Message-ID: <20090513162014.1f5c1bb1@bike.lwn.net>
Date:	Wed, 13 May 2009 16:20:14 -0600
From:	Jonathan Corbet <corbet@....net>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Per Dalen <per.dalen@....se>,
	Wolfgang Grandegger <wg@...ndegger.com>
Subject: Re: [PATCH v2 7/7] [PATCH 7/8] can: SJA1000 driver for Kvaser PCI
 cards

On Tue, 12 May 2009 11:28:04 +0200
Wolfgang Grandegger <wg@...ndegger.com> wrote:

> The patch adds support for the PCI cards: PCIcan and PCIcanx
> (1, 2 or 4 channel) from Kvaser (http://www.kvaser.com).

> +static void kvaser_pci_disable_irq(struct net_device *dev)
> +{
> +	struct sja1000_priv *priv = netdev_priv(dev);
> +	struct kvaser_pci *board = priv->priv;
> +	u32 tmp;

I've seen certain reviewers getting grumpy about variables called "tmp"
recently.  

> +	/* Disable interrupts from card */
> +	tmp = ioread32(board->conf_addr + S5920_INTCSR);
> +	tmp &= ~INTCSR_ADDON_INTENABLE_M;
> +	iowrite32(tmp, board->conf_addr + S5920_INTCSR);
> +}

[...]

> +static int number_of_sja1000_chip(void __iomem *base_addr)
> +{
> +	u8 status;
> +	int i;
> +
> +	for (i = 0; i < MAX_NO_OF_CHANNELS; i++) {
> +		/* reset chip */
> +		iowrite8(MOD_RM, base_addr +
> +			 (i * KVASER_PCI_PORT_BYTES) + REG_MOD);
> +		status = ioread8(base_addr +
> +				 (i * KVASER_PCI_PORT_BYTES) + REG_MOD);
> +		udelay(10);
> +		/* check reset bit */
> +		if (!(status & MOD_RM))
> +			break;

Why would you delay before checking status?  It ain't gonna change.

> +	}
> +
> +	return i;
> +}
> +
> +static void kvaser_pci_del_chan(struct net_device *dev)
> +{
> +	struct sja1000_priv *priv;
> +	struct kvaser_pci *board;
> +	int i;
> +
> +	if (!dev)
> +		return;
> +	priv = netdev_priv(dev);
> +	if (!priv)
> +		return;

Can this happen?

> +	board = priv->priv;
> +	if (!board)
> +		return;
> +
> +	dev_info(&board->pci_dev->dev, "Removing device %s\n",
> +		 dev->name);
> +
> +	for (i = 0; i < board->no_channels - 1; i++) {
> +		if (board->slave_dev[i]) {
> +			dev_info(&board->pci_dev->dev, "Removing device %s\n",
> +				 board->slave_dev[i]->name);
> +			unregister_sja1000dev(board->slave_dev[i]);
> +			free_sja1000dev(board->slave_dev[i]);
> +		}
> +	}
> +	unregister_sja1000dev(dev);
> +
> +	/* Disable PCI interrupts */
> +	kvaser_pci_disable_irq(dev);

It seems to me like you might want to disable interrupts *before* tearing
down all that structure?  What happens if it interrupts after the sja1000
layer has forgotten about it?

> +	pci_iounmap(board->pci_dev, (void __iomem *)dev->base_addr);
> +	pci_iounmap(board->pci_dev, board->conf_addr);
> +	pci_iounmap(board->pci_dev, board->res_addr);
> +
> +	free_sja1000dev(dev);
> +}
> +
> +static int kvaser_pci_add_chan(struct pci_dev *pdev, int channel,
> +			       struct net_device **master_dev,
> +			       void __iomem *conf_addr,
> +			       void __iomem *res_addr,
> +			       unsigned long base_addr)
> +{
> +	struct net_device *dev;
> +	struct sja1000_priv *priv;
> +	struct kvaser_pci *board;
> +	int err, init_step;
> +
> +	dev = alloc_sja1000dev(sizeof(struct kvaser_pci));
> +	if (dev == NULL)
> +		return -ENOMEM;
> +
> +	priv = netdev_priv(dev);

Here you don't have the !priv check.

> +	board = priv->priv;
> +
> +	board->pci_dev = pdev;
> +	board->channel = channel;
> +
> +	/*S5920*/
> +	board->conf_addr = conf_addr;
> +
> +	/*XILINX board wide address*/
> +	board->res_addr = res_addr;
> +
> +	if (channel == 0) {
> +		board->xilinx_ver =
> +			ioread8(board->res_addr + XILINX_VERINT) >> 4;
> +		init_step = 2;
> +
> +		/* Assert PTADR# - we're in passive mode so the other bits are
> +		   not important */
> +		iowrite32(0x80808080UL, board->conf_addr + S5920_PTCR);
> +
> +		/* Disable interrupts from card */
> +		kvaser_pci_disable_irq(dev);
> +		/* Enable interrupts from card */
> +		kvaser_pci_enable_irq(dev);

I'm sure there's a perfectly good reason for the disable/enable dance.
Presumably the hardware needs it or it misbehaves?  Worth commenting.

