[PATCH] i2c: mediatek: Add to support continuous mode

[Qii Wang]

Hi Qiangming:
	Do you have the specific timing cost data about the "continuous mode"?
Is it better than the default multi-write mode(one message by one
message) ?I need to know if this patch is very necessary.

On Fri, 2020-06-19 at 16:06 +0800, Qiangming Xia wrote:
> From: "qiangming.xia" <qiangming.xia at mediatek.com>
> 
>     Mediatek i2c controller support for continuous mode,
> it allow to transfer once multiple writing messages of equal length.
>     For example, a slave need write a serial of non-continuous
> offset range in chip,e.g. writing offset 0,offset 2 and offset 4.
> Normally, it need three times i2c write operation. However,it can
> use once transfer to finish it by using continuous mode.
> 
> Change-Id: If06991e3fd32867bdeaacf15bb24864d5c5904d0
> Signed-off-by: Qiangming Xia <qiangming.xia at mediatek.com>
> ---
>  drivers/i2c/busses/i2c-mt65xx.c | 67 +++++++++++++++++++++++++++++++++
>  1 file changed, 67 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index deef69e56906..76ec65d869f6 100644
> --- a/drivers/i2c/busses/i2c-mt65xx.c
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -97,6 +97,7 @@ enum mtk_trans_op {
>  	I2C_MASTER_WR = 1,
>  	I2C_MASTER_RD,
>  	I2C_MASTER_WRRD,
> +	I2C_MASTER_CONTINUOUS_WR,
>  };
>  
>  enum I2C_REGS_OFFSET {
> @@ -846,6 +847,9 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
>  					    OFFSET_TRANSFER_LEN);
>  		}
>  		mtk_i2c_writew(i2c, I2C_WRRD_TRANAC_VALUE, OFFSET_TRANSAC_LEN);
> +	} else if (i2c->op == I2C_MASTER_CONTINUOUS_WR) {
> +		mtk_i2c_writew(i2c, msgs->len / num, OFFSET_TRANSFER_LEN);
> +		mtk_i2c_writew(i2c, num, OFFSET_TRANSAC_LEN);
>  	} else {
>  		mtk_i2c_writew(i2c, msgs->len, OFFSET_TRANSFER_LEN);
>  		mtk_i2c_writew(i2c, num, OFFSET_TRANSAC_LEN);
> @@ -896,6 +900,23 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
>  			writel(reg_4g_mode, i2c->pdmabase + OFFSET_TX_4G_MODE);
>  		}
>  
> +		writel((u32)wpaddr, i2c->pdmabase + OFFSET_TX_MEM_ADDR);
> +		writel(msgs->len, i2c->pdmabase + OFFSET_TX_LEN);
> +	} else if (i2c->op == I2C_MASTER_CONTINUOUS_WR) {
> +		writel(I2C_DMA_INT_FLAG_NONE, i2c->pdmabase + OFFSET_INT_FLAG);
> +		writel(I2C_DMA_CON_TX, i2c->pdmabase + OFFSET_CON);
> +		wpaddr = dma_map_single(i2c->dev, msgs->buf,
> +					msgs->len, DMA_TO_DEVICE);
> +		if (dma_mapping_error(i2c->dev, wpaddr)) {
> +			kfree(msgs->buf);
> +			return -ENOMEM;
> +		}
> +
> +		if (i2c->dev_comp->support_33bits) {
> +			reg_4g_mode = mtk_i2c_set_4g_mode(wpaddr);
> +			writel(reg_4g_mode, i2c->pdmabase + OFFSET_TX_4G_MODE);
> +		}
> +
>  		writel((u32)wpaddr, i2c->pdmabase + OFFSET_TX_MEM_ADDR);
>  		writel(msgs->len, i2c->pdmabase + OFFSET_TX_LEN);
>  	} else {
> @@ -979,6 +1000,11 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
>  				 msgs->len, DMA_FROM_DEVICE);
>  
>  		i2c_put_dma_safe_msg_buf(dma_rd_buf, msgs, true);
> +	} else if (i2c->op == I2C_MASTER_CONTINUOUS_WR) {
> +		dma_unmap_single(i2c->dev, wpaddr,
> +				 msgs->len, DMA_TO_DEVICE);
> +
> +		kfree(msgs->buf);
>  	} else {
>  		dma_unmap_single(i2c->dev, wpaddr, msgs->len,
>  				 DMA_TO_DEVICE);
> @@ -1009,6 +1035,9 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
>  {
>  	int ret;
>  	int left_num = num;
> +	int i, j;
> +	u8 *dma_multi_wr_buf;
> +	struct i2c_msg multi_msg[1];
>  	struct mtk_i2c *i2c = i2c_get_adapdata(adap);
>  
>  	ret = mtk_i2c_clock_enable(i2c);
> @@ -1025,6 +1054,44 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
>  		}
>  	}
>  
> +	if (num > 1) {
> +		for (i = 0; i < num - 1; i++) {
> +			if (!(msgs[i].flags & I2C_M_RD) && !(msgs[i+1].flags &
> +				I2C_M_RD) && (msgs[i].addr == msgs[i+1].addr)
> +					&& (msgs[i].len == msgs[i+1].len)) {
> +				continue;
> +			} else
> +				break;
> +		}
> +		if (i >= num - 1) {
> +			i2c->op = I2C_MASTER_CONTINUOUS_WR;
> +			j = 0;
> +			dma_multi_wr_buf = kzalloc(msgs->len * num, GFP_KERNEL);
> +			if (!dma_multi_wr_buf) {
> +				ret =  -ENOMEM;
> +				goto err_exit;
> +			}
> +			multi_msg->addr  = msgs->addr;
> +			multi_msg->len   = msgs->len * num;
> +			multi_msg->buf   = dma_multi_wr_buf;
> +			multi_msg->flags  = 0;
> +			while (j < num) {
> +				memcpy(dma_multi_wr_buf + msgs->len * j,
> +							msgs->buf, msgs->len);
> +				j++;
> +				msgs++;
> +				}
> +
> +			i2c->ignore_restart_irq = false;
> +			ret = mtk_i2c_do_transfer(i2c, multi_msg, num, 0);
> +			if (ret < 0)
> +				goto err_exit;
> +			ret = num;
> +				goto err_exit;
> +
> +		}
> +	}
> +
>  	if (i2c->auto_restart && num >= 2 && i2c->speed_hz > I2C_MAX_FAST_MODE_FREQ)
>  		/* ignore the first restart irq after the master code,
>  		 * otherwise the first transfer will be discarded.