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0ba5f66836
linux/drivers/tty/serial
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Paul Walmsley 0ba5f66836 tty: serial: OMAP: use a 1-byte RX FIFO threshold in PIO mode 
In the (default) PIO mode, use a one-byte RX FIFO threshold.  The OMAP
UART IP blocks do not appear to be capable of waking the system under
an RX timeout condition.  Since the previous RX FIFO threshold was 16
bytes, this meant that omap-serial.c did not become aware of any
received data until all those bytes arrived or until another UART
interrupt occurred.  This made the serial console and presumably other
serial applications (GPS, serial Bluetooth) unusable or extremely
slow.  A 1-byte RX FIFO threshold also allows the MPU to enter a
low-power consumption state while waiting for the FIFO to fill.

This can be verified using the serial console by comparing the
behavior when "0123456789abcde" is pasted in from another window, with
the behavior when "0123456789abcdef" is pasted in.  Since the former
string is less than sixteen bytes long, the string is not echoed for
some time, while the latter string is echoed immediately.

DMA operation is unaffected by this patch.

Thanks to Russell King - ARM Linux <linux@arm.linux.org.uk> for some
additional information on the standard behavior of the RX timeout
event, which was used to improve this commit description.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Govindraj Raja <govindraj.r@ti.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Russell King <linux@arm.linux.org.uk>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-02-09 10:48:32 -08:00
..
8250 m32r: relocate drivers back out of 8250 dir 2012-02-08 15:04:32 -08:00
cpm_uart TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
jsm jsm: Fixed EEH recovery error 2012-01-24 12:55:36 -08:00
21285.c tty: remove invalid location line in file header 2011-04-19 16:33:36 -07:00
68328serial.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
68328serial.h TTY: serial, remove dead code from 68328 2011-09-22 15:47:54 -07:00
altera_jtaguart.c Merge branch 'devicetree/next' of git://git.secretlab.ca/git/linux-2.6 2011-10-27 08:35:41 +02:00
altera_uart.c Merge branch 'devicetree/next' of git://git.secretlab.ca/git/linux-2.6 2011-10-27 08:35:41 +02:00
amba-pl010.c serial: pl010: Enable module alias autogeneration for AMBA drivers 2011-11-22 10:58:32 +00:00
amba-pl011.c serial: amba-pl011: lock console writes against interrupts 2012-01-24 16:09:55 -08:00
apbuart.c apbuart: fix section mismatch warning 2011-12-27 16:33:13 -05:00
apbuart.h
ar933x_uart.c SERIAL: AR933X: Add driver for the built-in UART of the SoC 2011-12-07 22:02:46 +00:00
atmel_serial.c atmel_serial: fix spinlock lockup in RS485 code 2012-01-04 16:19:34 -08:00
bcm63xx_uart.c serial: bcm63xx_uart: fix irq storm after rx fifo overrun. 2011-06-16 12:01:58 -07:00
bfin_sport_uart.c serial: bfin-sport-uart: Add tty ASYNC_CTS_FLOW flag to do CTS flow control. 2011-12-09 19:05:33 -08:00
bfin_sport_uart.h tty: bfin-sport-uart: Rx interrupt is not called always with irq disabled. 2011-12-09 19:05:33 -08:00
bfin_uart.c serial: bfin-uart: Remove ASYNC_CTS_FLOW flag for hardware automatic CTS. 2011-12-13 09:50:15 -08:00
clps711x.c tty: remove invalid location line in file header 2011-04-19 16:33:36 -07:00
crisv10.c RS485: fix inconsistencies in the meaning of some variables 2011-11-15 12:13:44 -08:00
crisv10.h
dz.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
dz.h
icom.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
icom.h
ifx6x60.c TTY: Remove redundant spi driver bus initialization 2011-11-26 20:19:21 -08:00
ifx6x60.h
imx.c tty: serial: imx: move del_timer_sync() to avoid potential deadlock 2012-01-04 16:30:36 -08:00
ioc3_serial.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
ioc4_serial.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
ip22zilog.c Fix common misspellings 2011-03-31 11:26:23 -03:00
ip22zilog.h
Kconfig serial: Kill off Moorestown code 2012-01-26 11:19:46 -08:00
kgdboc.c tty: Add module.h to drivers/tty users who just expect it there. 2011-10-31 19:31:27 -04:00
lantiq.c Merge branch 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty 2011-10-26 15:11:09 +02:00
