6.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chen Pei cp0613@linux.alibaba.com
[ Upstream commit 4d330fe54145ecfbb657ac01a554fdedf3c1927e ]
The Microsoft Serial Port Console Redirection (SPCR) specification revision 1.09 comprises additional field: Precise Baud Rate [1].
It is used to describe non-traditional baud rates (such as those used by high-speed UARTs).
It contains a specific non-zero baud rate which overrides the value of the Configured Baud Rate field. If this field is zero or not present, Configured Baud Rate is used.
Link: https://learn.microsoft.com/en-us/windows-hardware/drivers/serports/serial-p... [1] Signed-off-by: Chen Pei cp0613@linux.alibaba.com Link: https://patch.msgid.link/20250913070815.16758-1-cp0613@linux.alibaba.com [ rjw: Corrected typo in the subject ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/spcr.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c index cd36a97b0ea2c..fa12e740386de 100644 --- a/drivers/acpi/spcr.c +++ b/drivers/acpi/spcr.c @@ -146,7 +146,15 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console) goto done; }
- switch (table->baud_rate) { + /* + * SPCR 1.09 defines Precise Baud Rate Filed contains a specific + * non-zero baud rate which overrides the value of the Configured + * Baud Rate field. If this field is zero or not present, Configured + * Baud Rate is used. + */ + if (table->precise_baudrate) + baud_rate = table->precise_baudrate; + else switch (table->baud_rate) { case 0: /* * SPCR 1.04 defines 0 as a preconfigured state of UART.