Re: [PATCH v2 1/2] acpi, spcr: Make SPCR avialable to other architectures

[Lorenzo Pieralisi]

[+Mark, Graeme]

In $SUBJECT, s/avialable/available

On Mon, Dec 11, 2017 at 10:50:58AM -0500, Prarit Bhargava wrote:
> Other architectures can use SPCR to setup an early console or console
> but the current code is ARM64 specific.

I see nothing ARM64 specific in current code (apart from some
ACPICA macros with an ARM tag in them) please explain to me
what's preventing you to reuse current code on x86.

> Change the name of parse_spcr() to acpi_parse_spcr().  Add a weak
> function acpi_arch_setup_console() that can be used for arch-specific
> setup.  Move flags into ACPI code.  Update the Documention on the use of
> the SPCR.
> 
> [v2]: Don't return an error in the baud_rate check of acpi_parse_spcr().
> Keep ACPI_SPCR_TABLE selected for ARM64.  Fix 8-bit port access width
> mmio value.  Move baud rate check earlier.

This does not belong in the commit log.

> Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
> Cc: linux-doc@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Cc: linux-acpi@xxxxxxxxxxxxxxx
> Cc: linux-serial@xxxxxxxxxxxxxxx
> Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
> Cc: Lv Zheng <lv.zheng@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Timur Tabi <timur@xxxxxxxxxxxxxx>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |   6 +-
>  arch/arm64/kernel/acpi.c                        | 128 ++++++++++++++++-
>  drivers/acpi/Kconfig                            |   7 +-
>  drivers/acpi/spcr.c                             | 175 ++++++------------------
>  drivers/tty/serial/earlycon.c                   |  15 +-
>  include/linux/acpi.h                            |  11 +-
>  include/linux/serial_core.h                     |   2 -
>  7 files changed, 184 insertions(+), 160 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 6571fbfdb2a1..0d173289c67e 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -914,9 +914,9 @@
>  
>  	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.
>  
>  		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..b3e33bbdf3b7 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -25,7 +25,6 @@
>  #include <linux/memblock.h>
>  #include <linux/of_fdt.h>
>  #include <linux/smp.h>
> -#include <linux/serial_core.h>
>  
>  #include <asm/cputype.h>
>  #include <asm/cpu_ops.h>
> @@ -177,6 +176,128 @@ static int __init acpi_fadt_sanity_check(void)
>  	return ret;
>  }
>  
> +/*
> + * Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
> + * 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
> + * acpi_parse_spcr().
> + */
> +bool qdf2400_e44_present;
> +EXPORT_SYMBOL(qdf2400_e44_present);

My eyes, this is horrible but it is not introduced by this patch. It
would have been much better if:

drivers/tty/serial/amba-pl011.c

parsed the SPCR table (again) to detect it instead of relying on this
horrible exported flag.

