Re: [PATCH v5 4/4] fm10k/igb/ixgbe: Use dma_rmb on Rx descriptor reads

Jeff Kirsher
2014-11-19T01:28:52Z

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On Tue, 2014-11-18 at 17:24 -0800, Alexander Duyck wrote:
> This change makes it so that dma_rmb is used when reading the Rx
> descriptor. The advantage of dma_rmb is that it allows for a much
> lower cost barrier on x86, powerpc, arm, and arm64 architectures than
> a
> traditional memory barrier when dealing with reads that only have to
> synchronize to coherent memory.
>
> In addition I have updated the code so that it just checks to see if
> any
> bits have been set instead of just the DD bit since the DD bit will
> always
> be set as a part of a descriptor write-back so we just need to check
> for a
> non-zero value being present at that memory location rather than just
> checking for any specific bit. This allows the code itself to appear
> much
> cleaner and allows the compiler more room to optimize.
>
> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Cc: Matthew Vick <matthew.vick@intel.com>
> Cc: Don Skidmore <donald.c.skidmore@intel.com>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
> ---
> drivers/net/ethernet/intel/fm10k/fm10k_main.c | 6 +++---
> drivers/net/ethernet/intel/igb/igb_main.c | 6 +++---
> drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 9 ++++-----
> 3 files changed, 10 insertions(+), 11 deletions(-)

Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

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