RE: [PATCH 1/1] qlcnic: add wmb() call in transmit data path.

Subject: Re: [PATCH 1/1] qlcnic: add wmb() call in transmit data path.

quoted

+    /* Ensure writes are complete before HW fetches Tx descriptors */
+    wmb();
      qlcnic_update_cmd_producer(tx_ring);

      return NETDEV_TX_OK;

Would not an mmiowb be more appropriate in this case?

Regards,
Lino

Sorry, this was nonsense.This should be "dma_wmb" not "mmiowb".

Lino,

The patch is based on this kernel documentation. 

https://www.kernel.org/doc/Documentation/memory-barriers.txt
	
	/* force memory to sync before notifying device via MMIO */
		wmb();

		/* notify device of new descriptors */
		writel(DESC_NOTIFY, doorbell);
	}
The wmb() is needed to guarantee that the cache coherent memory writes have 
completed before attempting a write to the cache incoherent MMIO region.

Thanks,
Sony