The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT.
The driver splits the locking function into two parts: local_irq_save() and
uart_port_lock() and this breaks PREEMPT_RT.
Delay handling sysrq until port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-2-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fix the following messages from checkpatch:
$ ./scripts/checkpatch.pl --strict --file \
drivers/tty/serial/amba-pl011.c
ERROR: do not initialise statics to false
WARNING: Possible unnecessary 'out of memory' message
WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
WARNING: Prefer [subsystem eg: netdev]_info([subsystem]dev, ... then
dev_info(dev, ... then pr_info(... to
CHECK: Prefer using the BIT macro
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20231207-mbly-uart-v6-6-e384afa5e78c@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fix the following checkpatch warnings & checks:
$ ./scripts/checkpatch.pl --strict --file \
drivers/tty/serial/amba-pl011.c
CHECK: Unbalanced braces around else statement
CHECK: Unnecessary parentheses around '[...]'
CHECK: braces {} should be used on all arms of this statement
CHECK: Comparison to NULL could be written "[...]"
WARNING: Comparisons should place the constant on the right side of the test
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20231207-mbly-uart-v6-5-e384afa5e78c@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The driver uses two TIOCMBIT macros inside pl011_{get,set}_mctrl to
simplify the logic. Those look scary to checkpatch because they contain
ifs without do-while loops.
Avoid the macros by creating small equivalent static functions; that
lets the compiler do its type checking & avoids checkpatch errors.
For the second instance __assign_bit is not usable because it deals with
unsigned long pointers whereas we have an unsigned int in
pl011_set_mctrl.
This addresses the following checkpatch warnings:
$ ./scripts/checkpatch.pl --strict --file \
drivers/tty/serial/amba-pl011.c
ERROR: Macros starting with if should be enclosed by a do -
while loop to avoid possible if/else logic defects
CHECK: Macro argument 'uartbit' may be better as '(uartbit)' to
avoid precedence issues
ERROR: Macros starting with if should be enclosed by a do - while
loop to avoid possible if/else logic defects
CHECK: Macro argument 'tiocmbit' may be better as '(tiocmbit)' to
avoid precedence issues
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20231207-mbly-uart-v6-3-e384afa5e78c@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Follow recommandations from:
$ ./scripts/checkpatch.pl --strict --file \
drivers/tty/serial/amba-pl011.c
We fix 5 warnings and 48 checks, all related to whitespace.
Culprits are:
CHECK: Alignment should match open parenthesis
CHECK: Blank lines aren't necessary after an open brace '{'
CHECK: Lines should not end with a '('
CHECK: Please don't use multiple blank lines
CHECK: Please use a blank line after function/struct/union/enum
declarations
CHECK: spaces preferred around that '/' (ctx:VxV)
CHECK: spaces preferred around that '|' (ctx:VxV)
WARNING: Missing a blank line after declarations
WARNING: please, no spaces at the start of a line
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20231207-mbly-uart-v6-2-e384afa5e78c@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().
Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20231110152927.70601-7-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Many SoCs do not integrate DMA for the amba pl011 UART, causing
the following message on boot:
uart-pl011 80074000.serial: no DMA platform data
The UART still works in PIO, so better not to print such message that
may confuse people by causing them to think that there is something wrong
with the UART.
Change the message to debug level.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Link: https://lore.kernel.org/r/20230928145842.466933-1-festevam@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When a serial port is used for kernel console output, then all
modifications to the UART registers which are done from other contexts,
e.g. getty, termios, are interference points for the kernel console.
So far this has been ignored and the printk output is based on the
principle of hope. The rework of the console infrastructure which aims to
support threaded and atomic consoles, requires to mark sections which
modify the UART registers as unsafe. This allows the atomic write function
to make informed decisions and eventually to restore operational state. It
also allows to prevent the regular UART code from modifying UART registers
while printk output is in progress.
All modifications of UART registers are guarded by the UART port lock,
which provides an obvious synchronization point with the console
infrastructure.
To avoid adding this functionality to all UART drivers, wrap the
spin_[un]lock*() invocations for uart_port::lock into helper functions
which just contain the spin_[un]lock*() invocations for now. In a
subsequent step these helpers will gain the console synchronization
mechanisms.
Converted with coccinelle. No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20230914183831.587273-18-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The DT of_device.h and of_platform.h date back to the separate
of_platform_bus_type before it as merged into the regular platform bus.
As part of that merge prepping Arm DT support 13 years ago, they
"temporarily" include each other. They also include platform_device.h
and of.h. As a result, there's a pretty much random mix of those include
files used throughout the tree. In order to detangle these headers and
replace the implicit includes with struct declarations, users need to
explicitly include the correct includes.
