Date: Fri, 17 Apr 2026 19:37:40 +0000 From: Roger Pau =?utf-8?Q?Monn=C3=A9?= <royger@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 45c8ddc874bb - main - uart/pci: recover ADL AMT device after FIFO size probing Message-ID: <69e28c04.1bb57.42d4783d@gitrepo.freebsd.org>
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The branch main has been updated by royger: URL: https://cgit.FreeBSD.org/src/commit/?id=45c8ddc874bb9149ed20cb46b6ef8bdd0567714c commit 45c8ddc874bb9149ed20cb46b6ef8bdd0567714c Author: Roger Pau Monné <royger@FreeBSD.org> AuthorDate: 2026-03-27 09:55:02 +0000 Commit: Roger Pau Monné <royger@FreeBSD.org> CommitDate: 2026-04-17 19:37:26 +0000 uart/pci: recover ADL AMT device after FIFO size probing When the Alder Lake Serial-over-LAN device is put into loopback mode and repeated writes are performed to the data register it results in the device ending up in a non-functional state afterwards. Recovering the device to a working state requires re-writing the LCR register with it's current value (no effective change). This should be harmless on all other devices. Sponsored by: Citrix Systems R&D Differential revision: https://reviews.freebsd.org/D56107 Reviewed by: imp --- sys/dev/uart/uart_dev_ns8250.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/sys/dev/uart/uart_dev_ns8250.c b/sys/dev/uart/uart_dev_ns8250.c index b0c7cd4b44e1..c13eabe9055e 100644 --- a/sys/dev/uart/uart_dev_ns8250.c +++ b/sys/dev/uart/uart_dev_ns8250.c @@ -999,6 +999,15 @@ ns8250_bus_probe(struct uart_softc *sc) uart_setreg(bas, REG_IER, ier); uart_setreg(bas, REG_MCR, mcr); uart_setreg(bas, REG_FCR, 0); + /* + * The Alder Lake AMT SOL Redirection device will never + * set LSR_OE (when in loopback mode at least) and + * instead block further input by not setting LSR_TEMT. + * Recovering the device afterwards into a working + * state requires re-writing the LCR register. This + * should be harmless on all other devices. + */ + uart_setreg(bas, REG_LCR, uart_getreg(bas, REG_LCR)); uart_barrier(bas); count = 0; goto describe;home | help
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