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x86: acpi: Let OS know that console already had been initialized

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SPCR has no clue if the UART base clock speed is different to
the default one. However, the SPCR 1.04 defines baud rate 0 as
a preconfigured state of UART and OS is supposed not to touch
the configuration of the serial device.

Linux kernel supports that starting from v5.0, see commit
b413b1abeb21 ("ACPI: SPCR: Consider baud rate 0 as preconfigured state")
for the details.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Andy Shevchenko 2020-02-27 17:21:56 +02:00 committed by Bin Meng
parent 5db92a0e96
commit 98036fbdaf
1 changed files with 9 additions and 0 deletions
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9
arch/x86/lib/acpi_table.c
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@ -471,6 +471,15 @@ static void acpi_create_spcr(struct acpi_spcr *spcr)
spcr->pci_device_id = 0xffff;
spcr->pci_vendor_id = 0xffff;
/*
* SPCR has no clue if the UART base clock speed is different
* to the default one. However, the SPCR 1.04 defines baud rate
* 0 as a preconfigured state of UART and OS is supposed not
* to touch the configuration of the serial device.
*/
if (serial_info.clock != SERIAL_DEFAULT_CLOCK)
spcr->baud_rate = 0;
/* Fix checksum */
header->checksum = table_compute_checksum((void *)spcr, header->length);
}