Re: [PATCH 1/2] ads7846: Make buffers in ads7846_read12_ser and ads7845_read12_ser DMA save

[Jonathan Cameron <jic23@cam.ac.uk>]

On 05/04/11 16:49, Jonathan Cameron wrote:
> On 05/04/11 16:22, Alexander Stein wrote:
>> req.sample needs its own cacheline otherwise accessing req.msg fetches
>> it in again.
>> Put req onto stack as it doesn't need to be DMA save.
>> req.sample is kzalloced itself for DMA access.
>> req.command doesn't need own cache line because it will only be written to
>> memory on dma_map_single. req.scratch is unsed at all.
>>
>> Note: This effect doesn't occur if the underlying SPI driver doesn't use
>> DMA at all.
>>
> How about using ____cacheline_aligned having moved 'sample' to the end of the
> structure?
> 
> e.g.
> 
> ...
> struct spi_transfer xfer[6];
> __be16  sample ____cacheline_aligned;
> }
hmm. I should probably have glanced further up the thread. Michael beat me to it
with the same suggestion!