Hi, There is something wrong with jz4740-mmc in current mainline kernel (tested v4.18 and 4.19-rc, the MMC support for CI20 does not exist prior those), as the DMA support does not work properly if I disable kernel pre-emption. The console gets flooded with: [ 16.461094] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 567 host->next_data.cookie 568 [ 16.473120] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 568 host->next_data.cookie 569 [ 16.485144] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 569 host->next_data.cookie 570 [ 16.497170] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 570 host->next_data.cookie 571 [ 16.509194] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 571 host->next_data.cookie 572 [ 16.532421] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 572 host->next_data.cookie 573 [ 16.544594] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 573 host->next_data.cookie 574 [ 16.556621] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 574 host->next_data.cookie 575 [ 16.568638] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 575 host->next_data.cookie 576 [ 16.601092] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 582 host->next_data.cookie 583 etc. ad inf. This should be easily reproducible on CI20 board with ci20_defconfig and setting CONFIG_PREEMPT_NONE=y. A.
