Changes between Version 32 and Version 33 of serial


Ignore:
Timestamp:
07/12/2023 09:42:10 PM (17 months ago)
Author:
Ryan Erbstoesser
Comment:

add warning for venice shared serial console. add note that venice uses device tree and not iocs

Legend:

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  • serial

    v32 v33  
    136136
    137137
    138 [=#console]
    139 == serial Console
    140 There are times when one may not care about serial Linux console because the serial port is desired for other uses.
    141 
    142 See [wiki:silenceconsole silenceconsole] for details on silencing or changing the serial console for boot firmware, Linux kernel, and OS.
    143138
    144139
    … …  
    295290=== Venice
    296291
    297 Software must enable RS485 at boot via device-tree or use the TIOCSRS485 ioctl to configure TXEN - see [#TIOCSRS485 below]).
     292Software must enable RS485 at boot via device-tree.
    298293
    299294See [#venice below]
    … …  
    354349Code Examples:
    355350 * ANSI-C:
     351 * '''Note the below code is not required for Venice, as it is handled in the device tree'''
    356352{{{#!c
    357353        #include <linux/serial.h>
    … …  
    415411 - https://www.kernel.org/doc/Documentation/serial/serial-rs485.txt
    416412 - https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/rs485.yaml
     413
     414
     415
     416
     417
     418
     419[=#notes]
     420== Specific Product / Model Notes
     421
     422
     423[=#venice]
     424=== Venice
     425Most Venice products have a flexible [http://dev.gateworks.com/datasheets/sp335e.pdf MaxLinear SP335E] RS-232/RS-485/RS-422 transceiver which is software configurable. For these boards a device-tree fragment is used to configure the kernel appropriately for the mode you desire:
     426 * 2x RS232 TX/RX (default configuration requiring no dt overlay)
     427 * 1x RS232 TX/RX/RTS/CTS (uses rs232-rts dt overlay)
     428 * 1x RS485 (half duplex) (uses rs485 dt overlay)
     429 * 1x RS422 (full duplex) (uses rs422 dt overlay)
     430
     431''' WARNING ''' Some Venice models such as the GW73xx have the default Linux serial console being output to the same UART that a RS485 might be using. Thus, it is critical to disable the Linux serial console with the console variable in u-boot. Please note that when doing this, it is critical to first enable something like ssh to access the board over the network.
     432 * Enable ssh first [wiki:ubuntu#SSHServer Instructions for Ubuntu]
     433 * Disable serial console in uboot prompt or move to a different port:
     434  *
     435{{{
     436setenv console 'console=/dev/null'
     437saveenv
     438}}}
     439   * Also see [wiki:silenceconsole silenceconsole] for details on silencing or changing the serial console for boot firmware, Linux kernel, and OS.
     440
     441To use dt overlays you specify the appropriate overlay(s) in the U-Boot {{{fdt_overlays}}} environment variable in the U-Boot bootloader. This instructs U-Boot to load and apply those dt overlay fragments to the board dt before booting Linux. Note that you can have more than one dt overlay specified in the {{{fdt_overlays}}} separated by a space:
     442 * imx8mm-venice-gw730x-0x RS485:
     443{{{#!bash
     444setenv fdt_overlays "$fdt_overlays imx8mm-venice-gw73xx-0x-rs485.dtbo"
     445saveenv
     446}}}
     447 * imx8mm-venice-gw730x-0x RS422:
     448{{{#!bash
     449setenv fdt_overlays "imx8mm-venice-gw73xx-0x-rs422.dtbo"
     450saveenv
     451}}}
     452 * imx8mm-venice-gw730x-0x RS232-CTSRTS flow control:
     453{{{#!bash
     454setenv fdt_overlays "imx8mm-venice-gw73xx-0x-rs232-rts.dtbo"
     455saveenv
     456}}}
     457 * imx8mm-venice-gw730x-0x default 2x RS232 TX/RX:
     458{{{#!bash
     459setenv fdt_overlays
     460saveenv
     461}}}
     462
     463For Venice when configured for RS485 or RS422 you do not need to use the TIOCSRS485 as the dt fragments will enable this on bootup as well as configure the UARTs transmit enable pin.
