Re: [PATCH RFC 46/77] mlx4: Update MSI/MSI-X interrupts enablement code

[Jack Morgenstein <jackm@dev.mellanox.co.il>]

On Wed,  2 Oct 2013 12:49:02 +0200
Alexander Gordeev <agordeev@redhat.com> wrote:

NACK.  This change does not do anything logically as far as I can tell.
pci_enable_msix in the current upstream kernel itself calls
pci_msix_table_size.  The current code yields the same results
as the code suggested below. (i.e., the suggested code has no effect on
optimality).

BTW, pci_msix_table_size never returns a value < 0 (if msix is not
enabled, it returns 0 for the table size), so the (err < 0) check here
is not correct. (I also do not like using "err" here anyway for the
value returned by pci_msix_table_size().  There is no error here, and
it is simply confusing.

-Jack

> 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/net/ethernet/mellanox/mlx4/main.c |   17 ++++++++---------
>  1 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c
> b/drivers/net/ethernet/mellanox/mlx4/main.c index 60c9f4f..377a5ea
> 100644 --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -1852,8 +1852,16 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) int i;
>  
>  	if (msi_x) {
> +		err = pci_msix_table_size(dev->pdev);
> +		if (err < 0)
> +			goto no_msi;
> +
> +		/* Try if at least 2 vectors are available */
>  		nreq = min_t(int, dev->caps.num_eqs -
> dev->caps.reserved_eqs, nreq);
> +		nreq = min_t(int, nreq, err);
> +		if (nreq < 2)
> +			goto no_msi;
>  
>  		entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
>  		if (!entries)
> @@ -1862,17 +1870,8 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) for (i = 0; i < nreq; ++i)
>  			entries[i].entry = i;
>  
> -	retry:
>  		err = pci_enable_msix(dev->pdev, entries, nreq);
>  		if (err) {
> -			/* Try again if at least 2 vectors are
> available */
> -			if (err > 1) {
> -				mlx4_info(dev, "Requested %d
> vectors, "
> -					  "but only %d MSI-X vectors
> available, "
> -					  "trying again\n", nreq,
> err);
> -				nreq = err;
> -				goto retry;
> -			}
>  			kfree(entries);
>  			goto no_msi;
>  		}