Subject: Re: [PATCH net-next v7 2/9] i2c: designware: Add driver support for Wangxun 10Gb NIC

From: Piotr Raczynski <[email-masked]>
Date: Tue, 9 May 2023 15:52:23 +0200

On Tue, May 09, 2023 at 10:27:27AM +0800, Jiawen Wu wrote:
> Wangxun 10Gb ethernet chip is connected to Designware I2C, to communicate
> with SFP.
> 
> Introduce the property "snps,i2c-platform" to match device data for Wangxun
> in software node case. Since IO resource was mapped on the ethernet driver,
> add a model quirk to get regmap from parent device.
> 
> The exists IP limitations are dealt as workarounds:
> - IP does not support interrupt mode, it works on polling mode.
> - Additionally set FIFO depth address the chip issue.
> 
> Signed-off-by: Jiawen Wu <[email-masked]>

I'm definitely not an i2c expert, a couple of nit picks below, thanks.
Reviewed-by: Piotr Raczynski <[email-masked]>

> ---
>  drivers/i2c/busses/i2c-designware-common.c  |  8 ++
>  drivers/i2c/busses/i2c-designware-core.h    |  1 +
>  drivers/i2c/busses/i2c-designware-master.c  | 89 +++++++++++++++++++--
>  drivers/i2c/busses/i2c-designware-platdrv.c | 15 ++++
>  4 files changed, 108 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
> index 0dc6b1ce663f..a7c2e67ccbf6 100644
> --- a/drivers/i2c/busses/i2c-designware-common.c
> +++ b/drivers/i2c/busses/i2c-designware-common.c
> @@ -575,6 +575,14 @@ int i2c_dw_set_fifo_size(struct dw_i2c_dev *dev)
>  	unsigned int param;
>  	int ret;
>  
> +	/* DW_IC_COMP_PARAM_1 not implement for IP issue */
> +	if ((dev->flags & MODEL_MASK) == MODEL_WANGXUN_SP) {
> +		dev->tx_fifo_depth = 4;
I understand this is some kind of workaround but is the number chosen
empirically? Maybe a defined value would be clearer instead of magic
number.
> +		dev->rx_fifo_depth = 0;
> +
> +		return 0;
> +	}
> +
>  	/*
>  	 * Try to detect the FIFO depth if not set by interface driver,
>  	 * the depth could be from 2 to 256 from HW spec.
> diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
> index c5d87aae39c6..e2213b08d724 100644
> --- a/drivers/i2c/busses/i2c-designware-core.h
> +++ b/drivers/i2c/busses/i2c-designware-core.h
> @@ -303,6 +303,7 @@ struct dw_i2c_dev {
>  #define MODEL_MSCC_OCELOT			BIT(8)
>  #define MODEL_BAIKAL_BT1			BIT(9)
>  #define MODEL_AMD_NAVI_GPU			BIT(10)
> +#define MODEL_WANGXUN_SP			BIT(11)
>  #define MODEL_MASK				GENMASK(11, 8)
>  
>  /*
> diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
> index 55ea91a63382..3bfd7a2232db 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -354,6 +354,68 @@ static int amd_i2c_dw_xfer_quirk(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  	return 0;
>  }
>  
> +static int i2c_dw_poll_tx_empty(struct dw_i2c_dev *dev)
> +{
> +	u32 val;
> +
> +	return regmap_read_poll_timeout(dev->map, DW_IC_RAW_INTR_STAT, val,
> +					val & DW_IC_INTR_TX_EMPTY,
> +					100, 1000);
> +}
> +
> +static int i2c_dw_poll_rx_full(struct dw_i2c_dev *dev)
> +{
> +	u32 val;
> +
> +	return regmap_read_poll_timeout(dev->map, DW_IC_RAW_INTR_STAT, val,
> +					val & DW_IC_INTR_RX_FULL,
> +					100, 1000);
> +}
> +
> +static int txgbe_i2c_dw_xfer_quirk(struct i2c_adapter *adap, struct i2c_msg *msgs,
> +				   int num_msgs)
> +{
> +	struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
> +	int msg_idx, buf_len, data_idx, ret;
> +	unsigned int val, stop = 0;
> +	u8 *buf;
> +
> +	dev->msgs = msgs;
> +	dev->msgs_num = num_msgs;
> +	i2c_dw_xfer_init(dev);
> +	regmap_write(dev->map, DW_IC_INTR_MASK, 0);
> +
> +	for (msg_idx = 0; msg_idx < num_msgs; msg_idx++) {
> +		buf = msgs[msg_idx].buf;
> +		buf_len = msgs[msg_idx].len;
> +
> +		for (data_idx = 0; data_idx < buf_len; data_idx++) {
> +			if (msg_idx == num_msgs - 1 && data_idx == buf_len - 1)
> +				stop |= BIT(9);
> +
> +			if (msgs[msg_idx].flags & I2C_M_RD) {
> +				regmap_write(dev->map, DW_IC_DATA_CMD, 0x100 | stop);
> +
> +				ret = i2c_dw_poll_rx_full(dev);
> +				if (ret)
> +					return ret;
> +
> +				regmap_read(dev->map, DW_IC_DATA_CMD, &val);
> +				buf[data_idx] = val;
> +			} else {
> +				ret = i2c_dw_poll_tx_empty(dev);
> +				if (ret)
> +					return ret;
> +
> +				regmap_write(dev->map, DW_IC_DATA_CMD,
> +					     buf[data_idx] | stop);
> +			}
> +		}
> +	}
> +
> +	return num_msgs;
> +}
> +
>  /*
>   * Initiate (and continue) low level master read/write transaction.
>   * This function is only called from i2c_dw_isr, and pumping i2c_msg
> @@ -559,13 +621,19 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  	pm_runtime_get_sync(dev->dev);
>  
>  	/*
> -	 * Initiate I2C message transfer when AMD NAVI GPU card is enabled,
> +	 * Initiate I2C message transfer when polling mode is enabled,
>  	 * As it is polling based transfer mechanism, which does not support
>  	 * interrupt based functionalities of existing DesignWare driver.
>  	 */
> -	if ((dev->flags & MODEL_MASK) == MODEL_AMD_NAVI_GPU) {
> +	switch (dev->flags & MODEL_MASK) {
> +	case MODEL_AMD_NAVI_GPU:
>  		ret = amd_i2c_dw_xfer_quirk(adap, msgs, num);
>  		goto done_nolock;
> +	case MODEL_WANGXUN_SP:
> +		ret = txgbe_i2c_dw_xfer_quirk(adap, msgs, num);
> +		goto done_nolock;
> +	default:
> +		break;
>  	}
Nit pick, when I first saw above code it looked a little weird, maybe it would be a
little clearer with:

