Bug report: MIPS CI20/jz4740-mmc DMA and PREEMPT_NONE

[Aaro Koskinen]

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.