linux/drivers/tty
Paul Walmsley 5816269e4e 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>
2012-02-02 13:00:15 -08:00
..
hvc serial: Kill off NO_IRQ 2012-01-26 17:14:50 -08:00
ipwireless Merge git://git.kernel.org/pub/scm/linux/kernel/git/brodo/pcmcia-2.6 2011-05-24 13:28:35 -07:00
serial tty: serial: OMAP: use a 1-byte RX FIFO threshold in PIO mode 2012-02-02 13:00:15 -08:00
vt tty: Fix memory leak in virtual console when enable unicode translation 2012-01-04 16:18:55 -08:00
amiserial.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
bfin_jtag_comm.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
cyclades.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
ehv_bytechan.c drivers/tty: don't use the byte channel handle as a parameter in ehv_bytechan.c 2011-09-26 16:38:43 -07:00
isicom.c TTY: irq: Remove IRQF_DISABLED 2011-09-22 16:08:57 -07:00
Kconfig Merge branch 'for-linus' of git://github.com/richardweinberger/linux 2011-11-02 09:45:39 -07:00
Makefile tty/powerpc: introduce the ePAPR embedded hypervisor byte channel driver 2011-08-23 10:32:56 -07:00
moxa.c drivers/tty: use printk_ratelimited() instead of printk_ratelimit() 2011-07-01 15:35:45 -07:00
moxa.h tty: move a number of tty drivers from drivers/char/ to drivers/tty/ 2011-02-22 16:14:56 -08:00
mxser.c TTY: mxser+cyclades remove wait_until_sent debug code 2011-08-23 10:34:07 -07:00
mxser.h Fix common misspellings 2011-03-31 11:26:23 -03:00
n_gsm.c n_gsm: Fix timings 2011-11-08 10:10:20 -08:00
n_hdlc.c tty: n_hdlc not atomic use tty->flags. 2011-11-30 21:30:49 +09:00
n_r3964.c Revert "tty: make receive_buf() return the amout of bytes received" 2011-06-04 06:33:24 +09:00
n_tracerouter.c n_tracerouter and n_tracesink ldisc additions. 2011-05-13 16:31:00 -07:00
n_tracesink.c n_tracerouter and n_tracesink ldisc additions. 2011-05-13 16:31:00 -07:00
n_tracesink.h n_tracerouter and n_tracesink ldisc additions. 2011-05-13 16:31:00 -07:00
n_tty.c drivers/tty: Remove unneeded spaces 2011-12-09 19:11:35 -08:00
nozomi.c Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-05-26 13:19:00 -07:00
pty.c tty: move pty count limiting into devpts 2012-01-24 14:00:41 -08:00
rocket_int.h tty: move a number of tty drivers from drivers/char/ to drivers/tty/ 2011-02-22 16:14:56 -08:00
rocket.c module_param: make bool parameters really bool (drivers & misc) 2012-01-13 09:32:20 +10:30
rocket.h tty: move a number of tty drivers from drivers/char/ to drivers/tty/ 2011-02-22 16:14:56 -08:00
synclink_gt.c Fix common misspellings 2011-03-31 11:26:23 -03:00
synclink.c module_param: make bool parameters really bool (drivers & misc) 2012-01-13 09:32:20 +10:30
synclinkmp.c module_param: make bool parameters really bool (drivers & misc) 2012-01-13 09:32:20 +10:30
sysrq.c fs: move code out of buffer.c 2012-01-03 22:54:07 -05:00
tty_audit.c tty_audit: fix tty_audit_add_data live lock on audit disabled 2011-03-07 12:04:50 -08:00
tty_buffer.c tty_buffer: get rid of 'seen_tail' logic in flush_to_ldisc 2011-06-08 07:46:30 -07:00
tty_io.c tty: cleanup prohibition of direct opening for unix98 pty master 2012-01-24 13:56:10 -08:00
tty_ioctl.c tty: Support compat_ioctl get/set termios_locked 2011-10-18 14:17:11 -07:00
tty_ldisc.c Merge 3.2-rc3 into tty-next to handle merge conflict in tty_ldisc.c 2011-11-26 20:07:25 -08:00
tty_mutex.c TTY: remove tty_locked 2011-08-23 10:34:07 -07:00
tty_port.c TTY: use tty_wait_until_sent_from_close in tty_port_close_start 2011-08-25 09:00:41 -07:00