m32r_sio_reg.h m32r: relocate drivers back out of 8250 dir 2012-02-08 15:04:32 -08:00
m32r_sio.c m32r: relocate drivers back out of 8250 dir 2012-02-08 15:04:32 -08:00
m32r_sio.h m32r: relocate drivers back out of 8250 dir 2012-02-08 15:04:32 -08:00
Makefile serial: Kill off Moorestown code 2012-01-26 11:19:46 -08:00
max3100.c TTY: Remove redundant spi driver bus initialization 2011-11-26 20:19:21 -08:00
max3107.c TTY: Remove redundant spi driver bus initialization 2011-11-26 20:19:21 -08:00
max3107.h Fix common misspellings 2011-03-31 11:26:23 -03:00
mcf.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
mfd.c Merge 3.2-rc3 into tty-next to handle merge conflict in tty_ldisc.c 2011-11-26 20:07:25 -08:00
mpc52xx_uart.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
mpsc.c
mrst_max3110.c TTY: Remove redundant spi driver bus initialization 2011-11-26 20:19:21 -08:00
mrst_max3110.h max3110: add sysrq support 2011-08-26 11:01:15 -07:00
msm_serial_hs.c msm_serial_hs: Fix spinlock recursion in handling CTS 2011-12-09 19:10:04 -08:00
msm_serial.c Merge branch 'next/dt' of git://git.linaro.org/people/arnd/arm-soc 2011-11-01 21:02:35 -07:00
msm_serial.h tty: remove invalid location line in file header 2011-04-19 16:33:36 -07:00
msm_smd_tty.c tty: remove invalid location line in file header 2011-04-19 16:33:36 -07:00
mux.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
mxs-auart.c clock management changes for i.MX 2012-01-09 14:44:15 -08:00
netx-serial.c tty: remove invalid location line in file header 2011-04-19 16:33:36 -07:00
nwpserial.c tty: Add export.h for EXPORT_SYMBOL/THIS_MODULE to exporters 2011-10-31 19:31:28 -04:00
of_serial.c drivercore: Add helper macro for platform_driver boilerplate 2011-10-25 00:35:47 +02:00
omap-serial.c tty: serial: OMAP: use a 1-byte RX FIFO threshold in PIO mode 2012-02-09 10:48:32 -08:00
pch_uart.c Merge branch 'next' of git://git.infradead.org/users/vkoul/slave-dma 2012-01-17 18:40:24 -08:00
pmac_zilog.c tty/serial/pmac_zilog: Fix suspend & resume 2011-12-16 11:10:01 +11:00
pmac_zilog.h tty/serial/pmac_zilog: Fix suspend & resume 2011-12-16 11:10:01 +11:00
pnx8xxx_uart.c
pxa.c serial: pxa: work around for errata #20 2011-09-22 15:47:53 -07:00
sa1100.c tty: remove invalid location line in file header 2011-04-19 16:33:36 -07:00
samsung.c serial: samsung: Add support for EXYNOS5250 2012-02-02 16:11:24 -08:00
samsung.h serial: samsung: merge probe() function from all SoC specific extensions 2011-12-23 10:07:00 +09:00
sb1250-duart.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
sc26xx.c TTY: serial: convert drivers/tty/serial/* to use module_platform_driver() 2011-11-30 20:11:46 +09:00
serial_core.c serial: Fix wakeup init logic to speed up startup 2012-01-24 16:29:40 -08:00
serial_ks8695.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
serial_txx9.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
sh-sci.c Merge branch 'next' of git://git.infradead.org/users/vkoul/slave-dma 2012-01-17 18:40:24 -08:00
sh-sci.h ARM: mach-shmobile: R-Mobile A1 support. 2011-11-11 16:55:31 +09:00
sirfsoc_uart.c UART: add CSR SiRFprimaII SoC on-chip uart drivers 2011-11-17 11:46:04 -08:00
sirfsoc_uart.h UART: add CSR SiRFprimaII SoC on-chip uart drivers 2011-11-17 11:46:04 -08:00
sn_console.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
suncore.c
suncore.h
sunhv.c
sunsab.c
sunsab.h
sunsu.c treewide: Convert uses of struct resource to resource_size(ptr) 2011-06-10 14:55:36 +02:00
sunzilog.c Fix common misspellings 2011-03-31 11:26:23 -03:00
sunzilog.h
timbuart.c TTY: serial: convert drivers/tty/serial/* to use module_platform_driver() 2011-11-30 20:11:46 +09:00
timbuart.h
uartlite.c Merge branch 'devicetree/next' of git://git.secretlab.ca/git/linux-2.6 2011-10-27 08:35:41 +02:00
ucc_uart.c drivers/serial/ucc_uart.c: Add missing call to init UCC UART port timeout 2011-11-24 02:23:45 -06:00
vr41xx_siu.c TTY: serial: convert drivers/tty/serial/* to use module_platform_driver() 2011-11-30 20:11:46 +09:00
vt8500_serial.c treewide: Convert uses of struct resource to resource_size(ptr) 2011-06-10 14:55:36 +02:00
xilinx_uartps.c tty: Add module.h to drivers/tty users who just expect it there. 2011-10-31 19:31:27 -04:00
zs.c TTY: serial, fix includes in some drivers 2011-09-22 15:49:26 -07:00
zs.h