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Date: Wed, 10 Oct 2012 10:06:32 -0700
From: Jon Mason <jon.mason@...el.com>
To: Jakub Kicinski <kubakici@...pl>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-pci@...r.kernel.org, Dave Jiang <dave.jiang@...el.com>,
Nicholas Bellinger <nab@...ingtidesystems.com>
Subject: Re: [1/2] PCI-Express Non-Transparent Bridge Support
On Sun, Oct 07, 2012 at 02:13:44PM +0200, Jakub Kicinski wrote:
> Hi,
>
> it's good to see some NTB code getting into mainline! I have a few comments
> though.
>
> On Tue, 02 Oct 2012 21:26:16 -0000, Jon Mason <jon.mason@...el.com>
> wrote:
>
> [...]
> >+/**
> >+ * ntb_write_local_spad() - write to the secondary scratchpad register
> >+ * @ndev: pointer to ntb_device instance
> >+ * @idx: index to the scratchpad register, 0 based
> >+ * @val: the data value to put into the register
> >+ *
> >+ * This function allows writing of a 32bit value to the indexed scratchpad
> >+ * register. The register resides on the secondary (external) side.
> >+ *
> >+ * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
> >+ */
> [...]
> >+/**
> >+ * ntb_write_remote_spad() - write to the secondary scratchpad register
> >+ * @ndev: pointer to ntb_device instance
> >+ * @idx: index to the scratchpad register, 0 based
> >+ * @val: the data value to put into the register
> >+ *
> >+ * This function allows writing of a 32bit value to the indexed scratchpad
> >+ * register. The register resides on the secondary (external) side.
> >+ *
> >+ * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
> >+ */
>
> Those comments look suspiciously similar. I think one of the functions
> does write to primary scratchpad?
Yes, the comments can be improved.
>
> [...]
> >+/**
> >+ * ntb_read_local_spad() - read from the primary scratchpad register
> >+ * @ndev: pointer to ntb_device instance
> >+ * @idx: index to scratchpad register, 0 based
> >+ * @val: pointer to 32bit integer for storing the register value
> >+ *
> >+ * This function allows reading of the 32bit scratchpad register on
> >+ * the primary (internal) side.
> >+ *
> >+ * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
> >+ */
> [...]
> >+/**
> >+ * ntb_read_remote_spad() - read from the primary scratchpad register
> >+ * @ndev: pointer to ntb_device instance
> >+ * @idx: index to scratchpad register, 0 based
> >+ * @val: pointer to 32bit integer for storing the register value
> >+ *
> >+ * This function allows reading of the 32bit scratchpad register on
> >+ * the primary (internal) side.
> >+ *
> >+ * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
> >+ */
>
> Same here.
>
> [...]
> >+static int ntb_setup_msix(struct ntb_device *ndev)
> >+{
> >+ struct pci_dev *pdev = ndev->pdev;
> >+ struct msix_entry *msix;
> >+ int msix_entries;
> >+ int rc, i, pos;
> >+ u16 val;
> >+
> >+ pos = pci_find_capability(pdev, PCI_CAP_ID_MSIX);
> >+ if (!pos) {
> >+ rc = -EIO;
> >+ goto err;
> >+ }
> >+
> >+ rc = pci_read_config_word(pdev, pos + PCI_MSIX_FLAGS, &val);
> >+ if (rc)
> >+ goto err;
> >+
> >+ msix_entries = msix_table_size(val);
> >+ if (msix_entries > ndev->limits.msix_cnt) {
> >+ rc = -EINVAL;
> >+ goto err;
> >+ }
> >+
> >+ ndev->msix_entries = kmalloc(sizeof(struct msix_entry) * msix_entries,
> >+ GFP_KERNEL);
> >+ if (!ndev->msix_entries) {
> >+ rc = -ENOMEM;
> >+ goto err;
> >+ }
> >+
> >+ for (i = 0; i < msix_entries; i++)
> >+ ndev->msix_entries[i].entry = i;
> >+
> >+ rc = pci_enable_msix(pdev, ndev->msix_entries, msix_entries);
> >+ if (rc < 0)
> >+ goto err1;
> >+ if (rc > 0) {
>
> rc > 0 doesn't mean that vectors were allocated. Have a look at the
> example in Documentation/PCI/MSI-HOWTO.txt.
Thank you, I will correct this.
>
> >+ /* On SNB, the link interrupt is always tied to 4th vector. If
> >+ * we can't get all 4, then we can't use MSI-X.
> >+ */
> >+ if (ndev->hw_type != BWD_HW) {
> >+ rc = -EIO;
> >+ goto err1;
> >+ }
>
> This looks fragile, what if msix_table_size(val) was < 4?
If there are not at least 4 vectors, then we shouldn't use MSI-X.
>
> >+
> >+ dev_warn(&pdev->dev,
> >+ "Only %d MSI-X vectors. Limiting the number of queues to that number.\n",
> >+ rc);
> >+ msix_entries = rc;
> >+ }
> >+
> >+ for (i = 0; i < msix_entries; i++) {
> >+ msix = &ndev->msix_entries[i];
> >+ WARN_ON(!msix->vector);
> >+
> >+ /* Use the last MSI-X vector for Link status */
> >+ if (ndev->hw_type == BWD_HW) {
> >+ rc = request_irq(msix->vector, bwd_callback_msix_irq, 0,
> >+ "ntb-callback-msix", &ndev->db_cb[i]);
> >+ if (rc)
> >+ goto err2;
> >+ } else {
> >+ if (i == msix_entries - 1) {
> >+ rc = request_irq(msix->vector,
> >+ xeon_event_msix_irq, 0,
> >+ "ntb-event-msix", ndev);
> >+ if (rc)
> >+ goto err2;
> >+ } else {
> >+ rc = request_irq(msix->vector,
> >+ xeon_callback_msix_irq, 0,
> >+ "ntb-callback-msix",
> >+ &ndev->db_cb[i]);
> >+ if (rc)
> >+ goto err2;
> >+ }
> >+ }
> >+ }
> >+
> >+ ndev->num_msix = msix_entries;
> >+ if (ndev->hw_type == BWD_HW)
> >+ ndev->max_cbs = msix_entries;
> >+ else
> >+ ndev->max_cbs = msix_entries - 1;
> >+
> >+ return 0;
> >+
> >+err2:
> >+ while (--i >= 0) {
> >+ msix = &ndev->msix_entries[i];
> >+ if (ndev->hw_type != BWD_HW && i == ndev->num_msix - 1)
> >+ free_irq(msix->vector, ndev);
> >+ else
> >+ free_irq(msix->vector, &ndev->db_cb[i]);
> >+ }
> >+ pci_disable_msix(pdev);
> >+err1:
> >+ kfree(ndev->msix_entries);
> >+ dev_err(&pdev->dev, "Error allocating MSI-X interrupt\n");
> >+err:
> >+ ndev->num_msix = 0;
> >+ return rc;
> >+}
>
> Thanks for your work,
Thanks for the review.
>
> -- Kuba
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