> +	} else {
> +		struct sja1000_priv *master_priv = netdev_priv(*master_dev);
> +		struct kvaser_pci *master_board = master_priv->priv;
> +		master_board->slave_dev[channel - 1] = dev;
> +		master_board->no_channels = channel + 1;
> +		board->xilinx_ver = master_board->xilinx_ver;
> +	}
> +
> +	dev->base_addr = base_addr + channel * KVASER_PCI_PORT_BYTES;
> +
> +	priv->read_reg = kvaser_pci_read_reg;
> +	priv->write_reg = kvaser_pci_write_reg;
> +
> +	priv->can.clock.freq = KVASER_PCI_CAN_CLOCK;
> +
> +	priv->ocr = KVASER_PCI_OCR;
> +	priv->cdr = KVASER_PCI_CDR;
> +
> +	/* Register and setup interrupt handling */
> +	dev->irq = pdev->irq;
> +	init_step = 4;
> +
> +	dev_info(&pdev->dev, "base_addr=%#lx conf_addr=%p irq=%d\n",
> +		 dev->base_addr, board->conf_addr, dev->irq);
> +
> +	SET_NETDEV_DEV(dev, &pdev->dev);
> +
> +	/* Register SJA1000 device */
> +	err = register_sja1000dev(dev);
> +	if (err) {
> +		dev_err(&pdev->dev, "Registering device failed (err=%d)\n",
> +			err);
> +		goto failure;
> +	}
> +
> +	if (channel == 0)
> +		*master_dev = dev;
> +
> +	return 0;
> +
> +failure:
> +	kvaser_pci_del_chan(dev);
> +	return err;
> +}
> +
> +static int __devinit kvaser_pci_init_one(struct pci_dev *pdev,
> +					 const struct pci_device_id *ent)
> +{
> +	int err;
> +	struct net_device *master_dev = NULL;
> +	struct sja1000_priv *priv;
> +	struct kvaser_pci *board;
> +	int no_channels;
> +	void __iomem *base_addr = NULL;
> +	void __iomem *conf_addr = NULL;
> +	void __iomem *res_addr = NULL;
> +	int i;
> +
> +	dev_info(&pdev->dev, "initializing device %04x:%04x\n",
> +		 pdev->vendor, pdev->device);
> +
> +	err = pci_enable_device(pdev);
> +	if (err)
> +		goto failure;
> +
> +	err = pci_request_regions(pdev, DRV_NAME);
> +	if (err)
> +		goto failure_release_pci;
> +
> +	/*S5920*/
> +	conf_addr = pci_iomap(pdev, 0, PCI_CONFIG_PORT_SIZE);
> +	if (conf_addr == NULL) {
> +		err = -ENODEV;
> +		goto failure_iounmap;

Why go there?  You know there's nothing to unmap.

> +	}
> +
> +	/*XILINX board wide address*/
> +	res_addr = pci_iomap(pdev, 2, PCI_PORT_XILINX_SIZE);
> +	if (res_addr == NULL) {
> +		err = -ENOMEM;
> +		goto failure_iounmap;
> +	}
> +
> +	base_addr = pci_iomap(pdev, 1, PCI_PORT_SIZE);
> +	if (base_addr == NULL) {
> +		err = -ENOMEM;
> +		goto failure_iounmap;
> +	}
> +
> +	no_channels = number_of_sja1000_chip(base_addr);
> +	if (no_channels == 0) {
> +		err = -ENOMEM;
> +		goto failure_iounmap;
> +	}
> +
> +	for (i = 0; i < no_channels; i++) {
> +		err = kvaser_pci_add_chan(pdev, i, &master_dev,
> +					  conf_addr, res_addr,
> +					  (unsigned long)base_addr);
> +		if (err)
> +			goto failure_cleanup;
> +	}
> +
> +	priv = netdev_priv(master_dev);
> +	board = priv->priv;
> +
> +	dev_info(&pdev->dev, "xilinx version=%d number of channels=%d\n",
> +		 board->xilinx_ver, board->no_channels);
> +
> +	pci_set_drvdata(pdev, master_dev);
> +	return 0;
> +
> +failure_cleanup:
> +	kvaser_pci_del_chan(master_dev);
> +
> +failure_iounmap:
> +	if (conf_addr == NULL)
> +		pci_iounmap(pdev, conf_addr);
> +	if (res_addr == NULL)
> +		pci_iounmap(pdev, res_addr);
> +	if (base_addr == NULL)
> +		pci_iounmap(pdev, base_addr);
> +
> +	pci_release_regions(pdev);
> +
> +failure_release_pci:
> +	pci_disable_device(pdev);
> +
> +failure:
> +	return err;
> +
> +}

jon
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