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d7aff291d0
linux/drivers/tty/serial
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Maciej W. Rozycki d7aff291d0 serial: 8250: Define RX trigger levels for OxSemi 950 devices 
Oxford Semiconductor 950 serial port devices have a 128-byte FIFO and in
the enhanced (650) mode, which we select in `autoconfig_has_efr' with
the ECB bit set in the EFR register, they support the receive interrupt
trigger level selectable with FCR bits 7:6 from the set of 16, 32, 112,
120.  This applies to the original OX16C950 discrete UART[1] as well as
950 cores embedded into more complex devices.

For these devices we set the default to 112, which sets an excessively
high level of 112 or 7/8 of the FIFO capacity, unlike with other port
types where we choose at most 1/2 of their respective FIFO capacities.
Additionally we don't make the trigger level configurable.  Consequently
frequent input overruns happen with high bit rates where hardware flow
control cannot be used (e.g. terminal applications) even with otherwise
highly-performant systems.

Lower the default receive interrupt trigger level to 32 then, and make
it configurable.  Document the trigger levels along with other port
types, including the set of 16, 32, 64, 112 for the transmit interrupt
as well[2].

References:

[1] "OX16C950 rev B High Performance UART with 128 byte FIFOs", Oxford
    Semiconductor, Inc., DS-0031, Sep 05, Table 10: "Receiver Trigger
    Levels", p. 22

