ath11k: BigEndian platform support?

[Kalle Valo]

Alexander Wilhelm <alexander.wilhelm at westermo.com> writes:

> I am trying to get the QCN9074 module to work on a BigEndian PowerPC
> platform. My question would be, has anyone done it yet? If not, what
> kind of effort would you estimate for porting or are there any
> firmware limitations?

This is a good question. The short answer is that it _might_ work with
QCN9074 but AFAIK nobody has tested it and I'm not really optimistic.

The long answer is that the big endian support in ath11k is implemented
in a weird way which I regret big time. The idea is that the firmware
does the translation instead of ath11k driver with this flag:

/* Host software's Copy Engine configuration. */
#ifdef __BIG_ENDIAN
#define CE_ATTR_FLAGS CE_ATTR_BYTE_SWAP_DATA
#else
#define CE_ATTR_FLAGS 0
#endif

But later I was told that not all firmware branches actually support
this feature, sigh. To my knowledge QCA6390 and WCN6855 firmwares do not
support this CE_ATTR_BYTE_SWAP_DATA but I'm hoping QCN9074 firmware
would support it. Grep for BIG_ENDIAN to see more big endian specific
changes.

In ath12k the endian support was implemented in a proper way using
__le32 type family and cpu_to_le32() & co macros, but it's also
untested. It's on my todo list to convert ath11k to do the same but no
idea when I'm able to work on it. Patches very welcome.

Do let me know if you test ath11k on big endian, I'm very curious to
know the results.

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