[PATCH v2 0/2] Configuring DMA threshold value for DW-MMC controllers

[Kaustabh Chakraborty]

In Samsung Exynos 7870 devices with Broadcom Wi-Fi, it has been observed
that small sized DMA transfers are unreliable and are not written
properly, which renders the cache incoherent.

Experimental observations say that DMA transfer sizes of somewhere
around 64 to 512 are intolerable. We must thus implement a mechanism to
fall back to PIO transfer in this case. One such approach, which this
series implements is allowing the DMA transfer threshold, which is
already defined in the driver, to be configurable.

Note that this patch is likely to be labelled as a workaround. These
smaller transfers seem to be successful from downstream kernels,
however efforts to figure out how so went in vain. It is also very
possible that the downstream Broadcom Wi-Fi SDIO driver uses PIO
transfers as well.

Signed-off-by: Kaustabh Chakraborty <kauschluss@xxxxxxxxxxx>
---
Changes in v2:
- Remove dt-binding to set DMA threshold (Krzysztof Kozlowski)
- Add comment to describe struct dw_mci::dma_threshold (Shawn Lin)
- Set DMA threshold in Exynos 7870 DW-MMC driver (Krzysztof Kozlowski)
- Link to v1: https://lore.kernel.org/r/20260412-dwmmc-dma-thr-v1-0-75a2f658eee3@xxxxxxxxxxx

---
Kaustabh Chakraborty (2):
      mmc: dw_mmc: implement option for configuring DMA threshold
      mmc: dw_mmc: exynos: increase DMA threshold value for exynos7870

 drivers/mmc/host/dw_mmc-exynos.c | 1 +
 drivers/mmc/host/dw_mmc.c        | 5 +++--
 drivers/mmc/host/dw_mmc.h        | 2 ++
 3 files changed, 6 insertions(+), 2 deletions(-)
---
base-commit: 1c7cc4904160c6fc6377564140062d68a3dc93a0
change-id: 20260412-dwmmc-dma-thr-1090d8285ea7

Best regards,
-- 
Kaustabh Chakraborty <kauschluss@xxxxxxxxxxx>