kernel/drivers/tty/serial/imx.c, branch linux-6.9.y

serial: imx: ensure RTS signal is not left active after shutdown

2024-07-18T11:22:50Z

commit 1af2156e58f3af1216ce2f0456b3b8949faa5c7e upstream. If a process is killed while writing to a /dev/ttymxc* device in RS485 mode, we observe that the RTS signal is left high, thus making it impossible for other devices to transmit anything. Moreover, the ->tx_state variable is left in state SEND, which means that when one next opens the device and configures baud rate etc., the initialization code in imx_uart_set_termios dutifully ensures the RTS pin is pulled down, but since ->tx_state is already SEND, the logic in imx_uart_start_tx() does not in fact pull the pin high before transmitting, so nothing actually gets on the wire on the other side of the transceiver. Only when that transmission is allowed to complete is the state machine then back in a consistent state. This is completely reproducible by doing something as simple as seq 10000 > /dev/ttymxc0 and hitting ctrl-C, and watching with a logic analyzer. Signed-off-by: Rasmus Villemoes Cc: stable Reviewed-by: Marek Vasut Link: https://lore.kernel.org/r/20240625184206.508837-1-linux@rasmusvillemoes.dk Signed-off-by: Greg Kroah-Hartman

serial: imx: Raise TX trigger level to 8

2024-07-11T10:51:05Z

[ Upstream commit a3d8728ab079951741efa11360df43dbfacba7ab ] At the default TX trigger level of 2 in non-DMA mode (meaning that an interrupt is generated when less than 2 characters are left in the FIFO), we have observed frequent buffer underruns at 115200 Baud on an i.MX8M Nano. This can cause communication issues if the receiving side expects a continuous transfer. Increasing the level to 8 makes the UART trigger an interrupt earlier, giving the kernel enough time to refill the FIFO, at the cost of triggering one interrupt per ~24 instead of ~30 bytes of transmitted data (as the i.MX UART has a 32 byte FIFO). Signed-off-by: Michael Krummsdorf Signed-off-by: Matthias Schiffer Link: https://lore.kernel.org/r/20240508133744.35858-1-matthias.schiffer@ew.tq-group.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: imx: only set receiver level if it is zero

2024-07-05T07:38:20Z

commit 9706fc87b4cff0ac4f5d5d62327be83fe72e3108 upstream. With commit a81dbd0463ec ("serial: imx: set receiver level before starting uart") we set the receiver level to its default value. This caused a regression when using SDMA, where the receiver level is 9 instead of 8 (default). This change will first check if the receiver level is zero and only then set it to the default. This still avoids the interrupt storm when the receiver level is zero. Fixes: a81dbd0463ec ("serial: imx: set receiver level before starting uart") Cc: stable Signed-off-by: Stefan Eichenberger Link: https://lore.kernel.org/r/20240703112543.148304-1-eichest@gmail.com Signed-off-by: Greg Kroah-Hartman

serial: imx: set receiver level before starting uart

2024-07-05T07:38:10Z

commit a81dbd0463eca317eee44985a66aa6cc2ce5c101 upstream. Set the receiver level to something > 0 before calling imx_uart_start_rx in rs485_config. This is necessary to avoid an interrupt storm that might prevent the system from booting. This was seen on an i.MX7 device when the rs485-rts-active-low property was active in the device tree. Fixes: 6d215f83e5fc ("serial: imx: warn user when using unsupported configuration") Cc: stable Signed-off-by: Stefan Eichenberger Link: https://lore.kernel.org/r/20240621153829.183780-1-eichest@gmail.com Signed-off-by: Greg Kroah-Hartman

serial: imx: Introduce timeout when waiting on transmitter empty

2024-06-27T11:52:18Z

[ Upstream commit e533e4c62e9993e62e947ae9bbec34e4c7ae81c2 ] By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential deadlock. In case of the timeout, there is not much we can do, so we simply ignore the transmitter state and optimistically try to continue. Signed-off-by: Esben Haabendal Acked-by: Marc Kleine-Budde Link: https://lore.kernel.org/r/919647898c337a46604edcabaf13d42d80c0915d.1712837613.git.esben@geanix.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

