linux-kernel - Re: [RESEND PATCH 1/4] i2c: i2c-bcm-kona: Introduce Broadcom I2C Driver

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Message-ID: <20131101124958.GB6734@katana>
Date:	Fri, 1 Nov 2013 13:49:58 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Tim Kryger <tim.kryger@...aro.org>
Cc:	Christian Daudt <bcm@...thebug.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH 1/4] i2c: i2c-bcm-kona: Introduce Broadcom I2C
 Driver

On Wed, Oct 16, 2013 at 03:01:46PM -0700, Tim Kryger wrote:
> Introduce support for Broadcom Serial Controller (BSC) I2C bus found
> in the Kona family of Mobile SoCs.  FIFO hardware is utilized but only
> standard mode (100kHz), fast mode (400kHz), and fast mode plus (1MHz)
> bus speeds are supported.
> 
> Signed-off-by: Tim Kryger <tim.kryger@...aro.org>
> Reviewed-by: Matt Porter <matt.porter@...aro.org>
> Reviewed-by: Markus Mayer <markus.mayer@...aro.org>

Looks mostly good, some remarks:

> +struct bcm_kona_i2c_dev {
> +	/* Pointer to linux device struct */
> +	struct device *device;
> +
> +	/* Virtual address where registers are mapped */
> +	void __iomem *base;
> +
> +	/* Interrupt */
> +	int irq;
> +
> +	/* Standard Speed configuration */
> +	const struct bus_speed_cfg *std_cfg;
> +
> +	/* Linux I2C adapter struct */
> +	struct i2c_adapter adapter;
> +
> +	/* Lock for the I2C device */
> +	struct mutex i2c_bcm_lock;
> +
> +	/* Completion to signal an operation finished */
> +	struct completion done;
> +
> +	/* Handle for external clock */
> +	struct clk *external_clk;
> +};

IMO most of the comments could go. Kind of stating the obvious :)


> +/* Read any amount of data using the RX FIFO from the i2c bus */
> +static int bcm_kona_i2c_read_fifo(struct bcm_kona_i2c_dev *dev,
> +				  struct i2c_msg *msg)
> +{
> +	unsigned int bytes_to_read = MAX_RX_FIFO_SIZE;
> +	unsigned int last_byte_nak = 0;
> +	unsigned int bytes_read = 0;
> +	unsigned int rc;

Should be signed.

> +/* Write any amount of data using TX FIFO to the i2c bus */
> +static int bcm_kona_i2c_write_fifo(struct bcm_kona_i2c_dev *dev,
> +				   struct i2c_msg *msg)
> +{
> +	unsigned int bytes_to_write = MAX_TX_FIFO_SIZE;
> +	unsigned int bytes_written = 0;
> +	unsigned int rc;

Ditto signed.

> +/* Master transfer function */
> +static int bcm_kona_i2c_xfer(struct i2c_adapter *adapter,
> +			     struct i2c_msg msgs[], int num)
> +{
> +	struct bcm_kona_i2c_dev *dev = i2c_get_adapdata(adapter);
> +	struct i2c_msg *pmsg;
> +	int rc = 0;
> +	int i;
> +
> +	mutex_lock(&dev->i2c_bcm_lock);

Huh? Why do you need that? The core has locks per bus.

> +static int bcm_kona_i2c_assign_bus_speed(struct bcm_kona_i2c_dev *dev)
> +{
> +	unsigned int bus_speed;
> +	int ret = of_property_read_u32(dev->device->of_node, "clock-frequency",
> +				       &bus_speed);
> +	if (ret < 0) {
> +		dev_err(dev->device, "missing clock-frequency property\n");
> +		return -ENODEV;
> +	}
> +
> +	switch (bus_speed) {
> +	case 100000:
> +		dev->std_cfg = &std_cfg_table[BCM_SPD_100K];
> +		break;
> +	case 400000:
> +		dev->std_cfg = &std_cfg_table[BCM_SPD_400K];
> +		break;
> +	case 1000000:
> +		dev->std_cfg = &std_cfg_table[BCM_SPD_1MHZ];
> +		break;
> +	default:
> +		pr_err("%d hz bus speed not supported\n", bus_speed);
> +		return -EINVAL;
> +	};

Unneeded semicolon.

> +
> +	return 0;
> +}
> +
> +static int bcm_kona_i2c_probe(struct platform_device *pdev)
> +{
> +	int rc = 0;
> +	struct bcm_kona_i2c_dev *dev;
> +	struct i2c_adapter *adap;
> +	struct resource *iomem;
> +
> +	/* Allocate memory for private data structure */
> +	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
> +	if (!dev) {
> +		rc = -ENOMEM;
> +		goto probe_return;

I'd prefer simply return -Esomething. The printout at probe_return is
also available via driver core.

...

> +	/* Add the i2c adapter */
> +	adap = &dev->adapter;
> +	i2c_set_adapdata(adap, dev);
> +	adap->owner = THIS_MODULE;
> +	adap->class = UINT_MAX;	/* can be used by any I2C device */

Why do you need class based instantiation. It will most likely cost
boot-time and you have devicetree means for doing instantiation.


> +	strlcpy(adap->name, "Broadcom I2C adapter", sizeof(adap->name));
> +	adap->algo = &bcm_algo;
> +	adap->dev.parent = &pdev->dev;
> +	adap->nr = pdev->id;
> +	adap->dev.of_node = pdev->dev.of_node;
> +
> +	rc = i2c_add_numbered_adapter(adap);

Maybe you want simply i2c_add_adapter here since the core has no
built-in support for of aliases?

> +
> +MODULE_AUTHOR("Broadcom");

Some email address please.

> +MODULE_DESCRIPTION("Broadcom Kona I2C Driver");
> +MODULE_LICENSE("GPL v2");

Thanks,

   Wolfram


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