kernel/linux.git/drivers/tty, branch v6.6.132

serial: uartlite: fix PM runtime usage count underflow on probe

2026-03-25T10:06:04+00:00

commit d54801cd509515f674a5aac1d3ea1401d2a05863 upstream. ulite_probe() calls pm_runtime_put_autosuspend() at the end of probe without holding a corresponding PM runtime reference for non-console ports. During ulite_assign(), uart_add_one_port() triggers uart_configure_port() which calls ulite_pm() via uart_change_pm(). For non-console ports, the UART core performs a balanced get/put cycle: uart_change_pm(ON) -> ulite_pm() -> pm_runtime_get_sync() +1 uart_change_pm(OFF) -> ulite_pm() -> pm_runtime_put_autosuspend() -1 This leaves no spare reference for the pm_runtime_put_autosuspend() at the end of probe. The PM runtime core prevents the count from actually going below zero, and instead triggers a "Runtime PM usage count underflow!" warning. For console ports the bug is masked: the UART core skips the uart_change_pm(OFF) call, so the UART core's unbalanced get happens to pair with probe's trailing put. Add pm_runtime_get_noresume() before pm_runtime_enable() to take an explicit probe-owned reference that the trailing pm_runtime_put_autosuspend() can release. This ensures a correct usage count regardless of whether the port is a console. Fixes: 5bbe10a6942d ("tty: serial: uartlite: Add runtime pm support") Cc: stable Signed-off-by: Maciej Andrzejewski ICEYE Link: https://patch.msgid.link/20260305123746.4152800-1-maciej.andrzejewski@m-works.net Signed-off-by: Greg Kroah-Hartman

serial: 8250: Add late synchronize_irq() to shutdown to handle DW UART BUSY

2026-03-25T10:06:04+00:00

commit e0a368ae79531ff92105a2692f10d83052055856 upstream. When DW UART is !uart_16550_compatible, it can indicate BUSY at any point (when under constant Rx pressure) unless a complex sequence of steps is performed. Any LCR write can run a foul with the condition that prevents writing LCR while the UART is BUSY, which triggers BUSY_DETECT interrupt that seems unmaskable using IER bits. Normal flow is that dw8250_handle_irq() handles BUSY_DETECT condition by reading USR register. This BUSY feature, however, breaks the assumptions made in serial8250_do_shutdown(), which runs synchronize_irq() after clearing IER and assumes no interrupts can occur after that point but then proceeds to update LCR, which on DW UART can trigger an interrupt. If serial8250_do_shutdown() releases the interrupt handler before the handler has run and processed the BUSY_DETECT condition by read the USR register, the IRQ is not deasserted resulting in interrupt storm that triggers "irq x: nobody cared" warning leading to disabling the IRQ. Add late synchronize_irq() into serial8250_do_shutdown() to ensure BUSY_DETECT from DW UART is handled before port's interrupt handler is released. Alternative would be to add DW UART specific shutdown function but it would mostly duplicate the generic code and the extra synchronize_irq() seems pretty harmless in serial8250_do_shutdown(). Fixes: 7d4008ebb1c9 ("tty: add a DesignWare 8250 driver") Cc: stable Reported-by: Bandal, Shankar Tested-by: Bandal, Shankar Tested-by: Murthy, Shanth Reviewed-by: Andy Shevchenko Signed-off-by: Ilpo Järvinen Link: https://patch.msgid.link/20260203171049.4353-7-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

serial: 8250: Fix TX deadlock when using DMA

2026-03-25T10:06:04+00:00

commit a424a34b8faddf97b5af41689087e7a230f79ba7 upstream. `dmaengine_terminate_async` does not guarantee that the `__dma_tx_complete` callback will run. The callback is currently the only place where `dma->tx_running` gets cleared. If the transaction is canceled and the callback never runs, then `dma->tx_running` will never get cleared and we will never schedule new TX DMA transactions again. This change makes it so we clear `dma->tx_running` after we terminate the DMA transaction. This is "safe" because `serial8250_tx_dma_flush` is holding the UART port lock. The first thing the callback does is also grab the UART port lock, so access to `dma->tx_running` is serialized. Fixes: 9e512eaaf8f4 ("serial: 8250: Fix fifo underflow on flush") Cc: stable Signed-off-by: Raul E Rangel Link: https://patch.msgid.link/20260209135815.1.I16366ecb0f62f3c96fe3dd5763fcf6f3c2b4d8cd@changeid Signed-off-by: Greg Kroah-Hartman

serial: 8250_pci: add support for the AX99100

2026-03-25T10:06:04+00:00

commit 9c0072bc33d349c83d223e64be30794e11938a6b upstream. This is found in popular brands such as StarTech.com or Delock, and has been a source of frustration to quite a few people, if I can trust Amazon comments complaining about Linux support via the official out-of-the-tree driver. Signed-off-by: Martin Roukala (né Peres) Cc: stable Link: https://patch.msgid.link/20260309-8250_pci_ax99100-v1-1-3328bdfd8e94@mupuf.org Signed-off-by: Greg Kroah-Hartman

serial: 8250: 8250_omap.c: Clear DMA RX running status only after DMA termination is done

