From: Alexander Duyck

Sent: 05 December 2016 21:55

...

quoted

@@ -1010,6 +1018,11 @@ int i40e_setup_tx_descriptors(struct i40e_ring *tx_ring)
         */
        tx_ring->size += sizeof(u32);
        tx_ring->size = ALIGN(tx_ring->size, 4096);
+#ifdef CONFIG_SPARC
+       tx_ring->dma_attrs = DMA_ATTR_WEAK_ORDERING;
+#else
+       tx_ring->dma_attrs = 0;
+#endif
        tx_ring->desc = dma_alloc_coherent(dev, tx_ring->size,
                                           &tx_ring->dma, GFP_KERNEL);
        if (!tx_ring->desc) {

Also not a fan of adding yet ring attribute.  Is there any reason why
you couldn't simply add a set of inline functions at the start of
i40e_txrx.c that could replace the DMA map/unmap operations in this
code but pass either 0 or DMA_ATTR_WEAK_ORDERING as needed for the
drivers?  Then the x86 code doesn't have to change while the SPARC
code will be able to be passed the attribute.

Or use something like:
#ifdef CONFIG_SPARC
       #define RING_DMA_ATTR DMA_ATTR_WEAK_ORDERING
#else
       #define RING_DMA_ATTR 0
#endif
and pass the constant to the function calls.

Is there actually ever a problem passing DMA_ATTR_WEAK_ORDERING?
I'd guess that it will be ignored if it can't be implemented (or isn't needed).

	David