linux-kernel - Re: [PATCH v3 22/25] irq_domain/x86: Convert x86 (embedded) to use common irq

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Date:	Thu, 23 Feb 2012 12:56:34 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Milton Miller <miltonm@....com>,
	Rob Herring <rob.herring@...xeda.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 22/25] irq_domain/x86: Convert x86 (embedded) to use
 common irq_domain

On Wed, Feb 1, 2012 at 11:06 AM, Grant Likely <grant.likely@...retlab.ca> wrote:
> On Wed, Feb 1, 2012 at 7:17 AM, Sebastian Andrzej Siewior
> <bigeasy@...utronix.de> wrote:
>> * Grant Likely | 2012-01-30 12:58:42 [-0700]:
>>
>>>Ugh.  This isn't easy.  The legacy mapping really needs all the
>>
>> Feel free to merge this patch. I don't have the time to look at this now
>> so I take a look at the ioapic later.
>
> There's no rush here.  I can leave it as-is with IRQ_DOMAIN turned off
> for x86 for now.

Turns out I have to enable IRQ_DOMAIN for x86 because the TI TWL4030
driver needs it.  I do need to apply this patch.  Until something
better can be implemented, can I change ioapic_add_ofnode() so that it
allocates all irq_descs immediately.  It's not ideal, but every other
approach I've looked at results in nasty hacks.

Looking at the ioapic code, it appears to handle preallocated
irq_descs gracefully.

Does adding this loop help (apologies if it is whitespace damaged, I
cut&paste it):

diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index 3ae2ced..89c1310 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -345,7 +345,7 @@ const struct irq_domain_ops ioapic_irq_domain_ops = {
 static void __init ioapic_add_ofnode(struct device_node *np)
 {
 	struct resource r;
-	int i, ret;
+	int i, j, ret;

 	ret = of_address_to_resource(np, 0, &r);
 	if (ret) {
@@ -361,6 +361,14 @@ static void __init ioapic_add_ofnode(struct
device_node *np)

 			gsi_cfg = mp_ioapic_gsi_routing(i);

+			/*
+			 * Preallocate irq_descs so that the legacy mapping
+			 * works, but don't set them up.
+			 * io_apic_setup_irq_pin_once() will finish the set up.
+			 */
+			for (j = 0; j < 32; j++)
+				irq_alloc_desc_at(gsi_cfg->gsi_base + j,
+						  cpu_to_node(0));
 			id = irq_domain_add_legacy(np, 32, gsi_cfg->gsi_base, 0,
 						   &ioapic_irq_domain_ops,
 						   (void*)i);


g.
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