     464
     465If you wish to enable the SP335E on-board RS485 termination (which is disabled by default) you can set the GPIO manually:
     466 * GW730x/GW720x:
     467  - U-Boot:
     468{{{#!bash
     469u-boot=> gpio status GPIO1_0
     470Bank GPIO1_:
     471GPIO1_0: output: 0 [x] rs485_term.gpio-hog
     472u-boot=> gpio set GPIO1_0
     473gpio: pin GPIO1_0 (gpio 0) value is 1
     474}}}
     475  - Linux (sysfs) (deprecated API)
     476{{{#!bash
     477root@focal-venice:~# grep rs485_term /sys/kernel/debug/gpio
     478 gpio-0   (rs485_term          )
     479root@focal-venice:~# echo 0 > /sys/class/gpio/export
     480root@focal-venice:~# echo out > /sys/class/gpio/gpio0/direction
     481root@focal-venice:~# echo 1 > /sys/class/gpio/gpio0/value
     482}}}
     483  - Linux (gpiolib)
     484{{{#!bash
     485root@focal-venice:~# gpiofind "rs485_term"
     486gpiochip0 0
     487root@focal-venice:~# gpioset --mode=signal --background gpiochip0 0=1
     488}}}
     489   * Note we have to tell {{{gpioset}}} to remaining running until it receives a signal in order to keep the GPIO line from reverting back to its original state when the process exits. If you use the deprecated {{{sysfs}}} API or set it in U-Boot it may be easier
     490
     491Note that if you want to be able to change the UART mode at runtime instead of at boot time you can use the 'rs232-rts' overlay which adds the RTS signal capability to the UART, configure the various gpios manually at runtime via sysfs or gpiod, and use the TIOCSRS485 ioctl to invoke RS485 mode with the polarity of the RTS pin handled by setting rs485conf.flags SER_RS485_RTS_AFTER_SEND
     492
     493[=#newport]
     494=== Newport
     495Most Newport products have a flexible [http://dev.gateworks.com/datasheets/sp335e.pdf MaxLinear SP335E] RS-232/RS-485/RS-422 transceiver which is software configurable. For these boards the Bootloader {{{hwconfig}}} environment variable can be used to configure the functionality of the serial ports at power-up between dual RS232 without flow control (default), single RS232 with hardware flow control, and RS485 (full/half duplex and optional termination). See [wiki:/newport/bootloader#hwconfig:serialConfiguration Newport bootloader hwconfig] for more details.
     496
     497If you wish to configure the SP335E transceiver yourself you can control it at runtime through the following GPIO's (which is what the Boot firmware will do for you via the {{{hwconfig}}} variable):
     498 * GPIO21: UART_HALF - selects full (low) or half (high) duplex (RS485 mode only)
     499 * GPIO22: UART_TERM - disables (low) or enables (high) on-chip termination (RS485 mode only)
     500 * GPIO23: UART_RS485 - selects between RS232 (low) and RS245 (high) modes
     501
     502See [wiki:gpio gpio] for details on using GPIO from Linux userspace or use the U-Boot bootloader {{{gpio}}} command.
