Hello, Am Mittwoch, 4. Mai 2011, 17:49:56 schrieb Jonathan Cameron: > 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; > } > > Rather smaller patch when you get down to it. Mh, I didn't know I had to reorder the struct elements to use ____cacheline_aligned. I originally had a solution in mind with a smaller memory footprint in mind, but rethinking about it, this might be negligible if there is one at all. So, if ____cacheline_aligned is the more sane approach I'll resend a patch using it. Alexander -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
