linux-kernel - Re: [PATCH v2 05/18] ARM64 / ACPI: Parse FADT table to get PSCI flags for PSCI init

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Message-ID: <53F2C983.8000800@linaro.org>
Date:	Tue, 19 Aug 2014 11:50:27 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	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@...nel.org>, Rob Herring <robh@...nel.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>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [PATCH v2 05/18] ARM64 / ACPI: Parse FADT table to get PSCI flags
 for PSCI init

On 2014-8-18 22:27, Catalin Marinas wrote:
> On Mon, Aug 04, 2014 at 04:28:12PM +0100, 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.
> 
> Actually it signals that the firmware is PSCI compliant. The hardware
> doesn't care much.

Right, I will update it.

> 
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> index 6400312..6e04868 100644
>> --- a/arch/arm64/include/asm/acpi.h
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -19,6 +19,18 @@ extern int acpi_disabled;
>>  extern int acpi_noirq;
>>  extern int acpi_pci_disabled;
>>  
>> +/* 1 to indicate PSCI 0.2+ is implemented */
>> +static inline bool acpi_psci_present(void)
>> +{
>> +	return !!(acpi_gbl_FADT.arm_boot_flags & ACPI_FADT_PSCI_COMPLIANT);
>> +}
>> +
>> +/* 1 to indicate HVC must be used instead of SMC as the PSCI conduit */
>> +static inline bool acpi_psci_use_hvc(void)
>> +{
>> +	return !!(acpi_gbl_FADT.arm_boot_flags & ACPI_FADT_PSCI_USE_HVC);
>> +}
> 
> Do we actually need !! here? Shouldn't the compiler figure out
> conversion to bool automatically?

I thought !! will explicitly show that it's a bool value and
improve the readability of the code, but I'm ok to remove !!
here.

> 
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> index 9cf9127..69a315d 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>
>> @@ -47,6 +49,26 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
>>  	early_memunmap(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_revision < 1) {
> 
> If we ever get revision 6.0, this would trigger.

Yes, good catch, actually I already fixed that in my local git repo,

+       if (table->revision > 5 ||
+           (table->revision == 5 && fadt->minor_revision >= 1)) {
+               return 0;
+       } else {
+               pr_info("FADT revision is %d.%d, no PSCI support, should be 5.1
or higher\n",
+                       table->revision, fadt->minor_revision);
+               disable_acpi();
+               return -EINVAL;
+       }

> 
>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
>> index 85c6326..dfc4e4f3 100644
>> --- a/arch/arm64/kernel/setup.c
>> +++ b/arch/arm64/kernel/setup.c
>> @@ -395,6 +395,8 @@ void __init setup_arch(char **cmdline_p)
>>  	efi_idmap_init();
>>  
>>  	cpu_logical_map(0) = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
>> +	acpi_boot_init();
>> +
>>  	unflatten_device_tree();
> 
> Unless that's changed in a subsequent patch, do we still need to call
> unflatten_device_tree() if ACPI was successful?

No, we don't. in [PATCH v2 16/18], we will not call unflatten_device_tree()
if ACPI is successful. Since the CONFIG_ACPI is not enabled for ARM64 (will
enable it in the last patch), so acpi_boot_init() is a stub empty function
here.

> 
>>  	psci_init();
> 
> I would also rename this to something like psci_dt_init() and move the
> acpi_disabled check here rather than in the callee.

thanks for the suggestion, I will update my patch :)

Thanks
Hanjun


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