diff options
Diffstat (limited to 'Documentation/spi/pxa2xx.rst')
| -rw-r--r-- | Documentation/spi/pxa2xx.rst | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/Documentation/spi/pxa2xx.rst b/Documentation/spi/pxa2xx.rst index 143f1df83f79..19479b801826 100644 --- a/Documentation/spi/pxa2xx.rst +++ b/Documentation/spi/pxa2xx.rst @@ -193,17 +193,14 @@ mode supports both coherent and stream based DMA mappings. The following logic is used to determine the type of I/O to be used on a per "spi_transfer" basis:: - if !enable_dma then - always use PIO transfers + if spi_message.len > 65536 then + if spi_message.is_dma_mapped or rx_dma_buf != 0 or tx_dma_buf != 0 then + reject premapped transfers - if spi_message.len > 8191 then print "rate limited" warning use PIO transfers - if spi_message.is_dma_mapped and rx_dma_buf != 0 and tx_dma_buf != 0 then - use coherent DMA mode - - if rx_buf and tx_buf are aligned on 8 byte boundary then + if enable_dma and the size is in the range [DMA burst size..65536] then use streaming DMA mode otherwise |