Thread (17 messages) 17 messages, 2 authors, 2017-01-11

Re: imx: RS-485 problems during TX, maybe DMA related

From: Fabio Estevam <festevam@gmail.com>
Date: 2017-01-07 14:57:22
Also in: linux-arm-kernel, lkml

Hi Clemens,

On Sat, Jan 7, 2017 at 11:45 AM, Clemens Gruber
[off-list ref] wrote:
It should work like this, I don't think using an extra GPIO is
necessary.
The MX6QDL_PAD_CSI0_DAT16__UART4_CTS_B option is only valid in dte mode.

If I pass 'fsl,dte-mode' then I can see this pin toggling. (rx, tx
would not work as expected).

In the default dce mode I can see UART4_CTS_B pin toggling when I
monitor CSI0_DAT17 pin and configure it as:

MX6QDL_PAD_CSI0_DAT17__UART4_CTS_B

,but unfortunately this pin does not go to the TXEN pin of the RS485
transceiver.

So this means that with the hardware I have access to my only
alternative is to set MX6QDL_PAD_CSI0_DAT16__GPIO6_IO02.
quoted
So I was never able to observe the DE pin toggling correctly.
But did you set SER_RS485_RX_DURING_TX in your flags? This is counter
intuitive, but I observed that it would not work otherwise.
Yes, I have also tried when I read your email, but did not help on my case.

Thanks,

Fabio Estevam
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