> +
> +/*
> + * Some Qualcomm Datacenter Technologies SoCs have a defective UART BUSY bit.
> + * Detect them by examining the OEM fields in the SPCR header, similar to PCI
> + * quirk detection in pci_mcfg.c.
> + */
> +static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
> +{
> +	if (memcmp(h->oem_id, "QCOM  ", ACPI_OEM_ID_SIZE))
> +		return false;
> +
> +	if (!memcmp(h->oem_table_id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
> +		return true;
> +
> +	if (!memcmp(h->oem_table_id, "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
> +			h->oem_revision == 1)
> +		return true;
> +
> +	return false;
> +}
> +
> +/*
> + * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
> + * register aligned to 32-bit. In addition, the BIOS also encoded the
> + * access width to be 8 bits. This function detects this errata condition.
> + */
> +static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
> +{
> +	bool xgene_8250 = false;
> +
> +	if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
> +		return false;
> +
> +	if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE) &&
> +	    memcmp(tb->header.oem_id, "HPE   ", ACPI_OEM_ID_SIZE))
> +		return false;
> +
> +	if (!memcmp(tb->header.oem_table_id, "XGENESPC",
> +	    ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
> +		xgene_8250 = true;
> +
> +	if (!memcmp(tb->header.oem_table_id, "ProLiant",
> +	    ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 1)
> +		xgene_8250 = true;
> +
> +	return xgene_8250;
> +}
> +
> +int acpi_arch_setup_console(struct acpi_table_spcr *table,
> +			    char *opts, char *uart, char *iotype,
> +			    int baud_rate, bool earlycon)
> +{
> +	if (table->header.revision < 2) {
> +		pr_err("wrong table version\n");
> +		return -ENOENT;
> +	}
> +
> +	switch (table->interface_type) {
> +	case ACPI_DBG2_ARM_SBSA_32BIT:
> +		snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio32");
> +		/* fall through */
> +	case ACPI_DBG2_ARM_PL011:
> +	case ACPI_DBG2_ARM_SBSA_GENERIC:
> +	case ACPI_DBG2_BCM2835:
> +		snprintf(uart, ACPI_SPCR_BUF_SIZE, "pl011");
> +		break;
> +	default:
> +		if (strlen(uart) == 0)
> +			return -ENOENT;
> +	}
> +
> +	/*
> +	 * If the E44 erratum is required, then we need to tell the pl011
> +	 * driver to implement the work-around.
> +	 *
> +	 * The global variable is used by the probe function when it
> +	 * creates the UARTs, whether or not they're used as a console.
> +	 *
> +	 * If the user specifies "traditional" earlycon, the qdf2400_e44
> +	 * console name matches the EARLYCON_DECLARE() statement, and
> +	 * SPCR is not used.  Parameter "earlycon" is false.
> +	 *
> +	 * If the user specifies "SPCR" earlycon, then we need to update
> +	 * the console name so that it also says "qdf2400_e44".  Parameter
> +	 * "earlycon" is true.
> +	 *
> +	 * For consistency, if we change the console name, then we do it
> +	 * for everyone, not just earlycon.
> +	 */
> +	if (qdf2400_erratum_44_present(&table->header)) {
> +		qdf2400_e44_present = true;
> +		if (earlycon)
> +			snprintf(uart, ACPI_SPCR_BUF_SIZE, "qdf2400_e44");
> +	}
> +
> +	if (xgene_8250_erratum_present(table)) {
> +		snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio32");
> +
> +		/* for xgene v1 and v2 we don't know the clock rate of the
> +		 * UART so don't attempt to change to the baud rate state
> +		 * in the table because driver cannot calculate the dividers
> +		 */
> +		snprintf(opts, ACPI_SPCR_OPTS_SIZE, "%s,%s,0x%llx", uart,
> +			 iotype, table->serial_port.address);
> +	} else {
> +		snprintf(opts, ACPI_SPCR_OPTS_SIZE, "%s,%s,0x%llx,%d", uart,
> +			 iotype, table->serial_port.address, baud_rate);
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(acpi_arch_setup_console);

EXPORT_SYMBOL() ? Why ?

BTW, why do we need an arch hook ? I do not see anything that prevents
you from using this code on x86 systems - is there anything arch
specific in the SPCR specification itself ?

> +
>  /*
>   * acpi_boot_table_init() called from setup_arch(), always.
>   *	1. find RSDP and get its address, and then find XSDT
> @@ -230,10 +351,11 @@ void __init acpi_boot_table_init(void)
>  
>  done:
>  	if (acpi_disabled) {
> -		if (earlycon_init_is_deferred)
> +		if (console_acpi_spcr_enable)
>  			early_init_dt_scan_chosen_stdout();
>  	} else {
> -		parse_spcr(earlycon_init_is_deferred);
> +		/* Always enable the ACPI SPCR console */
> +		acpi_parse_spcr(console_acpi_spcr_enable);
>  		if (IS_ENABLED(CONFIG_ACPI_BGRT))
>  			acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);
>  	}
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index 46505396869e..9ae98eeada76 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 ARM64

You need to remove the selection in arch/arm64 then. Also, moving away
from a non-visible config may have consequences on ARM64, Graeme and
Mark are more familiar with the SPCR dependencies so please chime in.

