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igb: Use dma_wmb() instead of wmb() before doorbell writes 

igb writes to doorbells to post transmit and receive descriptors;
after writing descriptors to memory but before writing to doorbells,
use dma_wmb() rather than wmb(). wmb() is more heavyweight than
necessary before doorbell writes.

On x86, this avoids SFENCEs before doorbell writes in both the
tx and rx refill paths.

Signed-off-by: Venkatesh Srinivas <venkateshs@google.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Venkatesh Srinivas 2018-05-25 00:13:21 -04:00 committed by Jeff Kirsher
parent 2a83fba6ca
commit 73017f4e05
1 changed files with 2 additions and 2 deletions
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4
drivers/net/ethernet/intel/igb/igb_main.c
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@ -6031,7 +6031,7 @@ static int igb_tx_map(struct igb_ring *tx_ring,
* We also need this memory barrier to make certain all of the
* status bits have been updated before next_to_watch is written.
*/
wmb();
dma_wmb();
/* set next_to_watch value indicating a packet is present */
first->next_to_watch = tx_desc;
@ -8531,7 +8531,7 @@ void igb_alloc_rx_buffers(struct igb_ring *rx_ring, u16 cleaned_count)
* applicable for weak-ordered memory model archs,
* such as IA-64).
*/
wmb();
dma_wmb();
writel(i, rx_ring->tail);
}
}