     503
     504The CN80XX / CN81XX has 4 TTL level UARTs with the following mapping:
     505||= UART =||= device-tree alias =||= Linux device =||
     506|| UART0 || serial0 || /dev/ttyAMA0 ||
     507|| UART1 || serial1 || /dev/ttyAMA1 ||
     508|| UART2 || serial2 || /dev/ttyAMA2 ||
     509|| UART3 || serial3 || /dev/ttyAMA3 ||
     510
     511The Linux kernel uses the {{{console}}} parameter from the Kernel cmdline to specify the serial console. You can usually modify the 'console' U-boot env variable if you want to change the default console UART as it typically gets passed on to the kernel:
     512{{{
     513Newport > setenv console '/dev/ttyAMA2,115200n8'; saveenv
     514}}}
     515 * Specify that Linux and userspace use UART2
     516
     517The U-Boot Bootloader (as well as kernel if the {{{console}}} cmdline is not specified) uses the device-tree 'chosen' node 'stdout-path' property to specify serial console. For example the default is specified in the cn81xx-linux.dtsi:
     518{{{
     519        chosen {
     520               stdout-path = "serial0:115200n8";
     521        };
     522}}}
     523
     524If you wish to change the serial console in the BDK or ATF, you will need to modify the source code which will take some digging.
    417525
    418526
    … …  
    594702}}}
    595703
    596 
    597 
    598 [=#notes]
    599 == Specific Product / Model Notes
    600 
    601 
    602 [=#venice]
    603 === Venice
    604 Most Venice products have a flexible [http://dev.gateworks.com/datasheets/sp335e.pdf MaxLinear SP335E] RS-232/RS-485/RS-422 transceiver which is software configurable. For these boards a device-tree frament is used to configure the kernel appropriately for the mode you desire:
    605  * 2x RS232 TX/RX (default configuration requiring no dt overlay)
    606  * 1x RS232 TX/RX/RTS/CTS (uses rs232-rts dt overlay)
    607  * 1x RS485 (half duplex) (uses rs485 dt overlay)
    608  * 1x RS422 (full duplex) (uses rs422 dt overlay)
    609 
    610 To use dt overlays you specify the appropriate overlay(s) in the U-Boot {{{fdt_overlays}}} environment variable in the U-Boot bootloader. This instructs U-Boot to load and apply those dt overlay fragments to the board dt before booting Linux. Note that you can have more than one dt overlay specified in the {{{fdt_overlays}}} separated by a space:
    611  * imx8mm-venice-gw730x-0x RS485:
    612 {{{#!bash
    613 setenv fdt_overlays "$fdt_overlays imx8mm-venice-gw73xx-0x-rs485.dtbo"
    614 saveenv
    615 }}}
    616  * imx8mm-venice-gw730x-0x RS422:
    617 {{{#!bash
    618 setenv fdt_overlays "imx8mm-venice-gw73xx-0x-rs422.dtbo"
    619 saveenv
    620 }}}
    621  * imx8mm-venice-gw730x-0x RS232-CTSRTS flow control:
    622 {{{#!bash
    623 setenv fdt_overlays "imx8mm-venice-gw73xx-0x-rs232-rts.dtbo"
    624 saveenv
    625 }}}
    626  * imx8mm-venice-gw730x-0x default 2x RS232 TX/RX:
    627 {{{#!bash
    628 setenv fdt_overlays
    629 saveenv
    630 }}}
    631 
    632 For Venice when configured for RS485 or RS422 you do not need to use the TIOCSRS485 as the dt fragments will enable this on bootup as well as configure the UARTs transmit enable pin.
