Subject: Re: [Linux-zigbee-devel] [PATCH net-next 1/3] ieee802154: cc2520: driver for TI cc2520 radio

From: Varka Bhadram <[email-masked]>
Date: Mon, 16 Jun 2014 14:21:19 +0530

Hi Alex,

Thanks for the comments.

I will create a patch for the required changes with Reported-by 
Alexander Aring  <...> reply if this is okay for you.

On 06/16/2014 01:08 PM, Alexander Aring wrote:
> Hi Varka,
>
> On Mon, Jun 16, 2014 at 10:21:56AM +0530, Varka Bhadram wrote:
> Maybe some more information about this chip in the commit msg?
I will provide the proper commit messages in next version
>
> +/*Generic Functions*/
> +static int cc2520_cmd_strobe(struct cc2520_private *priv,
> +						u8 cmd)
> +{
> +	int ret;
> +	u8 status = 0xff;
> +	struct spi_message msg;
> +	struct spi_transfer xfer = {
> +		.len = 0,
> +		.tx_buf = priv->buf,
> +		.rx_buf = priv->buf,
> +	};
> +
> +	spi_message_init(&msg);
> +	spi_message_add_tail(&xfer, &msg);
> I see, you maybe looked at others drivers like at86rf230 and see what
> they do there. I really don't like the lowlevel spi calls in the others
> drivers. There are spi helper functions like 'spi_write_then_read' look
> in drivers/spi/spi.c for the helper functions. Then you don't need the
> buffer_mutex also.
In at86rf230 driver first it hold the mutex lock for buffer then 
__at86rf230_read_subreg()/ __at86rf230_write()
functions called. One more thing is that at the low level spi core is 
holding the lock for the buffer data.
We can remove the buffer mutex.
>> +
>> +	mutex_lock(&priv->buffer_mutex);
>> +	priv->buf[xfer.len++] = cmd;
>> +	dev_vdbg(&priv->spi->dev,
>> +			"command strobe buf[0] = %02x\n",
>> +			priv->buf[0]);
>> +
>> +	ret = spi_sync(priv->spi, &msg);
>> +	if (!ret)
>> +		status = priv->buf[0];
>> +	dev_vdbg(&priv->spi->dev,
>> +			"buf[0] = %02x\n", priv->buf[0]);
>> +	mutex_unlock(&priv->buffer_mutex);
>> +
>> +	return ret;
>> +}
>> +
> ....
>
>> +
>> +static void cc2520_unregister(struct cc2520_private *priv)
>> +{
>> +	ieee802154_unregister_device(priv->dev);
>> +	ieee802154_free_device(priv->dev);
>> +}
> Only used in remove callback of module. It's small enough to do this in
> the remove callback.
>
Ya its nice . We can save the cpu context switching time also....
>> +
>> +static void cc2520_fifop_irqwork(struct work_struct *work)
>> +{
>> +	struct cc2520_private *priv
>> +		= container_of(work, struct cc2520_private, fifop_irqwork);
>> +
>> +	dev_dbg(&priv->spi->dev, "fifop interrupt received\n");
>> +
>> +	if (gpio_get_value(priv->fifo_pin))
>> +		cc2520_rx(priv);
>> +	else
>> +		dev_err(&priv->spi->dev, "rxfifo overflow\n");
>> +
>> +	cc2520_cmd_strobe(priv, CC2520_CMD_SFLUSHRX);
>> +	cc2520_cmd_strobe(priv, CC2520_CMD_SFLUSHRX);
>> +}
>> +
>> +static irqreturn_t cc2520_fifop_isr(int irq, void *data)
>> +{
>> +	struct cc2520_private *priv = data;
>> +
>> +	schedule_work(&priv->fifop_irqwork);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static irqreturn_t cc2520_sfd_isr(int irq, void *data)
>> +{
>> +	struct cc2520_private *priv = data;
>> +
>> +	spin_lock(&priv->lock);
> You need to use here spin_lock_irqsave and spin_unlock_irqrestore here.
> Please verify you locking with PROVE_LOCKING enabled in your kernel.
>
> In your xmit callback you use a irqsave spinlocks there. You need always
> save to the "strongest" context which is a interrupt in your case.
This type of mechanism is needed when you want to remember the interrupt 
status for the
IRQ/system.
>> +	if (priv->is_tx) {
>> +		dev_dbg(&priv->spi->dev, "SFD for TX\n");
>> +		priv->is_tx = 0;
>> +		complete(&priv->tx_complete);
>> +	} else
>> +		dev_dbg(&priv->spi->dev, "SFD for RX\n");
> make brackets in the else branch if you have brackets in the "if" branch.
>
> You don't need to lock all the things here I think:
>
> --snip
> 	spin_lock_irqsave(&priv->lock, flags);
> 	if (priv->is_tx) {
> 		priv->is_tx = 0;
> 		spin_unlock_irqrestore(&priv->lock, flags);
> 		dev_dbg(&priv->spi->dev, "SFD for TX\n");
> 		complete(&priv->tx_complete);
> 	} else {
> 		spin_unlock_irqrestore(&priv->lock, flags);
> 		dev_dbg(&priv->spi->dev, "SFD for RX\n");
> 	}
> --snap
>
Ya this can be the good approach...
>> +	spin_unlock(&priv->lock);
>> +
>> +	return IRQ_HANDLED
>> +/*Driver probe function*/
>> +static int cc2520_probe(struct spi_device *spi)
>> +{
>> +	struct cc2520_private *priv;
>> +	struct pinctrl *pinctrl;
>> +	struct cc2520_platform_data *pdata;
>> +	struct device_node __maybe_unused *np = spi->dev.of_node;
>> +	int ret;
>> +
>> +	priv = kzalloc(sizeof(struct cc2520_private), GFP_KERNEL);
>> +	if (!priv) {
>> +		ret = -ENOMEM;
>> +		goto err_free_local;
>> +	}
> why not devm_ calls?
I will surely change it to devm_....
>> +
>> +	spi_set_drvdata(spi, priv);
>> +
>> +	pinctrl = devm_pinctrl_get_select_default(&spi->dev);
>> +
>> +	if (gpio_is_valid(pdata->vreg)) {
>> +		ret = devm_gpio_request_one(&spi->dev, pdata->vreg,
>> +					GPIOF_OUT_INIT_LOW, "vreg");
>> +		if (ret)
>> +			goto err_hw_init;
>> +	}
> You should check on the not optional pins if you can request them. You
> use in the above code the pins vreg, reset, fifo_irq, sfd. And this
> failed if the gpio's are not valid.
>
> means:
>
> if (!gpio_is_valid(pdata->vreg)) {
> 	dev_err(....)
> 	ret = -EINVAL;
> 	goto ...;
> }
>
> on all pins which are needed to use your chip.
>
>> +
>> +	gpio_set_value(pdata->vreg, HIGH);
>> +	udelay(100);
>> +
>> +	gpio_set_value(pdata->reset, HIGH);
>> +	udelay(200);
>> +
>> +	ret = cc2520_hw_init(priv);
>> +	if (ret)
>> +		goto err_hw_init;
>> +
>> +	/*Set up fifop interrupt */
>> +	priv->fifo_irq = gpio_to_irq(pdata->fifop);
> why is fifo_irq in your "private data"? This is only used in this function.

