[PATCH 1/5] ARM: gic: Add hooks for architecture specific extensions

On Tue, Jan 25, 2011 at 11:22 PM, Santosh Shilimkar
[off-list ref] wrote:

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-----Original Message-----
From: ccross at google.com [mailto:ccross at google.com] On Behalf Of
Colin Cross
Sent: Wednesday, January 26, 2011 2:25 AM
To: Santosh Shilimkar
Cc: linux-arm-kernel at lists.infradead.org; linux-
omap at vger.kernel.org; catalin.marinas at arm.com;
linux at arm.linux.org.uk; linus.ml.walleij at gmail.com; Russell King
Subject: Re: [PATCH 1/5] ARM: gic: Add hooks for architecture
specific extensions

On Mon, Jan 24, 2011 at 7:03 PM, Colin Cross [off-list ref]
wrote:

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On Mon, Jan 24, 2011 at 12:51 AM, Santosh Shilimkar
[off-list ref] wrote:

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Few architectures combine the GIC with an external interrupt

controller.

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On such systems it may be necessary to update both the GIC

registers

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and the external controller's registers to control IRQ behavior.

This can be addressed in couple of possible methods.
?1. ? ? Export common GIC routines along with 'struct irq_chip

gic_chip'

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? ? ? ?and allow architectures to have custom function by

override.

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?2. ? ? Provide architecture specific function pointer hooks
? ? ? ?within GIC library and leave platforms to add the

necessary

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? ? ? ?code as part of these hooks.

First one might be non-intrusive but have few shortcomings like

arch needs

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to have there own custom gic library. Locks used should be common

since it

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caters to same IRQs etc. Maintenance point of view also it leads

to

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multiple file fixes.

The second probably is cleaner and portable. It ensures that all

the

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common GIC infrastructure is not touched and also provides archs

to

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address their specific issue.

This method would work for most of Tegra's needs, although we

would

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need gic_set_type and gic_ack_irq to have arch extensions as well.
However, it does not allow for irq_retrigger, which can be

implemented

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on Tegra.

irq_retrigger does work with this method, the core IRQ code checks
for
a return value if the retrigger was successful. ?Tegra works with
your
patch along with these changes:

Great.
Can I fold below changes in my patch and add you ack and tested-by?

Sure

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diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
index 0b6c043..7993f07 100644
--- a/arch/arm/common/gic.c
+++ b/arch/arm/common/gic.c

@@ -90,6 +90,8 @@ static inline unsigned int gic_irq(struct irq_data

*d)
?static void gic_ack_irq(struct irq_data *d)
?{
? ? ? spin_lock(&irq_controller_lock);
+ ? ? if (gic_arch_extn.irq_ack)
+ ? ? ? ? ? ? gic_arch_extn.irq_ack(d);
? ? ? writel(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
? ? ? spin_unlock(&irq_controller_lock);
?}

@@ -161,6 +163,14 @@ static int gic_set_type(struct irq_data *d,

unsigned int type)
? ? ? return 0;
?}

+static int gic_retrigger(struct irq_data *d)
+{
+ ? ? if (gic_arch_extn.irq_retrigger)
+ ? ? ? ? ? ? return gic_arch_extn.irq_retrigger(d);
+
+ ? ? return 0;
+}
+
?#ifdef CONFIG_SMP
?static int
?gic_set_cpu(struct irq_data *d, const struct cpumask *mask_val,
bool force)

@@ -234,6 +244,7 @@ static struct irq_chip gic_chip = {

? ? ? .irq_mask ? ? ? ? ? ? ? = gic_mask_irq,
? ? ? .irq_unmask ? ? ? ? ? ? = gic_unmask_irq,
? ? ? .irq_set_type ? ? ? ? ? = gic_set_type,
+ ? ? .irq_retrigger ? ? ? ? ?= gic_retrigger,
?#ifdef CONFIG_SMP
? ? ? .irq_set_affinity ? ? ? = gic_set_cpu,
?#endif