DesignWare MMC cores have a configurable data bus width of either 16, 32, or 64
bytes. It is possible, and some vendors actually do it, to ship a DW MMC core
configured for 32-bit data bus within a 64-bit SoC. In this case the kernel
will attempt 64-bit (readq) accesses to certain 64-bit MMIO registers, while
the core will expect pairs of 32-bit accesses.
It seems that currently the only register for which the kernel performs 64-bit
accesses is the FIFO. The symptom is that the DW MMC core never receives a read
on the second half of the register, does not register the datum as being read,
and thus not advancing its internal FIFO pointer, breaking further reads. It
also seems that this FIFO is only used for small (less than 16 bytes)
transfers, which probably means that only some SDIO cards are affected.
Changelog:
v4:
- split dt-bindings and dts update into separate commits
- add an explanation why it'ss necessary to change the compatible string
v3:
- removed "fifo-access-32bit" devicetree property
- added "samsung,exynos78xx-dw-mshc" compatible string
- added "samsung,exynos78xx-dw-mshc-smu" compatible string
v2:
- added commit messages
v1:
- added "fifo-access-32bit" devicetree property
- added DW_MMC_QUIRK_FIFO64_32
- added new dw_mci_{pull,push}_data* variants (...-data64_32)
Sergey Lisov (3):
dt-bindings: exynos-dw-mshc-common: add exynos78xx variants
arm64: dts: exynos: fix wrong mmc compatible in exynos7885.dtsi
mmc: dw_mmc: add an option to force 32-bit access to 64-bit FIFO
.../bindings/mmc/samsung,exynos-dw-mshc.yaml | 2 +
arch/arm64/boot/dts/exynos/exynos7885.dtsi | 2 +-
drivers/mmc/host/dw_mmc-exynos.c | 41 +++++-
drivers/mmc/host/dw_mmc.c | 122 +++++++++++++++++-
drivers/mmc/host/dw_mmc.h | 2 +
5 files changed, 165 insertions(+), 4 deletions(-)
--
2.38.3
