linux.git/include/linux/serial_core.h, branch v6.10-rc2

tty: serial: switch from circ_buf to kfifo

2024-04-09T13:28:03+00:00

Switch from struct circ_buf to proper kfifo. kfifo provides much better
API, esp. when wrap-around of the buffer needs to be taken into account.
Look at pl011_dma_tx_refill() or cpm_uart_tx_pump() changes for example.

Kfifo API can also fill in scatter-gather DMA structures, so it easier
for that use case too. Look at lpuart_dma_tx() for example. Note that
not all drivers can be converted to that (like atmel_serial), they
handle DMA specially.

Note that usb-serial uses kfifo for TX for ages.

omap needed a bit more care as it needs to put a char into FIFO to start
the DMA transfer when OMAP_DMA_TX_KICK is set. In that case, we have to
do kfifo_dma_out_prepare twice: once to find out the tx_size (to find
out if it is worths to do DMA at all -- size >= 4), the second time for
the actual transfer.

All traces of circ_buf are removed from serial_core.h (and its struct
uart_state).

Signed-off-by: Jiri Slaby (SUSE) 
Cc: Al Cooper 
Cc: Matthias Brugger 
Cc: AngeloGioacchino Del Regno 
Cc: Kumaravel Thiagarajan 
Cc: Tharun Kumar P 
Cc: Russell King 
Cc: Vineet Gupta 
Cc: Richard Genoud 
Cc: Nicolas Ferre 
Cc: Alexandre Belloni 
Cc: Claudiu Beznea 
Cc: Alexander Shiyan 
Cc: Baruch Siach 
Cc: Maciej W. Rozycki 
Cc: Shawn Guo 
Cc: Sascha Hauer 
Cc: Fabio Estevam 
Cc: Neil Armstrong 
Cc: Kevin Hilman 
Cc: Jerome Brunet 
Cc: Martin Blumenstingl 
Cc: Taichi Sugaya 
Cc: Takao Orito 
Cc: Bjorn Andersson 
Cc: Konrad Dybcio 
Cc: Pali Rohár 
Cc: Michael Ellerman 
Cc: Nicholas Piggin 
Cc: Christophe Leroy 
Cc: Aneesh Kumar K.V 
Cc: Naveen N. Rao 
Cc: Manivannan Sadhasivam 
Cc: Krzysztof Kozlowski 
Cc: Alim Akhtar 
Cc: Laxman Dewangan 
Cc: Thierry Reding 
Cc: Jonathan Hunter 
Cc: Orson Zhai 
Cc: Baolin Wang 
Cc: Chunyan Zhang 
Cc: Patrice Chotard 
Cc: Maxime Coquelin 
Cc: Alexandre Torgue 
Cc: David S. Miller 
Cc: Hammer Hsieh 
Cc: Peter Korsgaard 
Cc: Timur Tabi 
Cc: Michal Simek 
Cc: Sumit Semwal 
Cc: Christian König 
Link: https://lore.kernel.org/r/20240405060826.2521-13-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: port: Introduce a common helper to read properties

2024-03-05T13:38:28+00:00

Several serial drivers want to read the same or similar set of
the port properties. Make a common helper for them.

Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20240304123035.758700-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: core: Add UPIO_UNKNOWN constant for unknown port type

2024-03-05T13:38:28+00:00

In some APIs we would like to assign the special value to iotype
and compare against it in another places. Introduce UPIO_UNKNOWN
for this purpose.

Note, we can't use 0, because it's a valid value for IO port access.

Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20240304123035.758700-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: core: Move struct uart_port::quirks closer to possible values

2024-03-05T13:38:28+00:00

Currently it's not crystal clear what UPIO_* and UPQ_* definitions
belong to. Reindent the code, so it will be easy to read and understand.
No functional changes intended.

Reviewed-by: Andi Shyti 
Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20240304123035.758700-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: core: only stop transmit when HW fifo is empty

2024-03-05T13:37:29+00:00

If the circular buffer is empty, it just means we fit all characters to
send into the HW fifo, but not that the hardware finished transmitting
them.

So if we immediately call stop_tx() after that, this may abort any
pending characters in the HW fifo, and cause dropped characters on the
console.

Fix this by only stopping tx when the tx HW fifo is actually empty.

Fixes: 8275b48b2780 ("tty: serial: introduce transmit helpers")
Cc: stable@vger.kernel.org
Signed-off-by: Jonas Gorski 
Link: https://lore.kernel.org/r/20240303150807.68117-1-jonas.gorski@gmail.com
Signed-off-by: Greg Kroah-Hartman

serial: core: introduce uart_port_tx_flags()

2024-02-06T14:42:02+00:00

And an enum with a flag: UART_TX_NOSTOP. To NOT call
__port->ops->stop_tx() when the circular buffer is empty. mxs-uart needs
this (see the next patch).

Signed-off-by: "Jiri Slaby (SUSE)" 
Cc: stable 
Tested-by: Emil Kronborg 
Link: https://lore.kernel.org/r/20240201105557.28043-1-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: core: Update uart_poll_timeout() function to return unsigned long

2024-01-04T15:20:05+00:00

The function uart_fifo_timeout() returns an unsigned long value, which
is the number of jiffies. Therefore, change the variable timeout in the
function uart_poll_timeout() from int to unsigned long.
Change the return type of the function uart_poll_timeout() from int to
unsigned long to be consistent with the type of timeout values.

Signed-off-by: Vamshi Gajjela 
Link: https://lore.kernel.org/r/20231109063417.3971005-2-vamshigajjela@google.com
Signed-off-by: Greg Kroah-Hartman

serial: core: fix kernel-doc for uart_port_unlock_irqrestore()

2023-10-03T12:35:53+00:00

Fix the function name to avoid a kernel-doc warning:

include/linux/serial_core.h:666: warning: expecting prototype for uart_port_lock_irqrestore(). Prototype was for uart_port_unlock_irqrestore() instead

Fixes: b0af4bcb4946 ("serial: core: Provide port lock wrappers")
Signed-off-by: Randy Dunlap 
Cc: Thomas Gleixner 
Cc: John Ogness 
Cc: linux-serial@vger.kernel.org
Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Reviewed-by: John Ogness 
Link: https://lore.kernel.org/r/20230927044128.4748-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman

serial: core: Use lock wrappers

2023-09-18T09:18:08+00:00

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 
Reviewed-by: Ilpo Järvinen 
Signed-off-by: John Ogness 
Link: https://lore.kernel.org/r/20230914183831.587273-3-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman

serial: core: Provide port lock wrappers

2023-09-18T09:18:08+00:00

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.

Provide wrapper functions for spin_[un]lock*(port->lock) invocations so
that the console mechanics can be applied later on at a single place and
does not require to copy the same logic all over the drivers.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ilpo Järvinen 
Signed-off-by: John Ogness 
Link: https://lore.kernel.org/r/20230914183831.587273-2-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman