> +		for (i = 0; i < 4 && i < msg->len; i++) {
> +			msg->buf[i] = data_reg_lo & 0xFF;
> +			data_reg_lo >>= 8;
> +		}
> +
> +		for (i = 4; i < 8 && i < msg->len; i++) {
> +			msg->buf[i] = data_reg_hi & 0xFF;
> +			data_reg_hi >>= 8;
> +		}
> +	}

Same idea as above?

> @@ -298,21 +420,36 @@ mv64xxx_i2c_fsm(struct mv64xxx_i2c_data *drv_data, u32 status)
>  static void
>  mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
>  {
> +	unsigned long data_reg_hi = 0;
> +	unsigned long data_reg_lo = 0;
> +
>  	switch(drv_data->action) {
> +	case MV64XXX_I2C_ACTION_OFFLOAD_RESTART:
> +		data_reg_lo = readl(drv_data->reg_base +
> +				MV64XXX_I2C_REG_RX_DATA_LO);
> +		data_reg_hi = readl(drv_data->reg_base +
> +				MV64XXX_I2C_REG_RX_DATA_HI);

Initializing data_reg_* is the same for both calls to
update_offload_data, so it could be moved into the function.
Probably not needed when using the local_buf idea.

> @@ -326,6 +463,12 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
>  			drv_data->reg_base + drv_data->reg_offsets.control);
>  		break;
>  
> +	case MV64XXX_I2C_ACTION_OFFLOAD_SEND_START:
> +		if (mv64xxx_i2c_offload_msg(drv_data) <= 0)

needs to be adjusted when using -EINVAL above. I'd prefer the error case
in the else branch, though. Easier to read.

> +			break;
> +		else
> +			drv_data->action = MV64XXX_I2C_ACTION_SEND_START;
> +		/* FALLTHRU */
>  	case MV64XXX_I2C_ACTION_SEND_START:
>  		writel(drv_data->cntl_bits | MV64XXX_I2C_REG_CONTROL_START,
>  			drv_data->reg_base + drv_data->reg_offsets.control);

> @@ -601,6 +779,13 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
>  
>  	memcpy(&drv_data->reg_offsets, device->data, sizeof(drv_data->reg_offsets));
>  
> +	/*
> +	 * For controllers embedded in new SoCs activate the
> +	 * Transaction Generator support.
> +	 */
> +	if (of_device_is_compatible(np, "marvell,mv78230-i2c"))
> +		drv_data->offload_enabled = true;

For now OK, if there are more users, someone will need to convert it to
be included in match_data.

> @@ -654,6 +839,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
>  		drv_data->freq_n = pdata->freq_n;
>  		drv_data->irq = platform_get_irq(pd, 0);
>  		drv_data->adapter.timeout = msecs_to_jiffies(pdata->timeout);
> +		drv_data->offload_enabled = 0;

'false' instead of 0.

Regards,

   Wolfram

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