	if (i2c_dw_is_model_poll(dev)) {
		switch (dev->flags & MODEL_MASK) {
		case MODEL_AMD_NAVI_GPU:
			ret = amd_i2c_dw_xfer_quirk(adap, msgs, num);
			break;
		case MODEL_WANGXUN_SP:
			ret = txgbe_i2c_dw_xfer_quirk(adap, msgs, num);
			break;
		default:
			break;
		}
		goto done_nolock;
	}

I do not insist though.

>  
>  	reinit_completion(&dev->cmd_complete);
> @@ -848,7 +916,7 @@ static int i2c_dw_init_recovery_info(struct dw_i2c_dev *dev)
>  	return 0;
>  }
>  
> -static int amd_i2c_adap_quirk(struct dw_i2c_dev *dev)
> +static int i2c_dw_poll_adap_quirk(struct dw_i2c_dev *dev)
>  {
>  	struct i2c_adapter *adap = &dev->adapter;
>  	int ret;
> @@ -862,6 +930,17 @@ static int amd_i2c_adap_quirk(struct dw_i2c_dev *dev)
>  	return ret;
>  }
>  
> +static bool i2c_dw_is_model_poll(struct dw_i2c_dev *dev)
> +{
> +	switch (dev->flags & MODEL_MASK) {
> +	case MODEL_AMD_NAVI_GPU:
> +	case MODEL_WANGXUN_SP:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
>  int i2c_dw_probe_master(struct dw_i2c_dev *dev)
>  {
>  	struct i2c_adapter *adap = &dev->adapter;
> @@ -917,8 +996,8 @@ int i2c_dw_probe_master(struct dw_i2c_dev *dev)
>  	adap->dev.parent = dev->dev;
>  	i2c_set_adapdata(adap, dev);
>  
> -	if ((dev->flags & MODEL_MASK) == MODEL_AMD_NAVI_GPU)
> -		return amd_i2c_adap_quirk(dev);
> +	if (i2c_dw_is_model_poll(dev))
> +		return i2c_dw_poll_adap_quirk(dev);
>  
>  	if (dev->flags & ACCESS_NO_IRQ_SUSPEND) {
>  		irq_flags = IRQF_NO_SUSPEND;
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 89ad88c54754..1bf50150386d 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -168,6 +168,15 @@ static inline int dw_i2c_of_configure(struct platform_device *pdev)
>  }
>  #endif
>  
> +static int txgbe_i2c_request_regs(struct dw_i2c_dev *dev)
> +{
> +	dev->map = dev_get_regmap(dev->dev->parent, NULL);
> +	if (!dev->map)
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +
>  static void dw_i2c_plat_pm_cleanup(struct dw_i2c_dev *dev)
>  {
>  	pm_runtime_disable(dev->dev);
> @@ -185,6 +194,9 @@ static int dw_i2c_plat_request_regs(struct dw_i2c_dev *dev)
>  	case MODEL_BAIKAL_BT1:
>  		ret = bt1_i2c_request_regs(dev);
>  		break;
> +	case MODEL_WANGXUN_SP:
> +		ret = txgbe_i2c_request_regs(dev);
> +		break;
>  	default:
>  		dev->base = devm_platform_ioremap_resource(pdev, 0);
>  		ret = PTR_ERR_OR_ZERO(dev->base);
> @@ -277,6 +289,9 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	dev->flags = (uintptr_t)device_get_match_data(&pdev->dev);
> +	if (device_property_present(&pdev->dev, "snps,i2c-platform"))
> +		dev->flags |= MODEL_WANGXUN_SP;
> +
>  	dev->dev = &pdev->dev;
>  	dev->irq = irq;
>  	platform_set_drvdata(pdev, dev);
> -- 
> 2.27.0
> 
>