From: Hanjun Guo <redacted>

Adding ACPI support for platform MSI, we need to retrieve the
dev id in ACPI way instead of device tree, we already have
a well formed function its_pmsi_prepare() to get the dev id
but it's OF dependent, so collect OF related code and put them
into a single function to make its_pmsi_prepare() more friendly
to ACPI later.

Signed-off-by: Hanjun Guo <redacted>
Tested-by: Sinan Kaya <redacted>
Cc: Marc Zyngier <redacted>
Cc: Lorenzo Pieralisi <redacted>
Cc: Tomasz Nowicki <redacted>
Cc: Thomas Gleixner <redacted>
---
  drivers/irqchip/irq-gic-v3-its-platform-msi.c | 23 ++++++++++++++++-------
  1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its-platform-msi.c b/drivers/irqchip/irq-gic-v3-its-platform-msi.c
index 470b4aa..3c94278 100644
--- a/drivers/irqchip/irq-gic-v3-its-platform-msi.c
+++ b/drivers/irqchip/irq-gic-v3-its-platform-msi.c

@@ -24,15 +24,11 @@
  	.name			= "ITS-pMSI",
  };
  
-static int its_pmsi_prepare(struct irq_domain *domain, struct device *dev,
-			    int nvec, msi_alloc_info_t *info)
+static int of_pmsi_get_dev_id(struct irq_domain *domain, struct device *dev,
+				  u32 *dev_id)
  {
-	struct msi_domain_info *msi_info;
-	u32 dev_id;
  	int ret, index = 0;
  
-	msi_info = msi_get_domain_info(domain->parent);
-
  	/* Suck the DeviceID out of the msi-parent property */
  	do {
  		struct of_phandle_args args;

@@ -43,11 +39,24 @@ static int its_pmsi_prepare(struct irq_domain *domain, struct device *dev,
  		if (args.np == irq_domain_get_of_node(domain)) {
  			if (WARN_ON(args.args_count != 1))
  				return -EINVAL;
-			dev_id = args.args[0];
+			*dev_id = args.args[0];
  			break;
  		}
  	} while (!ret);
  
+	return ret;
+}
+
+static int its_pmsi_prepare(struct irq_domain *domain, struct device *dev,
+			    int nvec, msi_alloc_info_t *info)
+{
+	struct msi_domain_info *msi_info;
+	u32 dev_id;
+	int ret;
+
+	msi_info = msi_get_domain_info(domain->parent);
+
+	ret = of_pmsi_get_dev_id(domain, dev, &dev_id);
  	if (ret)
  		return ret;