[PATCH v2 0/2] mmc: dw_mmc: fix DW MMC cores with 32-bit bus on 64-bit Linux systems

Sergey Lisov
2023-03-11T18:22:32Z

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.

Sergey Lisov (2):
dt-bindings: synopsys-dw-mshc-common: add "fifo-access-32bit" property
mmc: dw_mmc: add an option to force 32-bit access to 64-bit FIFO

.../bindings/mmc/synopsys-dw-mshc-common.yaml | 7 +
drivers/mmc/host/dw_mmc.c | 125 +++++++++++++++++-
drivers/mmc/host/dw_mmc.h | 2 +
3 files changed, 132 insertions(+), 2 deletions(-)

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2.38.3