On Sat, Aug 9, 2008 at 11:20 AM, Stefan Richter
<stefanr@xxxxxxxxxxxxxxxxx> wrote:
> 1. We don't need to round the SBP-2 segment size limit down to a
> multiple of 4 kB (0xffff -> 0xf000). It is only necessary to
> ensure quadlet alignment (0xffff -> 0xfffc).
>
> 2. Use dma_set_max_seg_size() to tell the DMA mapping infrastructure
> and the block IO layer about the restriction. This way we can
> remove the size checks and segment splitting in the queuecommand
> path.
>
> This assumes that no other code in the ieee1394 stack uses
> dma_map_sg() with conflicting requirements. It furthermore assumes
> that the controller device's platform actually allows us to set the
> segment size to our liking. Assert the latter with a BUG_ON().
>
> 3. Also use blk_queue_max_segment_size() to tell the block IO layer
> about it. It cannot know it because our scsi_add_host() does not
> point to the FireWire controller's device.
>
> We can also uniformly use dma_map_sg() for the single segment case just
> like for the multi segment case, to further simplify the code.
>
> Also clean up how the page table is converted to big endian.
>
> Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
> ---
>
> Applicable after
> [PATCH update] ieee1394: sbp2: stricter dma_sync
> [PATCH] ieee1394: sbp2: check for DMA mapping failures
> from a few minutes ago.
>
> drivers/ieee1394/sbp2.c | 106 +++++++++++++---------------------------
> drivers/ieee1394/sbp2.h | 37 +++++--------
> 2 files changed, 52 insertions(+), 91 deletions(-)
...
> + for_each_sg(sg, sg, sg_count, i) {
> + len = sg_dma_len(sg);
> + if (len == 0)
> + continue;
>
> - orb->misc |= ORB_SET_DATA_SIZE(sg_count);
> + pt[j].high = cpu_to_be32(len << 16);
> + pt[j].low = cpu_to_be32(sg_dma_address(sg));
> + j++;
> + }
While this code will probably work correctly, I believe if the
sg_dma_len() returns 0, one has walked off the end of the
"bus address" list.
pci_map_sg() returns how many DMA addr/len pairs are used
and that count could (should?) be used when pulling the
dma_len/addr pairs out of the sg list.
Effectively, the SG list is really two lists with seperate counts:
the original list with virtual addresses/len/count and the "DMA mapped"
list with it's own count of addresses/len pairs. When no IOMMU
is used those lists are 1:1.
hth,
grant
> - sbp2util_cpu_to_be32_buffer(sg_element,
> - (sizeof(struct sbp2_unrestricted_page_table)) *
> - sg_count);
> + orb->misc |= ORB_SET_PAGE_TABLE_PRESENT(0x1) |
> + ORB_SET_DATA_SIZE(j);
> + orb->data_descriptor_lo = cmd->sge_dma;
>
> dma_sync_single_for_device(dmadev, cmd->sge_dma,
> sizeof(cmd->scatter_gather_element),
> @@ -2037,6 +2003,8 @@ static int sbp2scsi_slave_configure(stru
> sdev->start_stop_pwr_cond = 1;
> if (lu->workarounds & SBP2_WORKAROUND_128K_MAX_TRANS)
> blk_queue_max_sectors(sdev->request_queue, 128 * 1024 / 512);
> +
> + blk_queue_max_segment_size(sdev->request_queue, SBP2_MAX_SEG_SIZE);
> return 0;
> }
>
>
> --
> Stefan Richter
> -=====-==--- =--- -=--=
> http://arcgraph.de/sr/
>
>
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