2026-03-04T12:20:54+00:00

[ Upstream commit a5fd8945a478ff9be14812693891d7c9b4185a50 ] Clear rx_running flag only after DMA teardown polling completes. In the previous implementation the flag was being cleared while hardware teardown was still in progress, creating a mismatch between software state (flag = 0, "ready") and hardware state (still terminating). Signed-off-by: Moteen Shah Link: https://patch.msgid.link/20260112081829.63049-3-m-shah@ti.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: 8250_dw: handle clock enable errors in runtime_resume

2026-03-04T12:20:53+00:00

[ Upstream commit d31228143a489ba6ba797896a07541ce06828c09 ] Add error checking for clk_prepare_enable() calls in dw8250_runtime_resume(). Currently if either clock fails to enable, the function returns success while leaving clocks in inconsistent state. This change implements comprehensive error handling by checking the return values of both clk_prepare_enable() calls. If the second clock enable operation fails after the first clock has already been successfully enabled, the code now properly cleans up by disabling and unpreparing the first clock before returning. The error code is then propagated to the caller, ensuring that clock enable failures are properly reported rather than being silently ignored. Signed-off-by: Artem Shimko Link: https://patch.msgid.link/20251104145433.2316165-2-a.shimko.dev@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: SH_SCI: improve "DMA support" prompt

2026-03-04T12:20:09+00:00

[ Upstream commit 93bb95a11238d66a4c9aa6eabf9774b073a5895c ] Having a prompt of "DMA support" suddenly appear during a "make oldconfig" can be confusing. Add a little helpful text to the prompt message. Fixes: 73a19e4c0301 ("serial: sh-sci: Add DMA support.") Signed-off-by: Randy Dunlap Reviewed-by: Geert Uytterhoeven Link: https://patch.msgid.link/20260110232643.3533351-5-rdunlap@infradead.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: imx: change SERIAL_IMX_CONSOLE to bool

2026-03-04T12:20:09+00:00

[ Upstream commit 79527d86ba91c2d9354832d19fd12b3baa66bd10 ] SERIAL_IMX_CONSOLE is a build option for the imx driver (SERIAL_IMX). It does not build a separate console driver file, so it can't be built as a module since it isn't built at all. Change the Kconfig symbol from tristate to bool and update the help text accordingly. Fixes: 0db4f9b91c86 ("tty: serial: imx: enable imx serial console port as module") Signed-off-by: Randy Dunlap Link: https://patch.msgid.link/20260110232643.3533351-2-rdunlap@infradead.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: 8250_pci: Fix broken RS485 for F81504/508/512

2026-01-30T09:27:34+00:00

commit 27aff0a56b3c77ea1a73641c9b3c4172a8f7238f upstream. Fintek F81504/508/512 can support both RTS_ON_SEND and RTS_AFTER_SEND, but pci_fintek_rs485_supported only announces the former. This makes it impossible to unset SER_RS485_RTS_ON_SEND from userspace because of uart_sanitize_serial_rs485(). Some devices with these chips need RTS low on TX, so they are effectively broken. Fix this by announcing the support for SER_RS485_RTS_AFTER_SEND, similar to commit 068d35a7be65 ("serial: sc16is7xx: announce support for SER_RS485_RTS_ON_SEND"). Fixes: 4afeced55baa ("serial: core: fix sanitizing check for RTS settings") Cc: stable Signed-off-by: Marnix Rijnart Link: https://patch.msgid.link/20260112000931.61703-1-marnix.rijnart@iwell.eu Signed-off-by: Greg Kroah-Hartman

tty: fix tty_port_tty_*hangup() kernel-doc

2026-01-11T14:22:33+00:00

commit 6241b49540a65a6d5274fa938fd3eb4cbfe2e076 upstream. The commit below added a new helper, but omitted to move (and add) the corressponding kernel-doc. Do it now. Signed-off-by: "Jiri Slaby (SUSE)" Fixes: 2b5eac0f8c6e ("tty: introduce and use tty_port_tty_vhangup() helper") Link: https://lore.kernel.org/all/b23d566c-09dc-7374-cc87-0ad4660e8b2e@linux.intel.com/ Reported-by: Ilpo Järvinen Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Link: https://lore.kernel.org/r/20250624080641.509959-6-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman