On Friday 15 November 2013 06:23 AM, Mark Rutland wrote:

On Thu, Nov 14, 2013 at 04:46:36PM +0000, Sricharan R wrote:

quoted

Hi Mark,

On Thursday 14 November 2013 07:31 PM, Mark Rutland wrote:

quoted

On Thu, Nov 14, 2013 at 12:18:47PM +0000, Sricharan R wrote:

quoted

In some socs the gic can be preceded by a crossbar IP which
routes the peripheral interrupts to the gic inputs. The peripheral
interrupts are associated with a fixed crossbar input line and the
crossbar routes that to one of the free gic input line.

The DT entries for peripherals provides the fixed crossbar input line
as its interrupt number and the mapping code should associate this with
a free gic input line. This patch adds the support inside the gic irqchip
to handle such routable irqs. The routable irqs are registered in a linear
domain. The registered routable domain's callback should be implemented
to get a free irq and to configure the IP to route it.

Cc: Thomas Gleixner <redacted>
Cc: Linus Walleij <redacted>
Cc: Santosh Shilimkar <redacted>
Cc: Russell King <redacted>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Rajendra Nayak <redacted>
Cc: Marc Zyngier <redacted>
Cc: Grant Likely <redacted>
Cc: Rob Herring <redacted>
Signed-off-by: Sricharan R <redacted>
Acked-by: Santosh Shilimkar <redacted>
---
 [V2] Added default routable-irqs functions to avoid
      unnecessary if checks as per Thomas Gleixner comments
      and renamed routable-irq binding as per
      Kumar Gala [off-list ref] comments.

 [V3] Addressed unnecessary warn-on and updated default
      xlate function as per Thomas Gleixner comments

 Documentation/devicetree/bindings/arm/gic.txt |    6 ++
 drivers/irqchip/irq-gic.c                     |   81 ++++++++++++++++++++++---
 include/linux/irqchip/arm-gic.h               |    7 ++-
 3 files changed, 83 insertions(+), 11 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/gic.txt b/Documentation/devicetree/bindings/arm/gic.txt
index 3dfb0c0..5357745 100644
--- a/Documentation/devicetree/bindings/arm/gic.txt
+++ b/Documentation/devicetree/bindings/arm/gic.txt

@@ -49,6 +49,11 @@ Optional
   regions, used when the GIC doesn't have banked registers. The offset is
   cpu-offset * cpu-nr.
 
+- arm,routable-irqs : Total number of gic irq inputs which are not directly
+		  connected from the peripherals, but are routed dynamically
+		  by a crossbar/multiplexer preceding the GIC. The GIC irq
+		  input line is assigned dynamically when the corresponding
+		  peripheral's crossbar line is mapped.

I'm not keen on the design of the arm,routable-irqs property. The set of
IRQs which the crossbar IP can use is a property of which IRQ lines it
has routed to the GIC. I don't see why that should be considered a
property of the GIC; it's a property of the crossbar IP's attachment to
the GIC.

Given we already have a mechanism for describing the attachment (i.e.
the interrupts property) where the property appears on the node for the
device generating/propagating the interrupt, I don't see why we should
do differently here.

 We did try using interrupts=<> property for all peripherals and
 mapping them as crossbar's parent. But that approach of representing
 crossbar as a interrupt parent was not accepted, since the crossbar
 was just routing the interrupts from peripherals to GIC and nothing more.
 Also  mapping all the interrupts using interrupt-map like property by a fixed way
 in DTS itself was considered hacky

I'm not suggesting you should interrupt-map. I agree that that
interrupt-map is not suitable for a dynamically configurable device like
the crossbar.

When you say that the crossbar is just routing the interrupts, at what
level is it doing so? Does it accept a logical interrupt and output
another logical interrupt, or does it just connect the two lines
electrically?

Its just makes electrical connection between input and output line and
thats it.

Regards,
Santosh