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Message-ID: <20240912113616.3.I1b7a5033a2191cb0cdbadc2d51666a97f16cc663@changeid>
Date: Thu, 12 Sep 2024 11:36:21 -0600
From: Raul E Rangel <rrangel@...omium.org>
To: linux-serial@...r.kernel.org
Cc: pmladek@...e.com,
rafael.j.wysocki@...el.com,
ribalda@...omium.org,
Raul E Rangel <rrangel@...omium.org>,
Len Brown <lenb@...nel.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Robert Moore <robert.moore@...el.com>,
acpica-devel@...ts.linux.dev,
linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] ACPI: SPCR: Add support for rev 3
Revision 3 supports specifying the UART input clock. This allows for
proper computation of the UART divisor when the baud rate is specified.
The earlycon code can accept the following format (See `parse_options`
in `earlycon.c`.):
* <name>,io|mmio|mmio32|mmio32be,<addr>,<baud>,<uartclk>,<options>
This change makes it so the uartclk is passed along if it's defined in
the SPCR table.
Booting with `earlycon` and a SPCR v3 table that has the uartclk and
baud defined:
[ 0.028251] ACPI: SPCR: console: uart,mmio32,0xfedc9000,115200,48000000
[ 0.028267] earlycon: uart0 at MMIO32 0x00000000fedc9000 (options '115200,48000000')
[ 0.028272] printk: legacy bootconsole [uart0] enabled
Link: https://learn.microsoft.com/en-us/windows-hardware/drivers/serports/serial-port-console-redirection-table
Signed-off-by: Raul E Rangel <rrangel@...omium.org>
---
drivers/acpi/spcr.c | 5 ++++-
include/acpi/actbl3.h | 6 +++---
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index cd36a97b0ea2c7..67ae42afcc59ef 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -209,9 +209,12 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
if (!baud_rate) {
snprintf(opts, sizeof(opts), "%s,%s,0x%llx", uart, iotype,
table->serial_port.address);
- } else {
+ } else if (table->header.revision <= 2 || !table->uartclk) {
snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
table->serial_port.address, baud_rate);
+ } else {
+ snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d,%d", uart, iotype,
+ table->serial_port.address, baud_rate, table->uartclk);
}
pr_info("console: %s\n", opts);
diff --git a/include/acpi/actbl3.h b/include/acpi/actbl3.h
index 8f775e3a08fdfb..afe45a2379866a 100644
--- a/include/acpi/actbl3.h
+++ b/include/acpi/actbl3.h
@@ -92,10 +92,10 @@ struct acpi_table_slit {
/*******************************************************************************
*
* SPCR - Serial Port Console Redirection table
- * Version 2
+ * Version 3
*
* Conforms to "Serial Port Console Redirection Table",
- * Version 1.03, August 10, 2015
+ * Version 1.08, October 7, 2021
*
******************************************************************************/
@@ -120,7 +120,7 @@ struct acpi_table_spcr {
u8 pci_function;
u32 pci_flags;
u8 pci_segment;
- u32 reserved2;
+ u32 uartclk;
};
/* Masks for pci_flags field above */
--
2.46.0.662.g92d0881bb0-goog
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