usb: musb: core: add pm_runtime_irq_safe()

We need a pm_runtime_get_sync() call from
within musb_gadget_pullup() to make sure
registers are accessible at that time.

The problem is that musb_gadget_pullup() is
called with IRQs disabled and, because of that,
we need to tell pm_runtime that this pm_runtime_get_sync()
is IRQ safe.

We can simply add pm_runtime_irq_safe(), however, because
we need to make our read/write accessor function pointers
have been initialized before trying to use them. This means
that all pm_runtime initialization for musb_core needs to
be moved down so that when we call pm_runtime_irq_safe(),
the pm_runtime_get_sync() that it calls on the parent, won't
cause a crash due to NULL musb_read/write accessors.

Reported-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_core.c

@@ -1969,10 +1969,6 @@ musb_init_controller(struct device *dev, int nIrq, void __iomem *ctrl)
 		goto fail0;
 	}
 
-	pm_runtime_use_autosuspend(musb->controller);
-	pm_runtime_set_autosuspend_delay(musb->controller, 200);
-	pm_runtime_enable(musb->controller);
-
 	spin_lock_init(&musb->lock);
 	musb->board_set_power = plat->set_power;
 	musb->min_power = plat->min_power;
@@ -1991,6 +1987,12 @@ musb_init_controller(struct device *dev, int nIrq, void __iomem *ctrl)
 	musb_readl = musb_default_readl;
 	musb_writel = musb_default_writel;
 
+	/* We need musb_read/write functions initialized for PM */
+	pm_runtime_use_autosuspend(musb->controller);
+	pm_runtime_set_autosuspend_delay(musb->controller, 200);
+	pm_runtime_irq_safe(musb->controller);
+	pm_runtime_enable(musb->controller);
+
 	/* The musb_platform_init() call:
 	 *   - adjusts musb->mregs
 	 *   - sets the musb->isr