Date:	Mon, 9 Feb 2015 07:07:54 +0000
From:	Will Deacon <will.deacon@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Mark Rutland <Mark.Rutland@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	"jcm@...hat.com" <jcm@...hat.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>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"phoenix.liyi@...wei.com" <phoenix.liyi@...wei.com>,
	Timur Tabi <timur@...eaurora.org>,
	Ashwin Chaugule <ashwinc@...eaurora.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	Mark Langsdorf <mlangsdo@...hat.com>,
	"wangyijing@...wei.com" <wangyijing@...wei.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 v8 15/21] ARM64 / ACPI: Introduce ACPI_IRQ_MODEL_GIC and
 register device's gsi

On Mon, Feb 09, 2015 at 06:53:31AM +0000, Hanjun Guo wrote:
> On 2015年02月09日 14:34, Will Deacon wrote:
> > On Mon, Feb 02, 2015 at 12:45:43PM +0000, Hanjun Guo wrote:
> >> Introduce ACPI_IRQ_MODEL_GIC which is needed for ARM64 as GIC is
> >> used, and then register device's gsi with the core IRQ subsystem.
> >>
> >> acpi_register_gsi() is similar to DT based irq_of_parse_and_map(),
> >> since gsi is unique in the system, so use hwirq number directly
> >> for the mapping.
> >>
> >> We are going to implement stacked domains when GICv2m, GICv3, ITS
> >> support are added.
> >>
> >> CC: Marc Zyngier <marc.zyngier@....com>
> >> Originally-by: Amit Daniel Kachhap <amit.daniel@...sung.com>
> >> Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> >> Tested-by: Yijing Wang <wangyijing@...wei.com>
> >> Tested-by: Mark Langsdorf <mlangsdo@...hat.com>
> >> Tested-by: Jon Masters <jcm@...hat.com>
> >> Tested-by: Timur Tabi <timur@...eaurora.org>
> >> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> >> ---
> >>   arch/arm64/kernel/acpi.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>   drivers/acpi/bus.c       |  3 ++
> >>   include/linux/acpi.h     |  1 +
> >>   3 files changed, 77 insertions(+)
> >>
> >> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> >> index f80caef..f86a982 100644
> >> --- a/arch/arm64/kernel/acpi.c
> >> +++ b/arch/arm64/kernel/acpi.c
> >> @@ -38,6 +38,12 @@ EXPORT_SYMBOL(acpi_pci_disabled);
> >>   static int enabled_cpus;	/* Processors (GICC) with enabled flag in MADT */
> >>
> >>   /*
> >> + * Since we're on ARM, the default interrupt routing model
> >> + * clearly has to be GIC.
> >> + */
> >> +enum acpi_irq_model_id acpi_irq_model = ACPI_IRQ_MODEL_GIC;
> >> +
> >> +/*
> >>    * __acpi_map_table() will be called before page_init(), so early_ioremap()
> >>    * or early_memremap() should be called here to for ACPI table mapping.
> >>    */
> >> @@ -185,6 +191,73 @@ void __init acpi_init_cpus(void)
> >>   	pr_info("%d CPUs enabled, %d CPUs total\n", enabled_cpus, total_cpus);
> >>   }
> >>
> >> +int acpi_gsi_to_irq(u32 gsi, unsigned int *irq)
> >> +{
> >> +	*irq = irq_find_mapping(NULL, gsi);
> >> +
> >> +	return 0;
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
> >> +
> >> +/*
> >> + * success: return IRQ number (>0)
> >> + * failure: return =< 0
> >> + */
> >> +int acpi_register_gsi(struct device *dev, u32 gsi, int trigger, int polarity)
> >> +{
> >> +	unsigned int irq;
> >> +	unsigned int irq_type;
> >> +
> >> +	/*
> >> +	 * ACPI have no bindings to indicate SPI or PPI, so we
> >> +	 * use different mappings from DT in ACPI.
> >> +	 *
> >> +	 * For FDT
> >> +	 * PPI interrupt: in the range [0, 15];
> >> +	 * SPI interrupt: in the range [0, 987];
> >> +	 *
> >> +	 * For ACPI, GSI should be unique so using
> >> +	 * the hwirq directly for the mapping:
> >> +	 * PPI interrupt: in the range [16, 31];
> >> +	 * SPI interrupt: in the range [32, 1019];
> >> +	 */
> >> +
> >> +	if (trigger == ACPI_EDGE_SENSITIVE &&
> >> +				polarity == ACPI_ACTIVE_LOW)
> >> +		irq_type = IRQ_TYPE_EDGE_FALLING;
> >> +	else if (trigger == ACPI_EDGE_SENSITIVE &&
> >> +				polarity == ACPI_ACTIVE_HIGH)
> >> +		irq_type = IRQ_TYPE_EDGE_RISING;
> >> +	else if (trigger == ACPI_LEVEL_SENSITIVE &&
> >> +				polarity == ACPI_ACTIVE_LOW)
> >> +		irq_type = IRQ_TYPE_LEVEL_LOW;
> >> +	else if (trigger == ACPI_LEVEL_SENSITIVE &&
> >> +				polarity == ACPI_ACTIVE_HIGH)
> >> +		irq_type = IRQ_TYPE_LEVEL_HIGH;
> >> +	else
> >> +		irq_type = IRQ_TYPE_NONE;
> >> +
> >> +	/*
> >> +	 * Since only one GIC is supported in ACPI 5.0, we can
> >> +	 * create mapping refer to the default domain
> >> +	 */
> >> +	irq = irq_create_mapping(NULL, gsi);
> >> +	if (!irq)
> >> +		return irq;
> >> +
> >> +	/* Set irq type if specified and different than the current one */
> >> +	if (irq_type != IRQ_TYPE_NONE &&
> >> +		irq_type != irq_get_trigger_type(irq))
> >> +		irq_set_irq_type(irq, irq_type);
> >> +	return irq;
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_register_gsi);
> >> +
> >> +void acpi_unregister_gsi(u32 gsi)
> >> +{
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_unregister_gsi);
> >> +
> >>   static int __init acpi_parse_fadt(struct acpi_table_header *table)
> >>   {
> >>   	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
> >
> > Does this code *have* to sit under arch/arm64? I can't see anything
> > architecture-specific about it and the bulk of the functions map directly
> > onto irq domain callbacks. I know that the answer is probably "we can fix
> > that in the future", but it doesn't seem like a huge amount of effort to
> > get the right abstractions in place from the beginning so that we don't
> > have to churn this stuff later on.
> 
> Do you mean move acpi_register_gsi()/acpi_unregister_gsi() to irqdomain
> related file?
> 
> Since x86 and IA64 have their arch specific acpi_register_gsi()
> /acpi_unregister_gsi(), we will got compile errors on x86 and IA64
> platforms.

Right, but nobody builds a single kernel image supporting x86 and arm, so
this doesn't sound impossible to fix.

The code here basically consists of:

  - Definition of acpi_irq_model. That can stay here for now.
  - Empty stub for acpi_unregister_gsi -- should be in core code
  - acpi_gsi_to_irq -- maps directly to irq_find_mapping, core code.
  - Code to translate an ACPI interrupt type to a Linux IRQ subsystem type
  - Instantiaton of an irq mapping

None of that has anything to do with the arm64 architecture. If we have to
make some small changes to core code to accommodate a non-x86 architecture,
then I think we should at least consider that first.

Will
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