linux-stable.git/drivers/tty/serial/sh-sci.c, branch linux-6.10.y

serial: sh-sci: simplify locking when re-issuing RXDMA fails

2024-05-10T10:48:33+00:00

Avoid a superfluous unlock/lock-pair by simply moving the printout to
the end of bailing out.

Signed-off-by: Wolfram Sang 
Link: https://lore.kernel.org/r/20240506114016.30498-10-wsa+renesas@sang-engineering.com
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: let timeout timer only run when DMA is scheduled

2024-05-10T10:48:33+00:00

The hrtimer for RXDMA timeout was unconditionally restarted in the RXDMA
complete handler ignoring the fact that setting up DMA may fail and PIO
is used instead. Explicitly stop the timer when DMA is completed and
only restart it when setting up DMA was successful. This makes the
intention of the timer much clearer, the driver easier to understand and
simplifies assumptions about the timer. The latter avoids race
conditions if these assumptions were not met or confused.

Signed-off-by: Wolfram Sang 
Link: https://lore.kernel.org/r/20240506114016.30498-9-wsa+renesas@sang-engineering.com
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: describe locking requirements for invalidating RXDMA

2024-05-10T10:48:33+00:00

Make sure everyone knows that calling this function needs protection.

Signed-off-by: Wolfram Sang 
Link: https://lore.kernel.org/r/20240506114016.30498-8-wsa+renesas@sang-engineering.com
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: protect invalidating RXDMA on shutdown

2024-05-10T10:48:33+00:00

The to-be-fixed commit removed locking when invalidating the DMA RX
descriptors on shutdown. It overlooked that there is still a rx_timer
running which may still access the protected data. So, re-add the
locking.

Reported-by: Dirk Behme 
Closes: https://lore.kernel.org/r/ee6c9e16-9f29-450e-81da-4a8dceaa8fc7@de.bosch.com
Fixes: 2c4ee23530ff ("serial: sh-sci: Postpone DMA release when falling back to PIO")
Signed-off-by: Wolfram Sang 
Link: https://lore.kernel.org/r/20240506114016.30498-7-wsa+renesas@sang-engineering.com
Signed-off-by: Greg Kroah-Hartman

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: sh-sci: Call sci_serial_{in,out}() directly

2024-03-05T13:37:32+00:00

Unlike the 8250 serial driver complex, the sh-sci driver uses only a
single pair of functions to read and write serial port registers.
Hence there is no need to incur the overhead of calling them through
indirection, like the serial_port_{in,out}() wrappers do.

Replace all calls to these wrappers by direct calls to
sci_serial_{in,out}().

Remove the setup of the uart_port.serial_{in,out}() callbacks.  After
removal of all calls to serial_port_{in,out}() in the sh-sci driver, the
only remaining user is uart_xchar_out(), which the sh-sci driver does
not use.

Signed-off-by: Geert Uytterhoeven 
Acked-by: John Paul Adrian Glaubitz 
Link: https://lore.kernel.org/r/51e79d601cb9d9d63822d3773d3cf05a96868612.1709548811.git.geert+renesas@glider.be
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: convert not to use dma_request_slave_channel()

2023-11-23T19:33:03+00:00

dma_request_slave_channel() is deprecated. dma_request_chan() should
be used directly instead.

Switch to the preferred function and update the error handling accordingly.

Signed-off-by: Christophe JAILLET 
Link: https://lore.kernel.org/r/d6773b9bd88dbbbea06bc6d5cd59aa117b1ee2ee.1700416841.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Convert to platform remove callback returning void

2023-11-23T19:12:34+00:00

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 
Reviewed-by: Geert Uytterhoeven 
Link: https://lore.kernel.org/r/20231110152927.70601-39-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Use port lock wrappers

2023-09-18T09:18:15+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 
Signed-off-by: John Ogness 
Link: https://lore.kernel.org/r/20230914183831.587273-61-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman

Merge 6.5-rc4 into tty-next

2023-07-31T07:39:56+00:00

We need the serial/tty fixes in here as well for testing and future
development.

Signed-off-by: Greg Kroah-Hartman