commit fb78b81142 provide a workaround for
kernel panic, but bring potential deadlock risk. that is in
sirfsoc_rx_tmo_process_tl while enter into sirfsoc_uart_pio_rx_chars
cpu hold uart_port->lock, if uart interrupt comes cpu enter into
sirfsoc_uart_isr and deadlock occurs in getting uart_port->lock.
the patch replace spin_lock version to spin_lock_irq* version to avoid
spinlock dead lock issue. let function tty_flip_buffer_push in tasklet
outof spin_lock_irq* protect area to avoid add the pair of spin_lock and
spin_unlock for tty_flip_buffer_push.
BTW drop self defined unused spinlock protect of tx_lock/rx_lock.
56274.220464] BUG: spinlock lockup suspected on CPU#0, swapper/0/0
[56274.223648] lock: 0xc05d9db0, .magic: dead4ead, .owner: swapper/0/0,
.owner_cpu: 0
[56274.231278] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G
O 3.10.35 #1
[56274.238241] [<c0015530>] (unwind_backtrace+0x0/0xf4) from
[<c00120d8>] (show_stack+0x10/0x14)
[56274.246742] [<c00120d8>] (show_stack+0x10/0x14) from
[<c01b11b0>] (do_raw_spin_lock+0x110/0x184)
[56274.255501] [<c01b11b0>] (do_raw_spin_lock+0x110/0x184) from
[<c02124c8>] (sirfsoc_uart_isr+0x20/0x42c)
[56274.264874] [<c02124c8>] (sirfsoc_uart_isr+0x20/0x42c) from
[<c0075790>] (handle_irq_event_percpu+0x54/0x17c)
[56274.274758] [<c0075790>] (handle_irq_event_percpu+0x54/0x17c)
from [<c00758f4>] (handle_irq_event+0x3c/0x5c)
[56274.284561] [<c00758f4>] (handle_irq_event+0x3c/0x5c) from
[<c0077fa0>] (handle_level_irq+0x98/0xfc)
[56274.293670] [<c0077fa0>] (handle_level_irq+0x98/0xfc) from
[<c0074f44>] (generic_handle_irq+0x2c/0x3c)
[56274.302952] [<c0074f44>] (generic_handle_irq+0x2c/0x3c) from
[<c000ef80>] (handle_IRQ+0x40/0x90)
[56274.311706] [<c000ef80>] (handle_IRQ+0x40/0x90) from
[<c000dc80>] (__irq_svc+0x40/0x70)
[56274.319697] [<c000dc80>] (__irq_svc+0x40/0x70) from
[<c038113c>] (_raw_spin_unlock_irqrestore+0x10/0x48)
[56274.329158] [<c038113c>]
(_raw_spin_unlock_irqrestore+0x10/0x48) from [<c0200034>]
(tty_port_tty_get+0x58/0x90)
[56274.339213] [<c0200034>] (tty_port_tty_get+0x58/0x90) from
[<c0212008>] (sirfsoc_uart_pio_rx_chars+0x1c/0xc8)
[56274.349097] [<c0212008>]
(sirfsoc_uart_pio_rx_chars+0x1c/0xc8) from [<c0212ef8>]
(sirfsoc_rx_tmo_process_tl+0xe4/0x1fc)
[56274.359853] [<c0212ef8>]
(sirfsoc_rx_tmo_process_tl+0xe4/0x1fc) from [<c0027c04>]
(tasklet_action+0x84/0x114)
[56274.369739] [<c0027c04>] (tasklet_action+0x84/0x114) from
[<c0027db4>] (__do_softirq+0x120/0x200)
[56274.378585] [<c0027db4>] (__do_softirq+0x120/0x200) from
[<c0027f44>] (do_softirq+0x54/0x5c)
[56274.386998] [<c0027f44>] (do_softirq+0x54/0x5c) from
[<c00281ec>] (irq_exit+0x9c/0xd0)
[56274.394899] [<c00281ec>] (irq_exit+0x9c/0xd0) from
[<c000ef84>] (handle_IRQ+0x44/0x90)
[56274.402790] [<c000ef84>] (handle_IRQ+0x44/0x90) from
[<c000dc80>] (__irq_svc+0x40/0x70)
[56274.410774] [<c000dc80>] (__irq_svc+0x40/0x70) from
[<c0288af4>] (cpuidle_enter_state+0x50/0xe0)
[56274.419532] [<c0288af4>] (cpuidle_enter_state+0x50/0xe0) from
[<c0288c34>] (cpuidle_idle_call+0xb0/0x148)
[56274.429080] [<c0288c34>] (cpuidle_idle_call+0xb0/0x148) from
[<c000f3ac>] (arch_cpu_idle+0x8/0x38)
[56274.438016] [<c000f3ac>] (arch_cpu_idle+0x8/0x38) from
[<c0059344>] (cpu_startup_entry+0xfc/0x140)
[56274.446956] [<c0059344>] (cpu_startup_entry+0xfc/0x140) from
[<c04a3a54>] (start_kernel+0x2d8/0x2e4)
Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
All SiRFSoC UART registers are in 32-bits. If we use writeb for
TXFIFO, actually all of 32-bits are still written, for TXTIFO,
only low 8-bits are valid, so in prima2&atlas6, this causes no
problem.
