Data inconsistency observed while performing to-device DMA with spi-nor (m25p80)

Chetan Nanda chetannanda at
Sun Jul 26 23:58:55 EDT 2015

On Sun, Jul 26, 2015 at 5:02 PM, AYAN KUMAR HALDER <ayankumarh at>

> Hi,
> I am doing a DMA transfer (to device) using pl330 driver from
> memory(DDR) to device(m25p80, spi- nor). I am sending data in chunks
> of 256 bytes ( m25p80 - writesize) using scatter-gather mechanism.
> I see that when I try to write 8K of data, one or the other 256
> bytes(or lesser) are not written or are partially written with 0s.
> This problem is observed only when I perform a to-device DMA transfer.
> When I perform a from-device DMA transfer, I am able to read correct
> data.
There could be multiple issues like
- In buffers allocations, is the buffer used for to-device DMA is
physically contiguous?
- Caching issue, buffer should be un-cacheable.
- Any other programming error.

- Chetan Nanda

> Ayan Kumar Halder
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