tty: serial: imx: Fix broken RS485

2024-03-02T21:10:35Z

When about to transmit the function imx_uart_start_tx is called and in some RS485 configurations this function will call imx_uart_stop_rx. The problem is that imx_uart_stop_rx will enable loopback in order to release the RS485 bus, but when loopback is enabled transmitted data will just be looped to RX. This patch fixes the above problem by not enabling loopback when about to transmit. This driver now works well when used for RS485 half duplex master configurations. Fixes: 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high") Cc: stable Signed-off-by: Rickard x Andersson Tested-by: Christoph Niedermaier Link: https://lore.kernel.org/r/20240221115304.509811-1-rickaran@axis.com Signed-off-by: Greg Kroah-Hartman

serial: core, imx: do not set RS485 enabled if it is not supported

2024-01-04T15:29:51Z

If the imx driver cannot support RS485 it nullifies the ports rs485_supported structure. But it still calls uart_get_rs485_mode() which may set the RS485_ENABLED flag nevertheless. This may lead to an attempt to configure RS485 even if it is not supported when the flag is evaluated in uart_configure_port() at port startup. Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED flag is not supported by the caller. With this fix a check for RTS availability is now obsolete in the imx driver, since it can not evaluate to true any more. So remove this check. Furthermore the explicit nullifcation of rs485_supported is not needed, since the memory has already been set to zeros at allocation. So remove this, too. Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported") Cc: Shawn Guo Cc: Sascha Hauer Cc: Suggested-by: Uwe Kleine-König Signed-off-by: Lino Sanfilippo Reviewed-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20240103061818.564-6-l.sanfilippo@kunbus.com Signed-off-by: Greg Kroah-Hartman

serial: Do not hold the port lock when setting rx-during-tx GPIO

2024-01-04T15:26:09Z

Both the imx and stm32 driver set the rx-during-tx GPIO in rs485_config(). Since this function is called with the port lock held, this can be a problem in case that setting the GPIO line can sleep (e.g. if a GPIO expander is used which is connected via SPI or I2C). Avoid this issue by moving the GPIO setting outside of the port lock into the serial core and thus making it a generic feature. Also with commit c54d48543689 ("serial: stm32: Add support for rs485 RX_DURING_TX output GPIO") the SER_RS485_RX_DURING_TX flag is only set if a rx-during-tx GPIO is _not_ available, which is wrong. Fix this, too. Furthermore reset old GPIO settings in case that changing the RS485 configuration failed. Fixes: c54d48543689 ("serial: stm32: Add support for rs485 RX_DURING_TX output GPIO") Fixes: ca530cfa968c ("serial: imx: Add support for RS485 RX_DURING_TX output GPIO") Cc: Shawn Guo Cc: Sascha Hauer Cc: Signed-off-by: Lino Sanfilippo Link: https://lore.kernel.org/r/20240103061818.564-2-l.sanfilippo@kunbus.com Signed-off-by: Greg Kroah-Hartman

serial: imx: Ensure that imx_uart_rs485_config() is called with enabled clock

2024-01-04T15:21:30Z

There are register accesses in the function imx_uart_rs485_config(). The clock must be enabled for these accesses. This was ensured by calling it via the function uart_rs485_config() in the probe() function within the range where the clock is enabled. With the commit 7c7f9bc986e6 ("serial: Deassert Transmit Enable on probe in driver-specific way") it was removed from the probe() function and is now only called through the function uart_add_one_port() which is located at the end of the probe() function. But the clock is already switched off in this area. To ensure that the clock is enabled during register access, move the disabling of the clock to the very end of the probe() function. To avoid leaking enabled clocks on error also add an error path for exiting with disabling the clock. Fixes: 7c7f9bc986e6 ("serial: Deassert Transmit Enable on probe in driver-specific way") Cc: stable Signed-off-by: Christoph Niedermaier Reviewed-by: Lukas Wunner Link: https://lore.kernel.org/r/20231226113647.39376-1-cniedermaier@dh-electronics.com Signed-off-by: Greg Kroah-Hartman

serial: imx: Correct clock error message in function probe()

2024-01-04T15:20:56Z

Correct the clock error message by changing the clock name. Fixes: 1e512d45332b ("serial: imx: add error messages when .probe fails") Signed-off-by: Christoph Niedermaier Reviewed-by: Uwe Kleine-König Link: https://lore.kernel.org/r/20231224093209.2612-1-cniedermaier@dh-electronics.com Signed-off-by: Greg Kroah-Hartman