But in the new atlas7, using writeb to write UART registers will
cause an imprecise data abort as HW does check the "wrong" writeb.
So move to writel and this also makes the code consistent with
sirfsoc_uart_pio_tx_chars() in which we use writel.
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Two new drivers have been added since 3.14, the MEN 16z135 uart, and
the ARM semihosting console. Both are missing an explicit 'select
SERIAL_CORE', which can leads build errors when no other driver
selects the core, as found during ARM randconfig testing.
In case of the ARM semihosting console, we also have to select
SERIAL_CORE_CONSOLE.
This adds the missing 'select' statements.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This fixes the warnings:
drivers/tty/serial/sc16is7xx.c: In function 'sc16is7xx_handle_rx':
>> drivers/tty/serial/sc16is7xx.c:548:1: warning: 'sc16is7xx_handle_rx' uses dynamic stack allocation [enabled by default]
drivers/tty/serial/sc16is7xx.c: In function 'sc16is7xx_handle_tx':
>> drivers/tty/serial/sc16is7xx.c:589:1: warning: 'sc16is7xx_handle_tx' uses dynamic stack allocation [enabled by default]
Signed-off-by: Jon Ringle <jringle@gridpoint.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/serial/sc16is7xx.c:1060:12: warning: 'sc16is7xx_probe' defined but not used [-Wunused-function]
static int sc16is7xx_probe(struct device *dev,
^
drivers/tty/serial/sc16is7xx.c:1176:12: warning: 'sc16is7xx_remove' defined but not used [-Wunused-function]
static int sc16is7xx_remove(struct device *dev)
^
drivers/tty/serial/sc16is7xx.c:1215:29: warning: 'regcfg' defined but not used [-Wunused-variable]
static struct regmap_config regcfg = {
^
Fixed these warnings by removing the `#ifdef CONFIG_REGMAP_I2C' around their
calls as this driver selects REGMAP_I2C in Kconfig. This part of driver just
didn't compile at all when REGMAP_I2C configured as module (CONFIG_REGMAP_I2C
is not defined, just CONFIG_REGMAP_I2C_MODULE).
Signed-off-by: Jan Moskyto Matejka <mq@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
On initialization failure, an error message is already printed with
level KERN_ERR, no need to print another one with level KERN_INFO.
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The pch_uart driver is for a companion chip to the Intel Atom E600
series processors. These are 32-bit x86 processors so the driver is
only needed on X86_32. Add COMPILE_TEST as an alternative, so that the
driver can still be build-tested elsewhere.
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 9aac588759 (tty/serial: add generic serial earlycon) moved
console option parsing from 8250_early.c and converted to kstrto*
functions from simple_strtoul along the way. However, kstrto* functions
are not equivalent in that they do not allow non-convertible characters
at the end such as "115200n8". Fix this by changing back to
simple_strtoul and ignore what checkpatch.pl says.
Reported-by: Yinghai Lu <yinghai@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit d2fd6810a8 (tty/serial: convert 8250 to generic earlycon)
removed setup_early_serial8250_console, but there are still 2 callers
in:
arch/mips/mti-malta/malta-init.c
drivers/firmware/pcdp.c
Add back the function implemented as a wrapper to setup_earlycon.
Reported-by: Yinghai Lu <yinghai@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fix by including linux/uaccess.h:
drivers/tty/serial/sc16is7xx.c: In function 'sc16is7xx_ioctl':
>> drivers/tty/serial/sc16is7xx.c:861:3: error: implicit declaration of function 'copy_from_user' [-Werror=implicit-function-declaration]
>> drivers/tty/serial/sc16is7xx.c:867:3: error: implicit declaration of function 'copy_to_user' [-Werror=implicit-function-declaration]
Signed-off-by: Jon Ringle <jringle@gridpoint.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The SC16IS7xx is a slave I2C-bus/SPI interface to a single-channel
high performance UART. The SC16IS7xx's internal register set is
backward-compatible with the widely used and widely popular 16C450.
The SC16IS7xx also provides additional advanced features such as
auto hardware and software flow control, automatic RS-485 support, and
software reset.
Signed-off-by: Jon Ringle <jringle@gridpoint.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit fcbee4d49f.
It wasn't quite ready to go in yet, sorry about that.
Cc: Simon Horman <horms@verge.net.au>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add earlycon support for the arm/arm64 semihosting debug serial
interface. This allows enabling a debug console when early_params are
processed. This is based on the arm64 earlyprintk smh support and is
intended to replace it.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add earlycon support for the pl011 serial port. This allows enabling
the pl011 for console when early_params are processed. This is based
on the arm64 earlyprintk support and is intended to replace it.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
With the generic earlycon infrastructure in place, convert the 8250
early console to use it.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This introduces generic earlycon infrastructure for serial devices
based on the 8250 earlycon. This allows for supporting earlycon option
with other serial devices. The earlycon output is enabled at the time
early_params are processed.
Only architectures that have fixmap support or have functional ioremap
when early_params are processed are supported. This is the same
restriction that the 8250 driver had.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In preparation to support FIX_EARLYCON_MEM on other arches, make the
option per arch.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add driver for MEN's 16z135 High Speed UART.
The 16z135 is a memory mapped UART Core on an MCB FPGA and has 1024 byte
deep FIFO buffers for the RX and TX path. It also has configurable FIFO
fill level IRQs and data copied to and from the hardware has to be
acknowledged.
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@men.de>
Reviewed-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Zynq's UART is Cadence IP. Make this visible in the prompt in kconfig
and additional comments in the driver.
This also renames functions and symbols, as far as possible without
breaking user space API, to reflect the Cadence origin. This is achieved
through simple search and replace:
- s/XUARTPS/CDNS_UART/g
- s/xuartps/cdns_uart/g
The only exceptions are PORT_XUARTPS and the driver name, which stay as is,
due to their exposure to user space. As well as the - no legacy -
compatibility string 'xlnx,xuartps'
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
A comment states, that, according to the data sheet, to enable
interrupts the disable register should be written, but the enable
register could be left untouched. And it suspsects a HW bug requiring
to write both.
Reviewing the data sheet, these statements seem wrong. Just as one would
expect. Writing to the enable/disable register enables/disables
interrupts.
Hence the misleading comment and needless write to the disable register
are removed from the enable sequence.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
A lot of read-modify-write sequences used a one-line statement which
nests a readl() within a writel(). Convert this into code sequences that
make the three steps more obvious.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Print a warning if the clock notifier rejects a clock frequency change
to facilitate debugging (see:
http://thread.gmane.org/gmane.linux.ports.arm.kernel/304329/focus=304379)
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This is all white space and comment clean up. Mostly reformatting
comments.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Register port numbers according to order in DT aliases.
If aliases are not defined, order in DT is used.
If aliases are defined, register port id based
on that.
This patch ensures proper ttyPS0/1 assignment.
[soren]: Combined integer declarations in probe(), removed warning message
if no alias is found.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
nobody passes a DTR_gpio to this driver, so
this code is not necessary.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
just using helper function to remove some duplicated
code a bit. While at that, also move allocation of
struct uart_omap_port higher in the code so that
we return much earlier in case of no memory.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
this way we can remove one pointer declaration.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
this will make sure gpio gets freed automatically
when this device is destroyed.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
per CodingStyle we should have those braces, no
functional changes.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit 0324a82102.
That commit tried to fix a deadlock problem when using
hci_ldisc, but it turns out the bug was in hci_ldsic
all along where it was calling ->write() from within
->write_wakeup() callback.
The problem is that ->write_wakeup() was called with
port lock held and ->write() tried to grab the same
port lock.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In (efe2f29 kgdboc,kdb: Allow kdb to work on a non open console port)
support was added to directly use the "write_char" functions when
doing kdb over a non-open console port. This is great, but it ends up
bypassing the normal code in uart_console_write() that adds a carriage
return before any newlines.
There appears to have been a trend to add this support directly in
some console driver's poll_put_char() functions. This had a few side
effects, including:
- In this case we were doing LFCR, not CRLF. This was fixed in
uart_console_write() back in (d358788 [SERIAL] kernel console should
send CRLF not LFCR)
- Not all serial drivers had the LFCR code in their poll_put_char()
functions. In my case I was running serial/samsung.c which lacked
it.
I've moved the handling to uart_poll_put_char() to fix the above
problems. Now when I use kdb (and don't point console= to the same
UART) I no longer get:
[0]kdb>
[0]kdb>
[0]kdb>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use del_timer_sync to ensure that the timer is stopped on all CPUs before
the driver exists.
This change was suggested by Thomas Gleixner.
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@r@
declarer name module_exit;
identifier ex;
@@
module_exit(ex);
@@
identifier r.ex;
@@
ex(...) {
<...
- del_timer
+ del_timer_sync
(...)
...>
}
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The mux driver is anomalous among all the serial drivers that can
define SUPPORT_SYSRQ because it can, with some configs, set
SUPPORT_SYSRQ when SERIAL_CORE_CONSOLE is not set.
Not only does this impose a pointless (but tiny) runtime overhead for
such configs but, more significantly, it adds needless complexity when
doing a code review to check for unexpected side effects of any
changes to the serial core.
This is (cross-)compile tested only because I do not have any PA-RISC
hardware.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
According to the platform data for the legacy-C initialisation of sh-sci
for the r8a7779 SoC and my own testing the SCIx_SH4_SCIF_REGTYPE bit of
scscr needs to be set.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In the same manner as 8250_pci, 8250_dw needs some
baytrail specific quirks to be used. The reference
clock needs to be adjusted before divided in order
to have the minimum error rate on the baudrate.
The specific byt set termios function is stored in
the driver_data field of the acpi device id via the
dw8250_acpi_desc structure.
Remove the uartclk field which is no longer delivered
as driver data.
Signed-off-by: Loic Poulain <loic.poulain@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This will additionally show the specific UART device instead of the
general module name. This cames in handy so check for the interupts of
a specific device if there are several of them.
Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
While porting a RS485 driver from 2.6.29 to 3.14, i noticed that the serial tty
driver could break it by using uart ports that it does not own :
1. uart_change_pm ist called during uart_open and calls the uart pm function
without checking for PORT_UNKNOWN.
The fix is to move uart_change_pm from uart_open to uart_port_startup.
2. The return code from the uart request_port call in uart_set_info is not
handled properly, leading to the situation that the serial driver also
thinks it owns the uart ports.
This can triggered by doing following actions :
setserial /dev/ttyS0 uart none # release the uart ports
modprobe lirc-serial # or any other device that uses the uart
setserial /dev/ttyS0 uart 16550 # gives no error and the uart tty driver
# can use the ports as well
Signed-off-by: Thomas Pfaff <tpfaff@pcs.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The two functions to write out to the console (one used in normal
console mode and one in polling console mode) were slightly different.
One used a barrier() in its loop and the other a cpu_relax(). The
barrier() really doesn't do anything since we're using rd_regl() to
read the port anyway. Switch it to cpu_relax() to make things
consistent.
No known bugs / issues are fixed by this change--it just makes things
more consistent.
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The s3c24xx_serial_console_putchar() is _only_ ever used by
s3c24xx_serial_console_write() and is called in a loop (indirectly
through uart_console_write()). There's no reason to call
s3c24xx_port_configured() for every iteration through the loop. Move
it outside the loop.
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The two functions in the samsung serial driver used for writing
characters out to the port were inconsistent about whether they used
the passed in "port" or the global "cons_uart". There was no reason
to use the global and the use of the global in
s3c24xx_serial_put_poll_char() caused a crash in the case where you
used the serial port for kgdboc but not for console.
Fix it so we used the passed in variable.
Note that this doesn't fix all problems with the samsung serial
driver. Specifically:
* s3c24xx_serial_console_putchar() is still 99% identical to
s3c24xx_serial_put_poll_char() (the function signature is different,
but that's about it). A future patch will make them slightly less
identical and judging by other serial drivers we may need yet more
differences eventually.
* The samsung serial driver still doesn't allow you to have more than
one console port since it still uses the global cons_uart in
s3c24xx_serial_console_write().
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
__dma_tx_complete is not protected against concurrent
call of serial8250_tx_dma. it can lead to circular tail
index corruption or parallel call of serial_tx_dma on the
same data portion.
This patch fixes this issue by holding the port lock.
Signed-off-by: Loic Poulain <loic.poulain@intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
On transmit-hold-register empty, serial8250_tx_chars
should be called only if we don't use DMA.
DMA has its own tx cycle.
Signed-off-by: Loic Poulain <loic.poulain@intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The race was introduced while development of linux-3.11 by
e8437d7ecb and
e9975fdec0.
Originally it was found and reproduced on linux-3.12.15 and
linux-3.12.15-rt25, by sending 500 byte blocks with 115kbaud to the
target uart in a loop with 100 milliseconds delay.
In short:
1. The consumer flush_to_ldisc is on to remove the head tty_buffer.
2. The producer adds a number of bytes, so that a new tty_buffer must
be allocated and added by __tty_buffer_request_room.
3. The consumer removes the head tty_buffer element, without handling
newly committed data.
Detailed example:
* Initial buffer:
* Head, Tail -> 0: used=250; commit=250; read=240; next=NULL
* Consumer: ''flush_to_ldisc''
* consumed 10 Byte
* buffer:
* Head, Tail -> 0: used=250; commit=250; read=250; next=NULL
{{{
count = head->commit - head->read; // count = 0
if (!count) { // enter
// INTERRUPTED BY PRODUCER ->
if (head->next == NULL)
break;
buf->head = head->next;
tty_buffer_free(port, head);
continue;
}
}}}
* Producer: tty_insert_flip_... 10 bytes + tty_flip_buffer_push
* buffer:
* Head, Tail -> 0: used=250; commit=250; read=250; next=NULL
* added 6 bytes: head-element filled to maximum.
* buffer:
* Head, Tail -> 0: used=256; commit=250; read=250; next=NULL
* added 4 bytes: __tty_buffer_request_room is called
* buffer:
* Head -> 0: used=256; commit=256; read=250; next=1
* Tail -> 1: used=4; commit=0; read=250 next=NULL
* push (tty_flip_buffer_push)
* buffer:
* Head -> 0: used=256; commit=256; read=250; next=1
* Tail -> 1: used=4; commit=4; read=250 next=NULL
* Consumer
{{{
count = head->commit - head->read;
if (!count) {
// INTERRUPTED BY PRODUCER <-
if (head->next == NULL) // -> no break
break;
buf->head = head->next;
tty_buffer_free(port, head);
// ERROR: tty_buffer head freed -> 6 bytes lost
continue;
}
}}}
This patch reintroduces a spin_lock to protect this case. Perhaps later
a lock-less solution could be found.
Signed-off-by: Manfred Schlaegl <manfred.schlaegl@gmx.at>
Cc: stable <stable@vger.kernel.org> # 3.11
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit f4f653e987.
Jiri writes:
No, please drop this one. We need a better solution as it turned
out that some boxes need 16k loops and it will increase with new
processors :(.
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Martin Pluskal <mpluskal@suse.com>
Cc: Takashi Iwai <tiwai@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Qipan Li
Barry Song
Arnd Bergmann
Jon Ringle
Jan Moskyto Matejka
Jean Delvare
Rob Herring
Greg Kroah-Hartman
Johannes Thumshirn
Soren Brinkmann
Michal Simek
Felipe Balbi
Doug Anderson
Julia Lawall
Daniel Thompson
Simon Horman
Loic Poulain
Alexander Stein
Thomas Pfaff
Manfred Schlaegl