> +	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..f4bb8110e404 100644
> --- a/drivers/acpi/spcr.c
> +++ b/drivers/acpi/spcr.c
> @@ -16,65 +16,18 @@
>  #include <linux/kernel.h>
>  #include <linux/serial_core.h>
>  
> -/*
> - * Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
> - * 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().
> - */
> -bool qdf2400_e44_present;
> -EXPORT_SYMBOL(qdf2400_e44_present);
> -
> -/*
> - * Some Qualcomm Datacenter Technologies SoCs have a defective UART BUSY bit.
> - * Detect them by examining the OEM fields in the SPCR header, similiar to PCI
> - * quirk detection in pci_mcfg.c.
> - */
> -static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
> -{
> -	if (memcmp(h->oem_id, "QCOM  ", ACPI_OEM_ID_SIZE))
> -		return false;
> -
> -	if (!memcmp(h->oem_table_id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
> -		return true;
> -
> -	if (!memcmp(h->oem_table_id, "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
> -			h->oem_revision == 1)
> -		return true;
> -
> -	return false;
> -}
> -
> -/*
> - * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
> - * register aligned to 32-bit. In addition, the BIOS also encoded the
> - * access width to be 8 bits. This function detects this errata condition.
> - */
> -static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
> +int __weak acpi_arch_setup_console(struct acpi_table_spcr *table,
> +				   char *opts, char *uart, char *iotype,
> +				   int baud_rate, bool earlycon)
>  {
> -	bool xgene_8250 = false;
> -
> -	if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
> -		return false;
> -
> -	if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE) &&
> -	    memcmp(tb->header.oem_id, "HPE   ", ACPI_OEM_ID_SIZE))
> -		return false;
> -
> -	if (!memcmp(tb->header.oem_table_id, "XGENESPC",
> -	    ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
> -		xgene_8250 = true;
> -
> -	if (!memcmp(tb->header.oem_table_id, "ProLiant",
> -	    ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 1)
> -		xgene_8250 = true;
> -
> -	return xgene_8250;
> +	snprintf(opts, ACPI_SPCR_OPTS_SIZE, "%s,%s,0x%llx,%d", uart, iotype,
> +		 table->serial_port.address, baud_rate);
> +	return 0;
>  }
>  
> +bool console_acpi_spcr_enable __initdata;
>  /**
> - * 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
>   *
> @@ -86,13 +39,13 @@ static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
>   * 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 earlycon)
>  {
> -	static char opts[64];
> +	static char opts[ACPI_SPCR_OPTS_SIZE];
> +	static char uart[ACPI_SPCR_BUF_SIZE];
> +	static char iotype[ACPI_SPCR_BUF_SIZE];
>  	struct acpi_table_spcr *table;
>  	acpi_status status;
> -	char *uart;
> -	char *iotype;
>  	int baud_rate;
>  	int err;
>  
> @@ -105,48 +58,6 @@ 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->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> -		switch (ACPI_ACCESS_BIT_WIDTH((
> -			table->serial_port.access_width))) {
> -		default:
> -			pr_err("Unexpected SPCR Access Width.  Defaulting to byte size\n");
> -		case 8:
> -			iotype = "mmio";
> -			break;
> -		case 16:
> -			iotype = "mmio16";
> -			break;
> -		case 32:
> -			iotype = "mmio32";
> -			break;
> -		}
> -	} else
> -		iotype = "io";
> -
> -	switch (table->interface_type) {
> -	case ACPI_DBG2_ARM_SBSA_32BIT:
> -		iotype = "mmio32";
> -		/* fall through */
> -	case ACPI_DBG2_ARM_PL011:
> -	case ACPI_DBG2_ARM_SBSA_GENERIC:
> -	case ACPI_DBG2_BCM2835:
> -		uart = "pl011";
> -		break;
> -	case ACPI_DBG2_16550_COMPATIBLE:
> -	case ACPI_DBG2_16550_SUBSET:
> -		uart = "uart";
> -		break;
> -	default:
> -		err = -ENOENT;
> -		goto done;
> -	}
> -
>  	switch (table->baud_rate) {
>  	case 3:
>  		baud_rate = 9600;
> @@ -165,43 +76,36 @@ int __init parse_spcr(bool earlycon)
>  		goto done;
>  	}
>  
> -	/*
> -	 * If the E44 erratum is required, then we need to tell the pl011
> -	 * driver to implement the work-around.
> -	 *
> -	 * The global variable is used by the probe function when it
> -	 * creates the UARTs, whether or not they're used as a console.
> -	 *
> -	 * If the user specifies "traditional" earlycon, the qdf2400_e44
> -	 * console name matches the EARLYCON_DECLARE() statement, and
> -	 * SPCR is not used.  Parameter "earlycon" is false.
> -	 *
> -	 * If the user specifies "SPCR" earlycon, then we need to update
> -	 * the console name so that it also says "qdf2400_e44".  Parameter
> -	 * "earlycon" is true.
> -	 *
> -	 * For consistency, if we change the console name, then we do it
> -	 * for everyone, not just earlycon.
> -	 */
> -	if (qdf2400_erratum_44_present(&table->header)) {
> -		qdf2400_e44_present = true;
> -		if (earlycon)
> -			uart = "qdf2400_e44";
> +	switch (table->interface_type) {
> +	case ACPI_DBG2_16550_COMPATIBLE:
> +	case ACPI_DBG2_16550_SUBSET:
> +		snprintf(uart, ACPI_SPCR_BUF_SIZE, "uart");
> +		break;
> +	default:
> +		break;
>  	}
>  
> -	if (xgene_8250_erratum_present(table)) {
> -		iotype = "mmio32";
> +	if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> +		u8 width = ACPI_ACCESS_BIT_WIDTH((
> +					table->serial_port.access_width));
> +		switch (width) {
> +		default:
> +			pr_err("Unexpected SPCR Access Width.  Defaulting to byte size\n");
> +		case 8:
> +			snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio");
> +			break;
> +		case 16:
> +		case 32:
> +			snprintf(iotype, ACPI_SPCR_BUF_SIZE, "mmio%d", width);
> +			break;
> +		}
> +	} else
> +		snprintf(iotype, ACPI_SPCR_BUF_SIZE, "io");
>  
> -		/* for xgene v1 and v2 we don't know the clock rate of the
> -		 * UART so don't attempt to change to the baud rate state
> -		 * in the table because driver cannot calculate the dividers
> -		 */
> -		snprintf(opts, sizeof(opts), "%s,%s,0x%llx", uart, iotype,
> -			 table->serial_port.address);
> -	} else {
> -		snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
> -			 table->serial_port.address, baud_rate);
> -	}
> +	err = acpi_arch_setup_console(table, opts, uart, iotype, baud_rate,
> +				      earlycon);
> +	if (err)
> +		goto done;
>  
>  	pr_info("console: %s\n", opts);
>  
> @@ -209,7 +113,6 @@ int __init parse_spcr(bool earlycon)
>  		setup_earlycon(opts);
>  
>  	err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);
> -

