On Sun, Jul 26, 2015 at 5:02 PM, AYAN KUMAR HALDER <ayankumarh@gmail.com> wrote:

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

Regards,
Ayan Kumar Halder

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