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # for imx
Link: https://lore.kernel.org/r/20230724205440.767071-1-robh@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
UART011_CR_RXE is set in pl011_startup() during normal initialization, and
cleared by pl011_disable_uart() during port shutdown.
You can use a none-console port in poll mode like kgdboc does with
tty_find_polling_driver() after a port shutdown. But pl011_startup() is not
called in tty_find_polling_driver(). So you need to set UART011_CR_RXE to
reenable receive function.
Not sure setting UART011_CR_RXE in pl011_set_termios() is a good idea
through.
Signed-off-by: Hongyu Xie <xiehongyu1@kylinos.cn>
Link: https://lore.kernel.org/r/20230501070909.1144547-1-xiehongyu1@kylinos.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Chapter "B Generic UART" in "ARM Server Base System Architecture" [1]
documentation describes a generic UART interface. Such generic UART
does not support DMA. In current code, sbsa_uart_pops and
amba_pl011_pops share the same stop_rx operation, which will invoke
pl011_dma_rx_stop, leading to an access of the DMACR register. This
commit adds a using_rx_dma check in pl011_dma_rx_stop to avoid the
access to DMACR register for SBSA UARTs which does not support DMA.
When the kernel enables DMA engine with "CONFIG_DMA_ENGINE=y", Linux
SBSA PL011 driver will access PL011 DMACR register in some functions.
For most real SBSA Pl011 hardware implementations, the DMACR write
behaviour will be ignored. So these DMACR operations will not cause
obvious problems. But for some virtual SBSA PL011 hardware, like Xen
virtual SBSA PL011 (vpl011) device, the behaviour might be different.
Xen vpl011 emulation will inject a data abort to guest, when guest is
accessing an unimplemented UART register. As Xen VPL011 is SBSA
compatible, it will not implement DMACR register. So when Linux SBSA
PL011 driver access DMACR register, it will get an unhandled data abort
fault and the application will get a segmentation fault:
Unhandled fault at 0xffffffc00944d048
Mem abort info:
ESR = 0x96000000
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x00: ttbr address size fault
Data abort info:
ISV = 0, ISS = 0x00000000
CM = 0, WnR = 0
swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000020e2e000
[ffffffc00944d048] pgd=100000003ffff803, p4d=100000003ffff803, pud=100000003ffff803, pmd=100000003fffa803, pte=006800009c090f13
Internal error: ttbr address size fault: 96000000 [#1] PREEMPT SMP
...
Call trace:
pl011_stop_rx+0x70/0x80
tty_port_shutdown+0x7c/0xb4
tty_port_close+0x60/0xcc
uart_close+0x34/0x8c
tty_release+0x144/0x4c0
__fput+0x78/0x220
____fput+0x1c/0x30
task_work_run+0x88/0xc0
do_notify_resume+0x8d0/0x123c
el0_svc+0xa8/0xc0
el0t_64_sync_handler+0xa4/0x130
el0t_64_sync+0x1a0/0x1a4
Code: b9000083 b901f001 794038a0 8b000042 (b9000041)
---[ end trace 83dd93df15c3216f ]---
note: bootlogd[132] exited with preempt_count 1
/etc/rcS.d/S07bootlogd: line 47: 132 Segmentation fault start-stop-daemon
This has been discussed in the Xen community, and we think it should fix
this in Linux. See [2] for more information.
[1] https://developer.arm.com/documentation/den0094/c/?lang=en
[2] https://lists.xenproject.org/archives/html/xen-devel/2022-11/msg00543.html
Fixes: 0dd1e247fd (drivers: PL011: add support for the ARM SBSA generic UART)
Signed-off-by: Jiamei Xie <jiamei.xie@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Link: https://lore.kernel.org/r/20221117103237.86856-1-jiamei.xie@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull tty / serial driver updates from Greg KH:
"Here is the big set of tty and serial driver changes for 6.0-rc1.
It was delayed from last week as I wanted to make sure the last commit
here got some good testing in linux-next and elsewhere as it seemed to
show up only late in testing for some reason.
Nothing major here, just lots of cleanups from Jiri and Ilpo to make
the tty core cleaner (Jiri) and the rs485 code simpler to use (Ilpo).
Also included in here is the obligatory n_gsm updates from Daniel
Starke and lots of tiny driver updates and minor fixes and tweaks for
other smaller serial drivers.