[2] same, Table 9: "Transmit Interrupt Trigger Levels", p. 22

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2106260608480.37803@angie.orcam.me.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-27 12:05:46 +02:00
..
8250 serial: 8250: Define RX trigger levels for OxSemi 950 devices 2021-07-27 12:05:46 +02:00
cpm_uart tty: make use of tty_get_{char,frame}_size 2021-06-15 14:03:27 +02:00
jsm tty: serial: jsm: hold port lock when reporting modem line changes 2021-07-21 12:36:48 +02:00
21285.c tty: serial: 21285: fix lockup on open 2020-10-28 13:39:14 +01:00
altera_jtaguart.c serial: altera_jtaguart: drop low-latency workaround 2021-04-22 12:09:24 +02:00
altera_uart.c serial: altera_uart: drop low-latency workaround 2021-04-22 12:09:24 +02:00
amba-pl010.c serial: amba-pl010: drop low-latency workaround 2021-04-22 12:09:24 +02:00
amba-pl011.c arm pl011 serial: support multi-irq request 2021-07-21 12:39:47 +02:00
amba-pl011.h
apbuart.c serial: apbuart: drop low-latency workaround 2021-04-22 12:09:25 +02:00
apbuart.h
ar933x_uart.c serial: ar933x: drop low-latency workaround 2021-04-22 12:09:25 +02:00
arc_uart.c tty: cumulate and document tty_struct::flow* members 2021-05-13 16:57:16 +02:00
atmel_serial.c tty: serial: atmel: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:11 +02:00
atmel_serial.h tty: serial: Use the correct style for SPDX License Identifier 2020-03-07 09:52:01 +01:00
bcm63xx_uart.c serial: bcm63xx: drop low-latency workaround 2021-04-22 12:09:25 +02:00
clps711x.c tty/serial: Migrate clps711x to use has_sysrq 2019-12-18 15:04:46 +01:00
digicolor-usart.c
dz.c tty: serial: dz: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:11 +02:00
dz.h
earlycon-arm-semihost.c
earlycon-riscv-sbi.c
earlycon.c earlycon: simplify earlycon-table implementation 2020-12-04 15:49:48 +01:00
fsl_linflexuart.c tty: serial: linflexuart: Remove unnecessary '|' operation and add error count 2020-11-06 17:12:30 +01:00
fsl_lpuart.c serial: fsl_lpuart: disable DMA for console and fix sysrq 2021-05-13 16:08:26 +02:00
icom.c tty: serial: icom: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:11 +02:00
icom.h tty: serial: Use the correct style for SPDX License Identifier 2020-03-07 09:52:01 +01:00
imx_earlycon.c tty: serial: imx: add imx earlycon driver 2020-07-29 17:11:02 +02:00
imx.c serial: imx: Add DMA buffer configuration via DT 2021-06-04 15:11:16 +02:00
ip22zilog.c tty: serial: ip22zilog: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
ip22zilog.h
Kconfig tty: serial: Fix spelling mistake "Asychronous" -> "Asynchronous" 2021-07-21 12:47:33 +02:00
kgdb_nmi.c serial: kgdb_nmi: remove redundant initialization of variable c 2021-05-20 16:22:09 +02:00
kgdboc.c Linux 5.8-rc6 2020-07-20 09:39:11 +02:00
lantiq.c tty/serial/lantiq: convert comma to semicolon 2020-12-28 16:10:50 +01:00
liteuart.c serial: liteuart: Add support for earlycon 2021-05-20 16:35:01 +02:00
lpc32xx_hs.c serial: lpc32xx_hs: drop low-latency workaround 2021-04-22 12:09:25 +02:00
Makefile Revert "tty: serial: Add UART driver for Cortina-Access platform" 2021-06-24 14:46:32 +02:00
max310x.c Merge 5.13-rc4 into tty-next 2021-05-31 09:44:28 +02:00
max3100.c tty_port: drop last traces of low_latency 2021-01-07 16:17:32 +01:00
mcf.c serial: mcf: drop low-latency workaround 2021-04-22 12:09:25 +02:00
men_z135_uart.c tty: serial, fix kernel-doc 2020-08-18 13:51:18 +02:00
meson_uart.c tty: serial: meson: retrieve port FIFO size from DT 2021-05-20 16:11:20 +02:00
milbeaut_usio.c tty/serial: Migrate milbeaut_usio to use has_sysrq 2019-12-18 15:04:51 +01:00
mpc52xx_uart.c serial: mpc52xx_uart: drop low-latency workaround 2021-04-22 12:09:25 +02:00
mps2-uart.c
msm_serial.c serial: msm_serial: drop low-latency workaround 2021-04-22 12:09:25 +02:00
mux.c tty: serial: mux: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
mvebu-uart.c serial: mvebu-uart: remove unused member nb from struct mvebu_uart 2021-06-25 13:53:51 +02:00
mxs-auart.c tty: make use of tty_get_{char,frame}_size 2021-06-15 14:03:27 +02:00
omap-serial.c serial: drop irq-flags initialisations 2021-05-20 16:24:05 +02:00
owl-uart.c serial: owl: drop low-latency workaround 2021-04-22 12:09:25 +02:00
pch_uart.c serial: pch_uart: fix build error with !CONFIG_DEBUG_FS 2021-03-23 10:31:09 +01:00
pic32_uart.c serial: pic32_uart: Use uart_console() helper 2020-03-12 10:00:22 +01:00
pic32_uart.h tty: serial: Use the correct style for SPDX License Identifier 2020-03-07 09:52:01 +01:00
pmac_zilog.c tty: serial: pmac_zilog: include <linux/io.h> insteiad of <asm/io.h> 2021-05-13 18:29:12 +02:00
pmac_zilog.h tty: serial: pmac_zilog: Remove unused disposable variable 'garbage' 2020-11-13 15:28:27 +01:00
pxa.c tty/serial: Migrate pxa to use has_sysrq 2019-12-18 15:04:57 +01:00
qcom_geni_serial.c serial: qcom_geni_serial: use DT aliases according to DT bindings 2021-06-24 14:51:28 +02:00
rda-uart.c serial: rda: drop low-latency workaround 2021-04-22 12:09:26 +02:00
rp2.c serial: rp2: use 'request_firmware' instead of 'request_firmware_nowait' 2021-05-21 20:34:02 +02:00
sa1100.c serial: sa1100: drop low-latency workaround 2021-04-22 12:09:26 +02:00
samsung_tty.c serial: samsung: use dma_ops of DMA if attached 2021-07-21 12:40:33 +02:00
sb1250-duart.c tty: serial: sb1250-duart: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
sc16is7xx.c serial: sc16is7xx: Use devm_clk_get_optional() 2021-05-20 16:30:40 +02:00
sccnxp.c tty/serial: Migrate sccnxp to use has_sysrq 2019-12-18 15:05:00 +01:00
serial_core.c serial: core: Report magic multiplier extra baud rates 2021-07-21 12:35:01 +02:00
serial_mctrl_gpio.c serial: mctrl_gpio: Fix passing zero to 'ERR_PTR' warning 2020-11-06 17:12:05 +01:00
serial_mctrl_gpio.h tty: serial: Use the correct style for SPDX License Identifier 2020-03-07 09:52:01 +01:00
serial_txx9.c tty: serial: txx9: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
serial-tegra.c serial: tegra: Fix a mask operation that is always true 2021-05-13 17:07:43 +02:00
sh-sci.c tty: make use of tty_get_{char,frame}_size 2021-06-15 14:03:27 +02:00
sh-sci.h serial: sh-sci: Add support for RZ/G2L SoC 2021-06-04 15:12:40 +02:00
sifive.c serial: sifive: drop low-latency workaround 2021-04-22 12:09:26 +02:00
sprd_serial.c serial: sprd: remove redundant sprd_port cleanup 2020-03-18 12:20:04 +01:00
st-asc.c tty: serial: st-asc: Demote a kernel-doc formatting abuse 2021-05-20 17:06:17 +02:00
stm32-usart.c tty: make use of tty_get_{char,frame}_size 2021-06-15 14:03:27 +02:00
stm32-usart.h serial: stm32: add FIFO threshold configuration 2021-04-22 12:11:25 +02:00
suncore.c
sunhv.c Revert "serial: sunhv: Initialize lock for non-registered console" 2020-07-21 18:21:49 +02:00
sunsab.c tty: serial: sunsab: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
sunsab.h
sunsu.c tty: serial: sunsu: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
sunzilog.c tty: serial: sunzilog: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
sunzilog.h
tegra-tcu.c serial: tegra-tcu: Reorder channel initialization 2021-06-15 14:02:06 +02:00
timbuart.c serial: timbuart: drop low-latency workaround 2021-04-22 12:09:26 +02:00
timbuart.h tty: serial: Use the correct style for SPDX License Identifier 2020-03-07 09:52:01 +01:00
uartlite.c tty: serial: uartlite: Add runtime pm support 2021-07-21 12:46:52 +02:00
ucc_uart.c firmware: replace HOTPLUG with UEVENT in FW_ACTION defines 2021-05-13 16:14:45 +02:00
vr41xx_siu.c tty: serial: vr41xx_siu: include <linux/io.h> instead of <asm/io.h> 2021-05-13 18:29:12 +02:00
vt8500_serial.c serial: vt8500: drop low-latency workaround 2021-04-22 12:09:26 +02:00
xilinx_uartps.c serial: Prefer unsigned int to bare use of unsigned 2021-06-24 14:51:45 +02:00
zs.c TTY/Serial driver updates for 5.6-rc1 2020-01-29 10:13:27 -08:00
zs.h