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| author | Chen Pei <cp0613@linux.alibaba.com> | 2025-09-13 15:08:15 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-11-13 15:34:07 -0500 |
| commit | c9172cced19bf2a84f3563817076326e71e7cca3 (patch) | |
| tree | 59c9d913848cba65fc3343b160e33f11e17b5343 /drivers/acpi | |
| parent | f25411c9d87bdc8a35eecfbac525a081677470ff (diff) | |
| download | linux-c9172cced19bf2a84f3563817076326e71e7cca3.tar.gz linux-c9172cced19bf2a84f3563817076326e71e7cca3.tar.bz2 linux-c9172cced19bf2a84f3563817076326e71e7cca3.zip | |
ACPI: SPCR: Support Precise Baud Rate field
[ 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-port-console-redirection-table [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>
Diffstat (limited to 'drivers/acpi')
| -rw-r--r-- | drivers/acpi/spcr.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c index cd36a97b0ea2..fa12e740386d 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. |