From 98036fbdaf0ac1d6dc3ab3cb6db24c020bb65d6f Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Thu, 27 Feb 2020 17:21:56 +0200 Subject: [PATCH] x86: acpi: Let OS know that console already had been initialized 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 Reviewed-by: Bin Meng --- arch/x86/lib/acpi_table.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/lib/acpi_table.c b/arch/x86/lib/acpi_table.c index 66e32f2..074987e 100644 --- a/arch/x86/lib/acpi_table.c +++ b/arch/x86/lib/acpi_table.c @@ -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); } -- 2.7.4