Apologies, but my original email bounced for Andy and Heikki, resending.
----
Hi Andy,
I saw that you have discovered that commit ec5a11a91eec ("serial: 8250:
Validate dmaengine rx chan meets requirements") introduced a regression
in the 8250 uart driver. For SoCFPGA platform, I am seeing this error:
[ 5.541751] ttyS0 - failed to request DMA
Reverting the commit ec5a11a91eec removes the error.
I saw that you started the discussion, but I didn't see that a patch was
included[1].
The following patch seems to fix the error, but I'm not sure if it's the
same fix that you had in mind.
Thanks,
Dinh
[1] http://marc.info/?l=linux-serial&m=146254187602862&w=2
---------------8<------------
diff --git a/drivers/tty/serial/8250/8250_dma.c
b/drivers/tty/serial/8250/8250_dma.c
index 7f33d1c..847a203 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -176,7 +176,7 @@ int serial8250_request_dma(struct uart_8250_port *p)
ret = dma_get_slave_caps(dma->rxchan, &caps);
if (ret)
goto release_rx;
- if (!caps.cmd_pause || !caps.cmd_terminate ||
+ if ((!caps.cmd_pause || !caps.cmd_terminate) &&
caps.residue_granularity ==
DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
ret = -EINVAL;
goto release_rx;
