From: Grygorii Strashko

Sent: 16 April 2021 10:27

...

Sry, for delayed reply.

The TI platforms am3/4/5 (cpsw) and Keystone 2 (netcp) can do only 32bit DMA even in case of LPAE
(dma-ranges are used).
Originally, as I remember, CONFIG_ARCH_DMA_ADDR_T_64BIT has not been selected for the LPAE case
on TI platforms and the fact that it became set is the result of multi-paltform/allXXXconfig/DMA
optimizations and unification.
(just checked - not set in 4.14)

Probable commit 4965a68780c5 ("arch: define the ARCH_DMA_ADDR_T_64BIT config symbol in lib/Kconfig").

The TI drivers have been updated, finally to accept ARCH_DMA_ADDR_T_64BIT=y by using things like
(__force u32)
for example.

Hmmm using (__force u32) is probably wrong.
If an address +length >= 2**32 can get passed then the IO request
needs to be errored (or a bounce buffer used).

Otherwise you can get particularly horrid corruptions.

	David

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