Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Mark Salter <msalter@redhat.com>]

On Thu, 2018-01-18 at 10:09 -0500, Prarit Bhargava wrote:
> Note on testing:  I've tested this on several ARM64 and x86 boxes (only
> earlycon, console=ttyS0,115200, and with both options), verified that
> functionality on ARM64 has not changed (ie, CONFIG_ACPI_SPCR_TABLE is
> always =y), and verified functionality when !CONFIG_ACPI_SPCR_TABLE on
> x86.
> 
> P.
> 
> ----8<----
> 
> 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>
> Cc: linux-acpi@vger.kernel.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-pm@vger.kernel.org
> Cc: linux-serial@vger.kernel.org
> Cc: Bhupesh Sharma <bhsharma@redhat.com>
> Cc: Lv Zheng <lv.zheng@intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: "Rafael J. Wysocki" Mrjw@rjwysocki.net>
> Cc: Timur Tabi <timur@codeaurora.org>
> Cc: graeme.gregory@linaro.org
> Cc: mark.salter@redhat.com
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  9 +++++---
>  arch/arm64/kernel/acpi.c                        |  4 ++--
>  arch/x86/kernel/acpi/boot.c                     |  3 +++
>  drivers/acpi/Kconfig                            |  7 +++++-
>  drivers/acpi/spcr.c                             | 29 +++++++++++++------------
>  drivers/tty/serial/earlycon.c                   | 15 +++++--------
>  include/linux/acpi.h                            |  7 ++++--
>  include/linux/serial_core.h                     |  4 ++--
>  8 files changed, 44 insertions(+), 34 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 46b26bfee27b..6f519230ed34 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -915,9 +915,12 @@
>  
>  	earlycon=	[KNL] Output early console device and options.
>  
> -			When used with no options, the early console is
> -			determined by the stdout-path property in device
> -			tree's chosen node.
> +			[ARM64] The early console is determined by the
> +			stdout-path property in device tree's chosen node,
> +			or determined by the ACPI SPCR table.
> +
> +			[X86] When used with no options the early console is
> +			determined by the ACPI SPCR table.
>  
>  		cdns,<addr>[,options]
>  			Start an early, polled-mode console on a Cadence
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index b3162715ed78..2aa5609def27 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -230,10 +230,10 @@ void __init acpi_boot_table_init(void)
>  
>  done:
>  	if (acpi_disabled) {
> -		if (earlycon_init_is_deferred)
> +		if (earlycon_acpi_spcr_enable)
>  			early_init_dt_scan_chosen_stdout();
>  	} else {
> -		parse_spcr(earlycon_init_is_deferred);
> +		acpi_parse_spcr(earlycon_acpi_spcr_enable, true);
>  		if (IS_ENABLED(CONFIG_ACPI_BGRT))
>  			acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);
>  	}
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index f4c463df8b08..0bf6a58f7a6d 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -36,6 +36,7 @@
>  #include <linux/ioport.h>
>  #include <linux/pci.h>
>  #include <linux/efi-bgrt.h>
> +#include <linux/serial_core.h>
>  
>  #include <asm/e820/api.h>
>  #include <asm/irqdomain.h>
> @@ -1626,6 +1627,8 @@ int __init acpi_boot_init(void)
>  	if (!acpi_noirq)
>  		x86_init.pci.init = pci_acpi_init;
>  
> +	/* Do not enable ACPI SPCR console by default */
> +	acpi_parse_spcr(earlycon_acpi_spcr_enable, false);
>  	return 0;
>  }
>  
> 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;
> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
> index 4c8b80f1c688..870e84fb6e39 100644
> --- a/drivers/tty/serial/earlycon.c
> +++ b/drivers/tty/serial/earlycon.c
> @@ -197,25 +197,20 @@ int __init setup_earlycon(char *buf)
>  }
>  
>  /*
> - * When CONFIG_ACPI_SPCR_TABLE is defined, "earlycon" without parameters in
> - * command line does not start DT earlycon immediately, instead it defers
> - * starting it until DT/ACPI decision is made.  At that time if ACPI is enabled
> - * call parse_spcr(), else call early_init_dt_scan_chosen_stdout()
> + * This defers the initialization of the early console until after ACPI has
> + * been initialized.
>   */
> -bool earlycon_init_is_deferred __initdata;
> +bool earlycon_acpi_spcr_enable __initdata;
>  
>  /* early_param wrapper for setup_earlycon() */
>  static int __init param_setup_earlycon(char *buf)
>  {
>  	int err;
>  
> -	/*
> -	 * Just 'earlycon' is a valid param for devicetree earlycons;
> -	 * don't generate a warning from parse_early_params() in that case
> -	 */
> +	/* Just 'earlycon' is a valid param for devicetree and ACPI SPCR. */
>  	if (!buf || !buf[0]) {
>  		if (IS_ENABLED(CONFIG_ACPI_SPCR_TABLE)) {
> -			earlycon_init_is_deferred = true;
> +			earlycon_acpi_spcr_enable = true;
>  			return 0;
>  		} else if (!buf) {
>  			return early_init_dt_scan_chosen_stdout();
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index dc1ebfeeb5ec..9aac8f0ebe23 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1242,9 +1242,12 @@ static inline void acpi_table_upgrade(void) { }
>  
>  #ifdef CONFIG_ACPI_SPCR_TABLE
>  extern bool qdf2400_e44_present;
> -int parse_spcr(bool earlycon);
> +int acpi_parse_spcr(bool enable_earlycon, bool enable_console);
>  #else
> -static inline int parse_spcr(bool earlycon) { return 0; }
> +static inline int acpi_parse_spcr(bool enable_earlycon, bool enable_console)
> +{
> +	return 0;
> +}
>  #endif
>  
>  #if IS_ENABLED(CONFIG_ACPI_GENERIC_GSI)
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 37b044e78333..aefd0e5115da 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -376,10 +376,10 @@ extern int of_setup_earlycon(const struct earlycon_id *match,
>  			     const char *options);
>  
>  #ifdef CONFIG_SERIAL_EARLYCON
> -extern bool earlycon_init_is_deferred __initdata;
> +extern bool earlycon_acpi_spcr_enable __initdata;
>  int setup_earlycon(char *buf);
>  #else
> -static const bool earlycon_init_is_deferred;
> +static const bool earlycon_acpi_spcr_enable;
>  static inline int setup_earlycon(char *buf) { return 0; }
>  #endif
>  

This looks okay to me. Tested on a variety of arm64 platforms.

Reviewed-by: Mark Salter <msalter@redhat.com>
Tested-by: Mark Salter <msalter@redhat.com>