Ya this is my mistake. Previously i used in other place also.

>> +	ret = devm_request_irq(&spi->dev,
>> +				priv->fifo_irq,
>> +				cc2520_fifop_isr,
>> +				IRQF_TRIGGER_RISING,
>> +				dev_name(&spi->dev),
>> +				priv);
>> +	if (ret) {
>> +		dev_err(&spi->dev, "could not get fifop irq\n");
>> +		goto err_hw_init;
>> +	}
>> +
>> +	/*Set up sfd interrupt*/
>> +	ret = devm_request_irq(&spi->dev,
>> +				gpio_to_irq(pdata->sfd),
>> +				cc2520_sfd_isr,
>> +				IRQF_TRIGGER_FALLING,
>> +				dev_name(&spi->dev),
>> +				priv);
>> +	if (ret) {
>> +		dev_err(&spi->dev, "could not get sfd irq\n");
>> +		goto err_hw_init;
>> +	}
>> +
>> +	ret = cc2520_register(priv);
>> +	if (ret)
>> +		goto err_hw_init;
>> +
>> +	return 0;
>> +
>> +err_hw_init:
>> +	mutex_destroy(&priv->buffer_mutex);
>> +	flush_work(&priv->fifop_irqwork);
>> +
>> +err_free_buf:
>> +	kfree(priv->buf);
>> +
>> +err_free_local:
>> +	kfree(priv);
>> +
>> +	return ret;
>> +}
>> +
>> +/*Driver remove function*/
>> +static int cc2520_remove(struct spi_device *spi)
>> +{
>> +	struct cc2520_private *priv = spi_get_drvdata(spi);
>> +
>> +	cc2520_unregister(priv);
>> +
>> +	mutex_destroy(&priv->buffer_mutex);
>> +	flush_work(&priv->fifop_irqwork);
>> +
>> +	kfree(priv->buf);
>> +	kfree(priv);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct spi_device_id cc2520_ids[] = {
>> +	{"cc2520", 0},
> You don't need to set the driver_data to 0. Simple:
> 	{ "cc2520", },
this does not make any difference.
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(spi, cc2520_ids);
>> +
>> +static const struct of_device_id cc2520_of_ids[] = {
>> +	{.compatible = "ti,cc2520", },
>> +	{},
>> +};
>> +MODULE_DEVICE_TABLE(of, cc2520_of_ids);
>> +
>> +/*SPI Driver Structure*/
>> +static struct spi_driver cc2520_driver = {
>> +	.driver = {
>> +		.name = "cc2520",
>> +		.bus = &spi_bus_type,
>> +		.owner = THIS_MODULE,
>> +		.of_match_table = of_match_ptr(cc2520_of_ids),
>> +	},
>> +	.id_table = cc2520_ids,
>> +	.probe = cc2520_probe,
>> +	.remove = cc2520_remove,
>> +};
>> +module_spi_driver(cc2520_driver);
>> +
>> +MODULE_DESCRIPTION("CC2520 Transceiver Driver");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/linux/spi/cc2520.h b/include/linux/spi/cc2520.h
>> new file mode 100644
>> index 0000000..68a2c88
>> --- /dev/null
>> +++ b/include/linux/spi/cc2520.h
> In this location of header files are platform_data structs only. I think
> you should leave the cc2520_platform_data in this file and move the rest
> of declaration to you cc2520.c file.
>
I will move the code
>> @@ -0,0 +1,176 @@
>> +#ifndef __CC2520_H
>> +#define __CC2520_H
>> +
>> +#define RSSI_VALID		0
>> +#define RSSI_OFFSET		78
>> +#define CC2520_FREG_MASK	0x3F
>> +
>> +struct cc2520_platform_data {
>> +	int fifo;
>> +	int fifop;
>> +	int cca;
>> +	int sfd;
>> +	int reset;
>> +	int vreg;
>> +};
>> +
> - Alex

-Varka Bhadram

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