Commits
Vignesh R committed c687c46e9e4
spi: spi-ti-qspi: Use bounce buffer if read buffer is not DMA'ble Flash filesystems like JFFS2, UBIFS and MTD block layer can provide vmalloc'd or kmap'd buffers that cannot be mapped using dma_map_sg() and can potentially be in memory region above 32bit addressable region(ie buffers belonging to memory region backed by LPAE) of DMA, implement spi_flash_can_dma() interface to inform SPI core not to map such buffers. When buffers are not mapped for DMA, then use a pre allocated bounce buffer(64K = typical flash erase sector size) to read from flash and then do a copy to actual destination buffer. This is approach is much faster than using memcpy using CPU and also reduces CPU load. With this patch, UBIFS read speed is ~18MB/s and CPU utilization <20% on DRA74 Rev H EVM. Performance degradation is negligible when compared with non bounce buffer case while using UBIFS. Signed-off-by: Vignesh R <vigneshr@ti.com> Signed-off-by: Mark Brown <broonie@kernel.org>