Unintended change.

>  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..b22afb62c7a3 100644
> --- a/drivers/tty/serial/earlycon.c
> +++ b/drivers/tty/serial/earlycon.c
> @@ -196,26 +196,15 @@ int __init setup_earlycon(char *buf)
>  	return -ENOENT;
>  }
>  
> -/*
> - * 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()
> - */
> -bool earlycon_init_is_deferred __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;
> +			console_acpi_spcr_enable = true;

I am not familiar with this code, I would ask Graeme and Mark to check
if this change is correct, the logic seems correct to me but I may be
missing some corner cases.

>  			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..875d7327d91c 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1241,10 +1241,17 @@ static inline bool acpi_has_watchdog(void) { return false; }
>  #endif
>  
>  #ifdef CONFIG_ACPI_SPCR_TABLE
> +#define ACPI_SPCR_OPTS_SIZE 64
> +#define ACPI_SPCR_BUF_SIZE 32
>  extern bool qdf2400_e44_present;
> -int parse_spcr(bool earlycon);
> +extern bool console_acpi_spcr_enable __initdata;
> +extern int acpi_arch_setup_console(struct acpi_table_spcr *table,
> +				   char *opts, char *uart, char *iotype,
> +				   int baud_rate, bool earlycon);
> +int acpi_parse_spcr(bool earlycon);
>  #else
> -static inline int parse_spcr(bool earlycon) { return 0; }
> +static const bool console_acpi_spcr_enable;

The assignment in param_setup_earlycon won't compile.

Lorenzo