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

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Message-ID: <20131003010230.GN6768@jonmason-lab>
Date:	Wed, 2 Oct 2013 18:02:30 -0700
From:	Jon Mason <jon.mason@...el.com>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Michael Ellerman <michael@...erman.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Andy King <acking@...are.com>,
	Matt Porter <mporter@...nel.crashing.org>,
	linux-pci@...r.kernel.org, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux390@...ibm.com,
	linux-s390@...r.kernel.org, x86@...nel.org,
	linux-ide@...r.kernel.org, iss_storagedev@...com,
	linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	linux-driver@...gic.com,
	Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
	"VMware, Inc." <pv-drivers@...are.com>, linux-scsi@...r.kernel.org
Subject: Re: [PATCH RFC 55/77] ntb: Update MSI/MSI-X interrupts enablement
 code

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@...hat.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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