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Re: [PATCH RFC 55/77] ntb: Update MSI/MSI-X interrupts enablement code

To: Alexander Gordeev <agordeev@redhat.com>
Subject: Re: [PATCH RFC 55/77] ntb: Update MSI/MSI-X interrupts enablement code
From: Jon Mason <jon.mason@intel.com>
Date: Wed, 2 Oct 2013 18:02:30 -0700
Cc: linux-kernel@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>, Ralf Baechle <ralf@linux-mips.org>, Michael Ellerman <michael@ellerman.id.au>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Ingo Molnar <mingo@redhat.com>, Tejun Heo <tj@kernel.org>, Dan Williams <dan.j.williams@intel.com>, Andy King <acking@vmware.com>, Matt Porter <mporter@kernel.crashing.org>, linux-pci@vger.kernel.org, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux390@de.ibm.com, linux-s390@vger.kernel.org, x86@kernel.org, linux-ide@vger.kernel.org, iss_storagedev@hp.com, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, netdev@vger.kernel.org, e1000-devel@lists.sourceforge.net, linux-driver@qlogic.com, Solarflare linux maintainers <linux-net-drivers@solarflare.com>, "VMware, Inc." <pv-drivers@vmware.com>, linux-scsi@vger.kernel.org
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References: <cover.1380703262.git.agordeev@redhat.com> <49eb592e15aaec804f9c11ca132d2b85c516aefa.1380703263.git.agordeev@redhat.com>
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On Wed, Oct 02, 2013 at 12:49:11PM +0200, Alexander Gordeev wrote:
> As result of recent re-design of the MSI/MSI-X interrupts enabling
> pattern this driver has to be updated to use the new technique to
> obtain a optimal number of MSI/MSI-X interrupts required.
> 
> Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
> ---
>  drivers/ntb/ntb_hw.c |   41 +++++++++++++----------------------------
>  drivers/ntb/ntb_hw.h |    2 --
>  2 files changed, 13 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
> index eccd5e5..7776429 100644
> --- a/drivers/ntb/ntb_hw.c
> +++ b/drivers/ntb/ntb_hw.c
> @@ -1032,23 +1032,26 @@ static int ntb_setup_msix(struct ntb_device *ndev)
>       struct msix_entry *msix;
>       int msix_entries;
>       int rc, i;
> -     u16 val;
>  
> -     if (!pdev->msix_cap) {
> -             rc = -EIO;
> +     rc = pci_msix_table_size(pdev);
> +     if (rc < 0)
>               goto err;
> -     }
>  
> -     rc = pci_read_config_word(pdev, pdev->msix_cap + PCI_MSIX_FLAGS, &val);
> -     if (rc)
> +     /*
> +      * 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 ((rc < SNB_MSIX_CNT) && (ndev->hw_type != BWD_HW)) {

Please check for the HW type first, and then compare to
ndev->limits.msix_cnt (which will be SNB_MSIX_CNT on SNB HW).  Also,
put the comment inside the if statement and remove the unecessary "()"
around the comparisons.  OCD on my part, but I like it that way.  

> +             rc = -ENOSPC;
>               goto err;
> -
> -     msix_entries = msix_table_size(val);
> -     if (msix_entries > ndev->limits.msix_cnt) {
> +     }

else if...

> +     if (rc > ndev->limits.msix_cnt) {
>               rc = -EINVAL;
>               goto err;
>       }
>  
> +     msix_entries = rc;
> +
>       ndev->msix_entries = kmalloc(sizeof(struct msix_entry) * msix_entries,
>                                    GFP_KERNEL);
>       if (!ndev->msix_entries) {
> @@ -1060,26 +1063,8 @@ static int ntb_setup_msix(struct ntb_device *ndev)
>               ndev->msix_entries[i].entry = i;
>  
>       rc = pci_enable_msix(pdev, ndev->msix_entries, msix_entries);
> -     if (rc < 0)
> +     if (rc)
>               goto err1;
> -     if (rc > 0) {
> -             /* 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 ((rc < SNB_MSIX_CNT) && (ndev->hw_type != BWD_HW)) {
> -                     rc = -EIO;
> -                     goto err1;
> -             }
> -
> -             dev_warn(&pdev->dev,
> -                      "Only %d MSI-X vectors.  Limiting the number of queues 
> to that number.\n",
> -                      rc);
> -             msix_entries = rc;
> -
> -             rc = pci_enable_msix(pdev, ndev->msix_entries, msix_entries);
> -             if (rc)
> -                     goto err1;
> -     }
>  
>       for (i = 0; i < msix_entries; i++) {
>               msix = &ndev->msix_entries[i];
> diff --git a/drivers/ntb/ntb_hw.h b/drivers/ntb/ntb_hw.h
> index 0a31ced..50bd760 100644
> --- a/drivers/ntb/ntb_hw.h
> +++ b/drivers/ntb/ntb_hw.h
> @@ -60,8 +60,6 @@
>  #define PCI_DEVICE_ID_INTEL_NTB_SS_HSX               0x2F0F
>  #define PCI_DEVICE_ID_INTEL_NTB_B2B_BWD              0x0C4E
>  
> -#define msix_table_size(control)     ((control & PCI_MSIX_FLAGS_QSIZE)+1)

Good riddance!  :-)

> -
>  #ifndef readq
>  static inline u64 readq(void __iomem *addr)
>  {
> -- 
> 1.7.7.6
> 

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