If the DMA engine doesn't support residue processing then the RX DMA handling won't work terribly well if polling is enabled. So, disable RX DMA if residue handling isn't available.
Signed-off-by: Andrew Jackson <[email protected]> --- drivers/tty/serial/amba-pl011.c | 17 ++++++++++++++++- 1 files changed, 16 insertions(+), 1 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 7c5e263..79b9c93 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -322,7 +322,22 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * .src_maxburst = uap->fifosize >> 2, .device_fc = false, }; + struct dma_slave_caps caps; + /* + * Some DMA controllers provide information on their capabilities. + * If the controller does, check for suitable residue processing + * otherwise assime all is well. + */ + if (0 == dma_get_slave_caps(chan, &caps)) { + if (caps.residue_granularity == + DMA_RESIDUE_GRANULARITY_DESCRIPTOR) { + dma_release_channel(chan); + dev_info(uap->port.dev, + "RX DMA disabled - no residue processing\n"); + return; + } + } dmaengine_slave_config(chan, &rx_conf); uap->dmarx.chan = chan; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
