On Tue, Sep 10, 2019 at 02:03:17AM +0000, Yoshihiro Shimoda wrote: > I'm sorry for causing this trouble on your environment. I have a proposal to > resolve this issue. The mmc_host struct will have a new caps2 flag > like MMC_CAP2_MERGE_CAPABLE and add a condition into the queue.c like below. > > + if (host->caps2 & MMC_CAP2_MERGE_CAPABLE && > + host->max_segs < MMC_DMA_MAP_MERGE_SEGMENTS && > dma_get_merge_boundary(mmc_dev(host))) > host->can_dma_map_merge = 1; > else > host->can_dma_map_merge = 0; > > After that, all mmc controllers disable the feature as default, and if a mmc > controller has such capable, the host driver should set the flag.
That sounds sensible to me. Alternatively we'd have to limit max_sectors to 16-bit values for sdhci if using an iommu that can merge.
