Re: [PATCH v2 27/32] scsi: hisi_sas: add smp protocol support

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On 30/10/2015 13:53, Arnd Bergmann wrote:
On Monday 26 October 2015 22:14:58 John Garry wrote:

+       /*
+       * DMA-map SMP request, response buffers
+       */
+       /* req */
+       sg_req = &task->smp_task.smp_req;
+       elem = dma_map_sg(dev, sg_req, 1, DMA_TO_DEVICE);
+       if (!elem)
+               return -ENOMEM;
+       req_len = sg_dma_len(sg_req);
+       req_dma_addr = sg_dma_address(sg_req);

If you only use the first element, could you just use dma_map_single()?


Can do. Actually sg_req seems only ever has one element:
expander.c, smp_execute_task()
sg_init_one(&task->smp_task.smp_req, req, req_size);

+       hdr->cmd_table_addr_lo = cpu_to_le32(lower_32_bits(req_dma_addr));
+       hdr->cmd_table_addr_hi = cpu_to_le32(upper_32_bits(req_dma_addr));
+
+       hdr->sts_buffer_addr_lo =
+                       cpu_to_le32(lower_32_bits(slot->status_buffer_dma));
+       hdr->sts_buffer_addr_hi =
+                       cpu_to_le32(upper_32_bits(slot->status_buffer_dma));
+


I see these a lot in your code. Could you replace this wit

	hdr->cmd_table_addr = cpu_to_le64(req_dma_addr);

This seems reasonable. They are not swapped.

and so on? That would be much more readable. Or are the two __le32 variables
swapped? If so, you could add a small helper function like

static inline __le64 cpu_to_le64_wordswapped(u64 val)
{
	return cpu_to_le64(val >> 32 | val << 32);
}

	Arnd

.


cheers


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