drm/msm: Get irq number within kms driver itself

The driver gets the irq number using platform_get_irq on the main kms
platform device. This works fine since both MDP4 and MDP5 currently
have a flat device hierarchy. The platform device tied with the
drm_device points to the MDP DT node in both cases.

This won't work when MDP5 supports a tree-like hierarchy. In this
case, the platform device tied to the top level drm_device is the
MDSS DT node, and the irq we need for KMS is the one generated by
MDP5, not MDSS.

Get the irq number from the MDP4/5 kms driver itself. Each driver
can later provide the irq number based on what device hierarchy it
uses.

While we're at it, call drm_irq_install only when we have a valid KMS
driver.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c

@@ -580,7 +580,7 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
 	struct msm_kms *kms = NULL;
 	struct msm_mmu *mmu;
 	uint32_t major, minor;
-	int i, ret;
+	int irq, i, ret;
 
 	mdp5_kms = kzalloc(sizeof(*mdp5_kms), GFP_KERNEL);
 	if (!mdp5_kms) {
@@ -610,6 +610,15 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
 		goto fail;
 	}
 
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		ret = irq;
+		dev_err(dev->dev, "failed to get irq: %d\n", ret);
+		goto fail;
+	}
+
+	kms->irq = irq;
+
 	mdp5_kms->vdd = devm_regulator_get(&pdev->dev, "vdd");
 	if (IS_ERR(mdp5_kms->vdd)) {
 		ret = PTR_ERR(mdp5_kms->vdd);