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Add tunable RX interrupt trigger I/F of FIFO buffers.
Serial devices are used as not only message communication devices but control
or sending communication devices. For the latter uses, normally small data
will be exchanged, so user applications want to receive data unit as soon as
possible for real-time tendency. If we have a sensor which sends a 1 byte data
each time and must control a device based on the sensor feedback, the RX
interrupt should be triggered for each data.
According to HW specification of serial UART devices, RX interrupt trigger
can be changed, but the trigger is hard-coded. For example, RX interrupt trigger
in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets
the trigger to only 8bytes.
This patch makes some devices change RX interrupt trigger from userland.
<How to use>
- Read current setting
# cat /sys/class/tty/ttyS0/rx_trig_bytes
8
- Write user setting
# echo 1 > /sys/class/tty/ttyS0/rx_trig_bytes
# cat /sys/class/tty/ttyS0/rx_trig_bytes
1
<Support uart devices>
- 16550A and Tegra (1, 4, 8, or 14 bytes)
- 16650V2 (8, 16, 24, or 28 bytes)
- 16654 (8, 16, 56, or 60 bytes)
- 16750 (1, 16, 32, or 56 bytes)
<Change log>
Changes in V9:
- Use attr_group instead of dev_spec_attr_group of uart_port structure
Changes in V8:
- Divide this patch from V7's patch based on Greg's comment
Changes in V7:
- Add Documentation
- Change I/F name from rx_int_trig to rx_trig_bytes because the name
rx_int_trig is hard to understand how users specify the value
Changes in V6:
- Move FCR_RX_TRIG_* definition in 8250.h to include/uapi/linux/serial_reg.h,
rename those to UART_FCR_R_TRIG_*, and use UART_FCR_TRIGGER_MASK to
UART_FCR_R_TRIG_BITS()
- Change following function names:
convert_fcr2val() => fcr_get_rxtrig_bytes()
convert_val2rxtrig() => bytes_to_fcr_rxtrig()
- Fix typo in serial8250_do_set_termios()
- Delete the verbose error message pr_info() in bytes_to_fcr_rxtrig()
- Rename *rx_int_trig/rx_trig* to *rxtrig* for several functions or variables
(but UI remains rx_int_trig)
- Change the meaningless variable name 'val' to 'bytes' following functions:
fcr_get_rxtrig_bytes(), bytes_to_fcr_rxtrig(), do_set_rxtrig(),
do_serial8250_set_rxtrig(), and serial8250_set_attr_rxtrig()
- Use up->fcr in order to get rxtrig_bytes instead of rx_trig_raw in
fcr_get_rxtrig_bytes()
- Use conf_type->rxtrig_bytes[0] instead of switch statement for support check
in register_dev_spec_attr_grp()
- Delete the checking whether a user changed FCR or not when minimum buffer
is needed in serial8250_do_set_termios()
Changes in V5.1:
- Fix FCR_RX_TRIG_MAX_STATE definition
Changes in V5:
- Support Tegra, 16650V2, 16654, and 16750
- Store default FCR value to up->fcr when the port is first created
- Add rx_trig_byte[] in uart_config[] for each device and use rx_trig_byte[]
in convert_fcr2val() and convert_val2rxtrig()
Changes in V4:
- Introduce fifo_bug flag in uart_8250_port structure
This is enabled only when parity is enabled and UART_BUG_PARITY is enabled
for up->bugs. If this flag is enabled, user cannot set RX trigger.
- Return -EOPNOTSUPP when it does not support device at convert_fcr2val() and
at convert_val2rxtrig()
- Set the nearest lower RX trigger when users input a meaningless value at
convert_val2rxtrig()
- Check whether p->fcr is existing at serial8250_clear_and_reinit_fifos()
- Set fcr = up->fcr in the begging of serial8250_do_set_termios()
Changes in V3:
- Change I/F from ioctl(2) to sysfs(rx_int_trig)
Changed in V2:
- Use _IOW for TIOCSFIFORTRIG definition
- Pass the interrupt trigger value itself
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
157 lines
4.7 KiB
Plaintext
157 lines
4.7 KiB
Plaintext
What: /sys/class/tty/console/active
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Date: Nov 2010
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Contact: Kay Sievers <kay.sievers@vrfy.org>
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Description:
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Shows the list of currently configured
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console devices, like 'tty1 ttyS0'.
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The last entry in the file is the active
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device connected to /dev/console.
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The file supports poll() to detect virtual
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console switches.
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What: /sys/class/tty/tty0/active
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Date: Nov 2010
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Contact: Kay Sievers <kay.sievers@vrfy.org>
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Description:
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Shows the currently active virtual console
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device, like 'tty1'.
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The file supports poll() to detect virtual
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console switches.
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What: /sys/class/tty/ttyS0/uartclk
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Date: Sep 2012
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Contact: Tomas Hlavacek <tmshlvck@gmail.com>
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Description:
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Shows the current uartclk value associated with the
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UART port in serial_core, that is bound to TTY like ttyS0.
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uartclk = 16 * baud_base
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/type
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Shows the current tty type for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/line
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Shows the current tty line number for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/port
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Shows the current tty port I/O address for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/irq
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Shows the current primary interrupt for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/flags
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the tty port status flags for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/xmit_fifo_size
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the transmit FIFO size for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/close_delay
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the closing delay time for this port in ms.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/closing_wait
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the close wait time for this port in ms.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/custom_divisor
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the custom divisor if any that is set on this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/io_type
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the I/O type that is to be used with the iomem base
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address.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/iomem_base
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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The I/O memory base for this port.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/iomem_reg_shift
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Date: October 2012
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Contact: Alan Cox <alan@linux.intel.com>
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Description:
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Show the register shift indicating the spacing to be used
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for accesses on this iomem address.
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These sysfs values expose the TIOCGSERIAL interface via
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sysfs rather than via ioctls.
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What: /sys/class/tty/ttyS0/rx_trig_bytes
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Date: May 2014
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Contact: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
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Description:
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Shows current RX interrupt trigger bytes or sets the
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user specified value to change it for the FIFO buffer.
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Users can show or set this value regardless of opening the
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serial device file or not.
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The RX trigger can be set one of four kinds of values for UART
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serials. When users input a meaning less value to this I/F,
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the RX trigger is changed to the nearest lower value for the
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device specification. For example, when user sets 7bytes on
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16550A, which has 1/4/8/14 bytes trigger, the RX trigger is
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automatically changed to 4 bytes.
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