linux-kernel - Re: [PATCH 06/19] ARM64 / ACPI: Parse FADT table to get PSCI flags for PSCI init

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Message-ID: <53D7CE6F.1050407@arm.com>
Date:	Tue, 29 Jul 2014 17:40:15 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>
CC:	Sudeep Holla <sudeep.holla@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mark Brown <broonie@...aro.org>,
	Robert Richter <rric@...nel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/19] ARM64 / ACPI: Parse FADT table to get PSCI flags
 for PSCI init



On 24/07/14 14:00, Hanjun Guo wrote:
> There are two flags: PSCI_COMPLIANT and PSCI_USE_HVC. When set,
> the former signals to the OS that the hardware is PSCI compliant.
> The latter selects the appropriate conduit for PSCI calls by
> toggling between Hypervisor Calls (HVC) and Secure Monitor Calls
> (SMC).
>
> FADT table contains such information, parse FADT to get the flags
> for PSCI init. Since ACPI 5.1 doesn't support self defined PSCI
> function IDs, which means that only PSCI 0.2+ is supported in ACPI.
>
> At the same time, only ACPI 5.1 or higher verison supports PSCI,
> and FADT Major.Minor version was introduced in ACPI 5.1, so we
> will check the version and only parse FADT table with version >= 5.1.
>
> If firmware provides ACPI tables with ACPI version less than 5.1,
> OS will be messed up with those information and have no way to
> bring up secondery CPUs, so disable ACPI if we get an FADT table
> with version less that 5.1.
>
> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> Signed-off-by: Graeme Gregory <graeme.gregory@...aro.org>
> ---
>   arch/arm64/include/asm/acpi.h |    2 +
>   arch/arm64/kernel/acpi.c      |   50 ++++++++++++++++++++++
>   arch/arm64/kernel/psci.c      |   95 +++++++++++++++++++++++++++++------------
>   arch/arm64/kernel/setup.c     |    2 +
>   4 files changed, 121 insertions(+), 28 deletions(-)
>
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index 44b617f..67dac90 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -18,6 +18,8 @@ extern int acpi_disabled;
>   extern int acpi_noirq;
>   extern int acpi_pci_disabled;
>   extern int acpi_strict;
> +extern int acpi_psci_present;
> +extern int acpi_psci_use_hvc;
>
>   static inline void disable_acpi(void)
>   {
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index f5a10b5..374926f 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -11,6 +11,8 @@
>    *  published by the Free Software Foundation.
>    */
>
> +#define pr_fmt(fmt) "ACPI: " fmt
> +
>   #include <linux/init.h>
>   #include <linux/acpi.h>
>   #include <linux/cpumask.h>
> @@ -34,6 +36,12 @@ EXPORT_SYMBOL(acpi_disabled);
>   int acpi_pci_disabled;		/* skip ACPI PCI scan and IRQ initialization */
>   EXPORT_SYMBOL(acpi_pci_disabled);
>
> +/* 1 to indicate PSCI is implemented */
> +int acpi_psci_present;
> +
> +/* 1 to indicate HVC must be used instead of SMC as the PSCI conduit */
> +int acpi_psci_use_hvc;
> +

These can be boolean but can be removed IMO, see below.

>   /*
>    * __acpi_map_table() will be called before page_init(), so early_ioremap()
>    * or early_memremap() should be called here to for ACPI table mapping.
> @@ -54,6 +62,33 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
>   	early_iounmap(map, size);
>   }
>
> +static int __init acpi_parse_fadt(struct acpi_table_header *table)
> +{
> +	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
> +
> +	/*
> +	 * Revision in table header is the FADT Major version,
> +	 * and there is a minor version of FADT which was introduced
> +	 * by ACPI 5.1, we only deal with ACPI 5.1 or higher version
> +	 * to get arm boot flags, or we will disable ACPI.
> +	 */
> +	if (table->revision < 5 || fadt->minor_version < 1) {
> +		pr_info("FADT version is %d.%d, no PSCI support, should be 5.1 or higher\n",
> +			table->revision, fadt->minor_version);
> +		acpi_psci_present = 0;
> +		disable_acpi();
> +		return -EINVAL;
> +	}
> +
> +	if (acpi_gbl_FADT.arm_boot_flags & ACPI_FADT_PSCI_COMPLIANT)
> +		acpi_psci_present = 1;
> +
> +	if (acpi_gbl_FADT.arm_boot_flags & ACPI_FADT_PSCI_USE_HVC)
> +		acpi_psci_use_hvc = 1;
> +

Why not make this macros instead of global variables as I suggested in
previous version. acpi_gbl_FADT is already global and you can avoid
creating new one especially they are just used on boot/init.

Regards,
Sudeep

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