Hi,
Tryign to use DMA to offload SPI trabnsfers for a project and have run to an issue which looks liek a cache flush related problem.
I have used kmalloc(sizeof( RxPackets), GFP_KERNEL ); to allocate a buffer and then usign the spi driver to manage the transfer, this will often work at low data rates but as data rates increase I find that data is invalid and a test pattern written to memory (before the aysnch transfer request) is not overqritten despiote completion of the spi request.
Its not clear to me if I have requested the right type of memory, or if I shoudl eb using the dma_alloc_coherent( ) interface to allocate the buffre needed and then passing in the physical address as part of the spi message.
I have seen reference to dma_alloc_coherent( ) and have trioed this but get a warning that the "spi4.0: coherent DMA mask is unset" when the driver attemtps to allocate I assume that I need to set the dma mask for the driver.
Uisng ti-dvsdk_dm3730-evm_4_01_00_09 at the monent, contemplatign updatign to the newer version but not usre it will help with this.
Questions I guess are:
1) What is the correct approach?
2) Are there any example sof this in drivers for the OMAP I can use a referebnce, can;t seem to find a good refercne to use.
All help welcome.
David