All of these have been in linux-next for a while with no reported
problems"
* tag 'tty-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (186 commits)
tty: serial: qcom-geni-serial: Fix %lu -> %u in print statements
tty: amiserial: Fix comment typo
tty: serial: document uart_get_console()
tty: serial: serial_core, reformat kernel-doc for functions
Documentation: serial: link uart_ops properly
Documentation: serial: move GPIO kernel-doc to the functions
Documentation: serial: dedup kernel-doc for uart functions
Documentation: serial: move uart_ops documentation to the struct
dt-bindings: serial: snps-dw-apb-uart: Document Rockchip RV1126
serial: mvebu-uart: uart2 error bits clearing
tty: serial: fsl_lpuart: correct the count of break characters
serial: stm32: make info structs static to avoid sparse warnings
serial: fsl_lpuart: zero out parity bit in CS7 mode
tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which otherwise could return a sub-optimal clock rate.
serial: 8250_bcm2835aux: Add missing clk_disable_unprepare()
tty: vt: initialize unicode screen buffer
serial: remove VR41XX serial driver
serial: 8250: lpc18xx: Remove redundant sanity check for RS485 flags
serial: 8250_dwlib: remove redundant sanity check for RS485 flags
dt_bindings: rs485: Correct delay values
...
The current timeout for draining the tx fifo in RS485 mode is calculated by
multiplying the time it takes to transmit one character (with the given
baud rate) with the maximal number of characters in the tx queue.
This timeout is too short for two reasons:
First when calculating the time to transmit one character integer division
is used which may round down the result in case of a remainder of the
division.
Fix this by rounding up the division result.
Second the hardware may need additional time (e.g for first putting the
characters from the fifo into the shift register) before the characters are
actually put onto the wire.
To be on the safe side double the current maximum number of iterations
that are used to wait for the queue draining.
Fixes: 8d47923772 ("serial: amba-pl011: add RS485 support")
Cc: stable@vger.kernel.org
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Link: https://lore.kernel.org/r/20220408233503.7251-1-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In uart_set_rs485_config() the serial core already
- ensures that only one of both options RTS on send or RTS after send is
set
- nullifies the padding field of the passed serial_rs485 struct
- clamps the RTS delays
- assigns the passed serial_rs485 struct to the uart port
So remove these tasks from the code of the drivers rs485_config() function
to avoid redundancy.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Link: https://lore.kernel.org/r/20220410104642.32195-3-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
RTS polarity of rs485-enabled ports is currently initialized on uart
open via:
tty_port_open()
tty_port_block_til_ready()
tty_port_raise_dtr_rts() # if (C_BAUD(tty))
uart_dtr_rts()
uart_port_dtr_rts()
There's at least three problems here:
First, if no baud rate is set, RTS polarity is not initialized.
That's the right thing to do for rs232, but not for rs485, which
requires that RTS is deasserted unconditionally.
Second, if the DeviceTree property "linux,rs485-enabled-at-boot-time" is
present, RTS should be deasserted as early as possible, i.e. on probe.
Otherwise it may remain asserted until first open.
Third, even though RTS is deasserted on open and close, it may
subsequently be asserted by uart_throttle(), uart_unthrottle() or
uart_set_termios() because those functions aren't rs485-aware.
(Only uart_tiocmset() is.)
To address these issues, move RTS initialization from uart_port_dtr_rts()
to uart_configure_port(). Prevent subsequent modification of RTS
polarity by moving the existing rs485 check from uart_tiocmget() to
uart_update_mctrl().
That way, RTS is initialized on probe and then remains unmodified unless
the uart transmits data. If rs485 is enabled at runtime (instead of at
boot) through a TIOCSRS485 ioctl(), RTS is initialized by the uart
driver's ->rs485_config() callback and then likewise remains unmodified.
The PL011 driver initializes RTS on uart open and prevents subsequent
modification in its ->set_mctrl() callback. That code is obsoleted by
the present commit, so drop it.
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Su Bao Cheng <baocheng.su@siemens.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/2d2acaf3a69e89b7bf687c912022b11fd29dfa1e.1642909284.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit d8d8ffa477 ("amba-pl011: do not disable RTS during shutdown")
amended the PL011 serial driver to leave DTR/RTS polarity untouched on
tty close. That change made sense.
But the commit also added code to save DTR/RTS state to an internal
variable on tty close and restore it on tty open. That part of the
commit makes less sense: The driver has no ->pm() callback, so the uart
remains powered after tty close and automatically preserves register
state, including DTR/RTS.
Saving and restoring registers isn't the job of the ->startup() and
->shutdown() callbacks anyway. Rather, it should happen in ->pm().
