On 03/10/2015 02:35 PM, smith.winston....@gmail.com wrote:
> On Monday, March 9, 2015 at 1:22:09 PM UTC-4, RobertCNelson wrote:
>
> I've been seeing that locally too, but i see the issue...
>
> CONFIG_SERIAL_8250_NR_UARTS=4
> CONFIG_SERIAL_8250_RUNTIME_UARTS=4
>
>
> One other thing I noticed, I see entries in dmesg output like this:
>
> |
> [ 2.656184]bone-pinmux-helper P8_37_pinmux.28:Setinitial pinmux mode to uart
> [ 2.656791]bone-pinmux-helper P8_38_pinmux.29:Setinitial pinmux mode to uart
> |
>
> In fact, I see it for the ttyO1, ttyO2, ttyO4 and ttyO5 TXD and RXD pins.
> However, I want to enable hardware flow control (CTS/RTS) for ttyO4 and
> ttyO5, so I have added the following lines to my custom .dts file:
>
> |
> P8_33_pinmux {
> mode ="uart";
> };
> P8_35_pinmux {
> mode ="uart";
> };
>
>
> P8_31_pinmux {
> mode ="uart";
> };
> P8_32_pinmux {
> mode ="uart";
> };
>
> |
>
>
> But I don't see corresponding entries in `dmsg` showing the
> bone-pinmux-helper settings the uart modes for 3 of these extra pins (it did
> actually set the uart mode for P8_31). A bit of digging in
> am335x-bone-common-pinmux.dtsi shows that it's missing the pinctrl modes for
> P8_32, P8_33 and P8_35, along with the uart pinmux definitions for P8_33 and
> P8_35. So I added them and I now see bone-pinmux-helper property configuring
> these pins. Here's the diff for am335x-bone-common-pinmux.dtsi:
>
> Next up, I need to get or build a kernel with 5 serial ports enabled to test
> this.
The pinctrl values I use for P8_33 and P8_35 are:
0xd0 0x36 /* P8_35, uart4_ctsn - in | pullup | mode 6 */
0xd4 0x1e /* P8_33, uart4_rtsn - out | pull dis | mode 6 */
(similarly for uart5 pins P8_31 and P8_32)
CTS is active low, so you want the pin to pullup when not driven. Otherwise,
the remote sees CTS enabled when you don't have the port open, and will not
stop sending.
RTS is active low as well, so you either want the pullup/down disabled or
pulled up.
Regards,
Peter Hurley
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