    633 
    634 If you wish to enable the SP335E on-board RS485 termination (which is disabled by default) you can set the GPIO manually:
    635  * GW730x/GW720x:
    636   - U-Boot:
    637 {{{#!bash
    638 u-boot=> gpio status GPIO1_0
    639 Bank GPIO1_:
    640 GPIO1_0: output: 0 [x] rs485_term.gpio-hog
    641 u-boot=> gpio set GPIO1_0
    642 gpio: pin GPIO1_0 (gpio 0) value is 1
    643 }}}
    644   - Linux (sysfs) (deprecated API)
    645 {{{#!bash
    646 root@focal-venice:~# grep rs485_term /sys/kernel/debug/gpio
    647  gpio-0   (rs485_term          )
    648 root@focal-venice:~# echo 0 > /sys/class/gpio/export
    649 root@focal-venice:~# echo out > /sys/class/gpio/gpio0/direction
    650 root@focal-venice:~# echo 1 > /sys/class/gpio/gpio0/value
    651 }}}
    652   - Linux (gpiolib)
    653 {{{#!bash
    654 root@focal-venice:~# gpiofind "rs485_term"
    655 gpiochip0 0
    656 root@focal-venice:~# gpioset --mode=signal --background gpiochip0 0=1
    657 }}}
    658    * Note we have to tell {{{gpioset}}} to remaining running until it receives a signal in order to keep the GPIO line from reverting back to its original state when the process exits. If you use the deprecated {{{sysfs}}} API or set it in U-Boot it may be easier
    659 
    660 Note that if you want to be able to change the UART mode at runtime instead of at boot time you can use the 'rs232-rts' overlay which adds the RTS signal capability to the UART, configure the various gpios manually at runtime via sysfs or gpiod, and use the TIOCSRS485 ioctl to invoke RS485 mode with the polarity of the RTS pin handled by setting rs485conf.flags SER_RS485_RTS_AFTER_SEND
    661 
    662 [=#newport]
    663 === Newport
    664 Most Newport products have a flexible [http://dev.gateworks.com/datasheets/sp335e.pdf MaxLinear SP335E] RS-232/RS-485/RS-422 transceiver which is software configurable. For these boards the Bootloader {{{hwconfig}}} environment variable can be used to configure the functionality of the serial ports at power-up between dual RS232 without flow control (default), single RS232 with hardware flow control, and RS485 (full/half duplex and optional termination). See [wiki:/newport/bootloader#hwconfig:serialConfiguration Newport bootloader hwconfig] for more details.
    665 
    666 If you wish to configure the SP335E transceiver yourself you can control it at runtime through the following GPIO's (which is what the Boot firmware will do for you via the {{{hwconfig}}} variable):
    667  * GPIO21: UART_HALF - selects full (low) or half (high) duplex (RS485 mode only)
    668  * GPIO22: UART_TERM - disables (low) or enables (high) on-chip termination (RS485 mode only)
    669  * GPIO23: UART_RS485 - selects between RS232 (low) and RS245 (high) modes
    670 
    671 See [wiki:gpio gpio] for details on using GPIO from Linux userspace or use the U-Boot bootloader {{{gpio}}} command.
    672 
    673 The CN80XX / CN81XX has 4 TTL level UARTs with the following mapping:
    674 ||= UART =||= device-tree alias =||= Linux device =||
    675 || UART0 || serial0 || /dev/ttyAMA0 ||
    676 || UART1 || serial1 || /dev/ttyAMA1 ||
    677 || UART2 || serial2 || /dev/ttyAMA2 ||
    678 || UART3 || serial3 || /dev/ttyAMA3 ||
    679 
    680 The Linux kernel uses the {{{console}}} parameter from the Kernel cmdline to specify the serial console. You can usually modify the 'console' U-boot env variable if you want to change the default console UART as it typically gets passed on to the kernel:
    681 {{{
    682 Newport > setenv console '/dev/ttyAMA2,115200n8'; saveenv
    683 }}}
    684  * Specify that Linux and userspace use UART2
    685 
    686 The U-Boot Bootloader (as well as kernel if the {{{console}}} cmdline is not specified) uses the device-tree 'chosen' node 'stdout-path' property to specify serial console. For example the default is specified in the cn81xx-linux.dtsi:
    687 {{{
    688         chosen {
    689                stdout-path = "serial0:115200n8";
    690         };
    691 }}}
    692 
    693 If you wish to change the serial console in the BDK or ATF, you will need to modify the source code which will take some digging.
    694 
    695 
    696 
    697 
    698704[=#console]
    699705= Serial Console
     706
     707
     708[=#console]
     709== serial Console
     710There are times when one may not care about serial Linux console because the serial port is desired for other uses.
     711
     712See [wiki:silenceconsole silenceconsole] for details on silencing or changing the serial console for boot firmware, Linux kernel, and OS.
    700713
    701714== Serial Console Window Size