| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.20 077/352] ACPI: SPCR: Consider baud rate 0 as preconfigured state | Date | Mon, 11 Feb 2019 15:15:04 +0100 |
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4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit b413b1abeb21b4a152c0bf8d1379efa30759b6e3 ]
Since SPCR 1.04 [1] the baud rate of 0 means a preconfigured state of UART. Assume firmware or bootloader configures console correctly.
[1]: https://docs.microsoft.com/en-us/windows-hardware/drivers/serports/serial-port-console-redirection-table
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Prarit Bhargava <prarit@redhat.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/acpi/spcr.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c index 9d52743080a4..c336784d0bcb 100644 --- a/drivers/acpi/spcr.c +++ b/drivers/acpi/spcr.c @@ -148,6 +148,13 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console) } switch (table->baud_rate) { + case 0: + /* + * SPCR 1.04 defines 0 as a preconfigured state of UART. + * Assume firmware or bootloader configures console correctly. + */ + baud_rate = 0; + break; case 3: baud_rate = 9600; break; @@ -196,6 +203,10 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console) * UART so don't attempt to change to the baud rate state * in the table because driver cannot calculate the dividers */ + baud_rate = 0; + } + + if (!baud_rate) { snprintf(opts, sizeof(opts), "%s,%s,0x%llx", uart, iotype, table->serial_port.address); } else { -- 2.19.1
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