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 <Andrew.Jackson@xxxxxxx>
---
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
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