On Mon, Feb 06, 2023 at 08:41:41AM -0700, Jeffrey Hugo wrote:
> + * It turns out several of the iommu drivers don't combine adjacent
> + * regions, which is really what we expect based on the description of
> + * dma_map_sgtable(), so lets see if that can be done. It makes our message
> + * more efficent.
> + */
Interesting ...
> + last = sgt->sgl;
> + nents_dma = nents;
> + size = QAIC_MANAGE_EXT_MSG_LENGTH - msg_hdr_len - sizeof(*out_trans);
> + for_each_sgtable_sg(sgt, sg, i) {
> + if (sg_dma_address(last) + sg_dma_len(last) !=
> + sg_dma_address(sg)) {
> + size -= sizeof(*asp);
> + /* Save 1K for possible follow-up transactions. */
> + if (size < SZ_1K) {
> + nents_dma = i;
> + break;
> + }
> + }
> + last = sg;
> + }
I would say there is reason why iommu do not combine or there is problem in iommu driver.
If there is reason for not-combining this code is wrong.
If problem is in iommu driver why not fixup iommu ?
And why not create sg list that don't have adjacent entries in the first place ?
Regards
Stanislaw
