ACPI: SPCR: Make SPCR available to x86

SPCR is currently only enabled or ARM64 and x86 can use SPCR to setup
an early console.

General fixes include updating Documentation & Kconfig (for x86),
updating comments, and changing parse_spcr() to acpi_parse_spcr(),
and earlycon_init_is_deferred to earlycon_acpi_spcr_enable to be
more descriptive.

On x86, many systems have a valid SPCR table but the table version is
not 2 so the table version check must be a warning.

On ARM64 when the kernel parameter earlycon is used both the early console
and console are enabled.  On x86, only the earlycon should be enabled by
by default.  Modify acpi_parse_spcr() to allow options for initializing
the early console and console separately.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Mark Salter <msalter@redhat.com>
Tested-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 21 insertions, 15 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 46505396869e..ddcb5f40e8ee 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -79,7 +79,12 @@ config ACPI_DEBUGGER_USER
 endif
 
 config ACPI_SPCR_TABLE
-	bool
+	bool "ACPI Serial Port Console Redirection Support"
+	default y if X86
+	help
+	  Enable support for Serial Port Console Redirection (SPCR) Table.
+	  This table provides information about the configuration of the
+	  earlycon console.
 
 config ACPI_LPIT
 	bool
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 324b35bfe781..89e97d21a89c 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -21,7 +21,7 @@
  * occasionally getting stuck as 1. To avoid the potential for a hang, check
  * TXFE == 0 instead of BUSY == 1. This may not be suitable for all UART
  * implementations, so only do so if an affected platform is detected in
- * parse_spcr().
+ * acpi_parse_spcr().
  */
 bool qdf2400_e44_present;
 EXPORT_SYMBOL(qdf2400_e44_present);
@@ -74,19 +74,21 @@ static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
 }
 
 /**
- * parse_spcr() - parse ACPI SPCR table and add preferred console
+ * acpi_parse_spcr() - parse ACPI SPCR table and add preferred console
  *
- * @earlycon: set up earlycon for the console specified by the table
+ * @enable_earlycon: set up earlycon for the console specified by the table
+ * @enable_console: setup the console specified by the table.
  *
  * For the architectures with support for ACPI, CONFIG_ACPI_SPCR_TABLE may be
  * defined to parse ACPI SPCR table.  As a result of the parsing preferred
- * console is registered and if @earlycon is true, earlycon is set up.
+ * console is registered and if @enable_earlycon is true, earlycon is set up.
+ * If @enable_console is true the system console is also configured.
  *
  * When CONFIG_ACPI_SPCR_TABLE is defined, this function should be called
  * from arch initialization code as soon as the DT/ACPI decision is made.
  *
  */
-int __init parse_spcr(bool earlycon)
+int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
 {
 	static char opts[64];
 	struct acpi_table_spcr *table;
@@ -105,11 +107,8 @@ int __init parse_spcr(bool earlycon)
 	if (ACPI_FAILURE(status))
 		return -ENOENT;
 
-	if (table->header.revision < 2) {
-		err = -ENOENT;
-		pr_err("wrong table version\n");
-		goto done;
-	}
+	if (table->header.revision < 2)
+		pr_info("SPCR table version %d\n", table->header.revision);
 
 	if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
 		switch (ACPI_ACCESS_BIT_WIDTH((
@@ -185,7 +184,7 @@ int __init parse_spcr(bool earlycon)
 	 */
 	if (qdf2400_erratum_44_present(&table->header)) {
 		qdf2400_e44_present = true;
-		if (earlycon)
+		if (enable_earlycon)
 			uart = "qdf2400_e44";
 	}
 
@@ -205,11 +204,13 @@ int __init parse_spcr(bool earlycon)
 
 	pr_info("console: %s\n", opts);
 
-	if (earlycon)
+	if (enable_earlycon)
 		setup_earlycon(opts);
 
-	err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);
-
+	if (enable_console)
+		err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);
+	else
+		err = 0;
 done:
 	acpi_put_table((struct acpi_table_header *)table);
 	return err;