Subject: [PATCH 3/5] irqchip: crossbar: Skip some irqs from getting mapped to crossbar

From: [email-masked] (Nishanth Menon)
Date: Fri, 9 May 2014 07:54:55 -0500

On 05/08/2014 11:22 PM, Joel Fernandes wrote:
> On Thu, May 8, 2014 at 7:25 PM, Santosh Shilimkar
> <[email-masked]> wrote:
[...]
> Ok, thanks for pointing to the post.
> 

Yep - thanks Santosh for clarifying this. Now, we still have the
issues that I pointed out in [1] - without resolving which, we should
not enable crossbar for dra74x/72x.

A. taking example of PMU
	interrupts = <GIC_SPI 131 IRQ_TYPE_LEVEL_HIGH>
this wont work. instead the crossbar driver needs some sort of a hint
to know that it should not map these on crossbar register instead
assign GIC mapping directly.

I propose doing the following
#define GIC_CROSSBAR_PASSTHROUGH(irq_no) ((irq_no) | (0x1 << 31))

and dts will define the following:
interrupts = <GIC_SPI GIC_CROSSBAR_PASSTHROUGH(131) IRQ_TYPE_LEVEL_HIGH>

This will also work for the other cases (B.2, B.3)

For B.2: L3_APP_IRQ:
instead of:
interrupts = <GIC_SPI  5 IRQ_TYPE_LEVEL_HIGH>
we do:
interrupts = <GIC_SPI GIC_CROSSBAR_PASSTHROUGH(10) IRQ_TYPE_LEVEL_HIGH>

For B.3: NMI
interrupts = <GIC_SPI GIC_CROSSBAR_PASSTHROUGH(133) IRQ_TYPE_LEVEL_HIGH>

xlate is easy ->

diff --git a/drivers/irqchip/irq-crossbar.c
b/drivers/irqchip/irq-crossbar.c
index de021638..fd09ab4 100644
--- a/drivers/irqchip/irq-crossbar.c
+++ b/drivers/irqchip/irq-crossbar.c
@@ -112,6 +112,10 @@ static int crossbar_domain_xlate(struct
irq_domain *d,
 {
        unsigned long ret;

+       /* Check to see if direct GIC mapping is required */
+       if (intspec[1] & BIT(31))
+               return intspec[1] & ~BIT[31];
+
        ret = get_prev_map_irq(intspec[1]);
        if (!IS_ERR_VALUE(ret))
                goto found;

But then, crossbar_domain_map and crossbar_domain_unmap need hints as
well to know that there is no corresponding crossbar registers.
Have'nt thought through that yet. Looking to hear about opinions here.

[1] http://marc.info/?l=linux-arm-kernel&m=139958155312421&w=2
-- 
Regards,
Nishanth Menon