Additionally, after pl011_startup() restores the state, the serial core
overrides it in uart_port_dtr_rts() if a baud rate has been set:
tty_port_open()
uart_port_activate()
uart_startup()
uart_port_startup()
pl011_startup() # restores DTR/RTS from uap->old_cr
tty_port_block_til_ready()
tty_port_raise_dtr_rts # if (C_BAUD(tty))
uart_dtr_rts()
uart_port_dtr_rts() # raises DTR/RTS
The serial core also overrides DTR/RTS on tty close in uart_shutdown()
if C_HUPCL(tty) is set. So a user-defined DTR/RTS polarity won't
survive a close/open cycle anyway, unless the user has set the baud rate
to zero and disabled hupcl on the tty.
Bottom line is, the code to save and restore DTR/RTS has no effect.
Remove it.
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/e22089ab49e6e78822c50c8c4db46bf3ee885623.1641129328.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pl011_set_termios() briefly resets the CR register to zero, thereby
glitching DTR/RTS signals. With rs485 this may result in the bus being
occupied for no reason.
Where does this register write originate from?
The PL011 driver was forked from the PL010 driver in 2004:
https://git.kernel.org/history/history/c/157c0342e591
Until this commit, the PL010 driver's IRQ handler ambauart_int()
modified the CR register without holding the port spinlock.
ambauart_set_termios() also modified that register. To prevent
concurrent read-modify-writes by the IRQ handler and to prevent
transmission while changing baudrate, ambauart_set_termios() had to
disable interrupts. On the PL010, that is achieved by writing zero to
the CR register.
However, on the PL011, interrupts are disabled in the IMSC register,
not in the CR register.
Additionally, the commit amended both the PL010 and PL011 driver to
acquire the port spinlock in the IRQ handler, obviating the need to
disable interrupts in ->set_termios().
So the CR register write is obsolete for two reasons. Drop it.
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/f49f945375f5ccb979893c49f1129f51651ac738.1641129062.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
With commit 3873e2d7f6 ("drivers: PL011: refactor pl011_probe()") the
function devm_ioremap() called from pl011_setup_port() was replaced with
devm_ioremap_resource(). Since this function not only remaps but also
requests the ports io memory region it now collides with the .config_port()
callback which requests the same region at uart port registration.
Since devm_ioremap_resource() already claims the memory successfully, the
request in .config_port() fails.
Later at uart port deregistration the attempt to release the unclaimed
memory also fails. The failure results in a “Trying to free nonexistent
resource" warning.
Fix these issues by removing the callbacks that implement the redundant
memory allocation/release. Also make sure that changing the drivers io
memory base address via TIOCSSERIAL is not allowed any more.
Fixes: 3873e2d7f6 ("drivers: PL011: refactor pl011_probe()")
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Link: https://lore.kernel.org/r/20211129174238.8333-1-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 89d4f98ae9 ("ARM: remove zte zx platform") missed to remove some
definitions for this platform's debug and serial, e.g., code dependent on
the config DEBUG_ZTE_ZX.
Fortunately, ./scripts/checkkconfigsymbols.py detects this and warns:
DEBUG_ZTE_ZX
Referencing files: arch/arm/include/debug/pl01x.S
Further review by Arnd Bergmann identified even more dead code in the
amba serial driver.
Remove all this left-over from the zte zx platform.
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20211102063810.932-1-lukas.bulwahn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The document 'ACPI for Arm Components 1.0' defines the following
_HID mappings:
-'Prime cell UART (PL011)': ARMH0011
-'SBSA UART': ARMHB000
Use the sbsa-uart driver when a device is described with
the 'ARMHB000' _HID.
Note:
PL011 devices currently use the sbsa-uart driver instead of the
uart-pl011 driver. Indeed, PL011 devices are not bound to a clock
in ACPI. It is not possible to change their baudrate.
Cc: <stable@vger.kernel.org>
Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Link: https://lore.kernel.org/r/20211109172248.19061-1-Pierre.Gondois@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In order to make pl011 work better, multiple interrupts are
required, such as TXIM, RXIM, RTIM, error interrupt(FE/PE/BE/OE);
at the same time, pl011 to GIC does not merge the interrupt
lines(each serial-interrupt corresponding to different GIC hardware
interrupt), so need to enable and request multiple gic interrupt
numbers in the driver.
Signed-off-by: Bing Fan <tombinfan@tencent.com>
Link: https://lore.kernel.org/r/1625103512-30182-1-git-send-email-hptsfb@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add basic support for RS485: Provide a callback to configure RS485
settings. Handle the RS485 specific part in the functions
pl011_rs485_tx_start() and pl011_rs485_tx_stop() which extend the generic
start/stop callbacks.
Beside via IOCTL from userspace RS485 can be enabled by means of the
device tree property "rs485-enabled-at-boot-time".
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Link: https://lore.kernel.org/r/20210630225644.3744-1-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
