1
linux/drivers
Russell King 68b65f7305 ARM: PL011: Add support for transmit DMA
Add DMA engine support for transmit to the PL011 driver.  Based on a
patch from Linus Walliej, with the following changes:

- remove RX DMA support.  As PL011 doesn't give us receive timeout
  interrupts, we only get notified of received data when the RX DMA
  has completed.  This rather sucks for interactive use of the TTY.

- remove abuse of completions.  Completions are supposed to be for
  events, not to tell what condition buffers are in.  Replace it with
  a simple 'queued' bool.

- fix locking - it is only safe to access the circular buffer with the
  port lock held.

- only map the DMA buffer when required - if we're ever behind an IOMMU
  this helps keep IOMMU usage down, and also ensures that we're legal
  when we change the scatterlist entry length.

- fix XON/XOFF sending - we must send XON/XOFF characters out as soon
  as possible - waiting for up to 4095 characters in the DMA buffer
  to be sent first is not acceptable.

- fix XON/XOFF receive handling - we need to stop DMA when instructed
  to by the TTY layer, and restart it again when instructed to.  There
  is a subtle problem here: we must not completely empty the circular
  buffer with DMA, otherwise we will not be notified of XON.

- change the 'enable_dma' flag into a 'using DMA' flag, and track
  whether we can use TX DMA by whether the channel pointer is non-NULL.
  This gives us more control over whether we use DMA in the driver.

- we don't need to have the TX DMA buffer continually allocated for
  each port - instead, allocate it when the port starts up, and free
  it when it's shut down.  Update the 'using DMA' flag if we get
  the buffer, and adjust the TTY FIFO size appropriately.

- if we're going to use PIO to send characters, use the existing IRQ
  based functionality rather than reimplementing it.  This also ensures
  we call uart_write_wakeup() at the appropriate time, otherwise we'll
  stall.

- use DMA engine helper functions for type safety.

- fix init when built as a module - we can't have to initcall functions,
  so we must settle on one.  This means we can eliminate the deferred
  DMA initialization.

- there is no need to terminate transfers on a failed prep_slave_sg()
  call - nothing has been setup, so nothing needs to be terminated.
  This avoids a potential deadlock in the DMA engine code
  (tasklet->callback->failed prepare->terminate->tasklet_disable
   which then ends up waiting for the tasklet to finish running.)

- Dan says that the submission callback should not return an error:
  | dma_submit_error() is something I should have removed after commit
  | a0587bcf "ioat1: move descriptor allocation from submit to prep" all
  | errors should be notified by prep failing to return a descriptor
  | handle.  Negative dma_cookie_t values are only returned by the
  | dma_async_memcpy* calls which translate a prep failure into -ENOMEM.
  So remove the error handling at that point.  This also solves the
  potential deadlock mentioned in the previous comment.

Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-05 16:58:48 +00:00
..
accessibility
acpi Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2010-10-26 17:28:37 -07:00
amba
ata ATA: pata_octeon_cf: Use I/O clock rate for timing calculations. 2010-10-29 19:08:41 +01:00
atm drivers/atm/eni.c: Remove multiple uses of KERN_<level> 2010-10-26 11:35:37 -07:00
auxdisplay
base Merge branch 'pm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/suspend-2.6 2010-10-29 15:09:56 -07:00
block floppy: fix another use-after-free 2010-11-06 07:49:56 -07:00
bluetooth
cdrom cdrom: gdrom: ctrl_in/outX to __raw_read/writeX conversion. 2010-10-27 14:33:39 +09:00
char TTY: move .gitignore from drivers/char/ to drivers/tty/vt/ 2010-11-05 22:18:23 -07:00
clocksource ARM: shmobile: remove sh_timer_config clk member 2010-10-31 10:40:39 -04:00
connector
cpufreq
cpuidle
crypto replace nested max/min macros with {max,min}3 macro 2010-10-26 16:52:12 -07:00
dca
dio
dma drivers/dma/Kconfig: add part number for Topcliff. 2010-10-29 14:14:02 -07:00
edac Merge branch 'linux_next' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/i7core 2010-10-26 10:13:48 -07:00
eisa
firewire Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 2010-11-05 14:17:22 -07:00
firmware dmi: log board, system, and BIOS information 2010-10-27 18:03:05 -07:00
gpio gpio: Add VIA VX855 GPIO driver 2010-10-29 00:29:51 +02:00
gpu Merge branch 'drm-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6 2010-10-27 20:37:06 -07:00
hid
hwmon hwmon: (ltc4261) Fix error message format 2010-11-05 10:17:19 -07:00
i2c i2c-i801: Add PCI idents for Patsburg 'IDF' SMBus controllers 2010-10-31 21:07:00 +01:00
ide ide: clean up timed out request handling 2010-10-26 10:17:30 -07:00
idle Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6 2010-10-26 17:28:07 -07:00
ieee802154
infiniband convert get_sb_single() users 2010-10-29 04:16:28 -04:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2010-10-31 21:02:39 -04:00
isdn Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2010-11-05 15:25:48 -07:00
leds leds-net5501: taints kernel, add license 2010-11-05 09:51:56 -07:00
lguest
macintosh Move ams driver to macintosh 2010-10-28 20:31:50 +02:00
mca
md md: tidy up device searches in read_balance. 2010-10-29 16:40:33 +11:00
media Input: ir-keytable - fix uninitialized variable warning 2010-10-31 21:05:43 -04:00
memstick
message
mfd mfd: Fix a memory leak when unload mc13xxx-core module 2010-10-29 00:30:43 +02:00
misc Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb 2010-10-29 11:49:38 -07:00
mmc mfd: Adding twl6030 mmc card detect support for MMC1 2010-10-29 00:29:59 +02:00
mtd Merge git://git.infradead.org/mtd-2.6 2010-10-30 08:31:35 -07:00
net ipw2x00: remove the right /proc/net entry 2010-11-05 18:57:04 -07:00
nubus
of
oprofile Merge branches 'perf-fixes-for-linus' and 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-30 11:43:26 -07:00
parisc Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/kyle/parisc-2.6 2010-10-28 09:24:14 -07:00
parport
pci Merge branch 'stable/xen-pcifront-0.8.2' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2010-10-28 17:11:17 -07:00
pcmcia
platform Remove duplicate includes from many files 2010-10-27 18:03:18 -07:00
pnp Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2010-10-26 17:28:37 -07:00
power power: Revert "power_supply: Mark twl4030_charger as broken" 2010-10-29 00:30:44 +02:00
pps
ps3
rapidio rapidio: fix destructive port EM initialization for Tsi568 2010-10-27 18:03:16 -07:00
regulator regulator: max8998 BUCK1/2 voltage change with use of GPIOs 2010-10-29 00:30:15 +02:00
rtc sh: mach-snapgear: Kill off machtype, consolidate board def. 2010-10-29 19:06:53 +09:00
s390 Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2010-10-31 20:43:12 -04:00
sbus
scsi [SCSI] pmcraid: add support for set timestamp command and other fixes 2010-10-29 12:03:01 -05:00
serial ARM: PL011: Add support for transmit DMA 2011-01-05 16:58:48 +00:00
sfi
sh Merge branches 'sh/pio-death', 'sh/nommu', 'sh/clkfwk', 'sh/core' and 'sh/intc-extension' into sh-fixes-for-linus 2010-11-08 09:42:43 +09:00
sn
spi Merge branch 'next-spi' of git://git.secretlab.ca/git/linux-2.6 2010-11-01 07:50:43 -04:00
ssb
staging Staging: ath6kl: remove empty files that mess with 'distclean' 2010-11-06 11:27:04 -07:00
tc
telephony
thermal
tty TTY: move .gitignore from drivers/char/ to drivers/tty/vt/ 2010-11-05 22:18:23 -07:00
uio
usb Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2010-11-05 15:25:48 -07:00
uwb
vhost
video Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm 2010-10-30 08:26:25 -07:00
virtio
vlynq
w1 w1: don't allow arbitrary users to remove w1 devices 2010-10-27 18:03:17 -07:00
watchdog WATCHDOG: octeon-wdt: Use I/O clock rate for timing calculations. 2010-10-29 19:08:42 +01:00
xen convert get_sb_single() users 2010-10-29 04:16:28 -04:00
zorro
Kconfig
Makefile TTY: create drivers/tty and move the tty core files there 2010-11-05 08:10:33 -07:00