This patch clarifies usage of irq_chip->startup() callback:
1. The "if (startup) startup(); else enabled();" code in setup_irq()
   is unnecessary, as startup() falls back to enabled() via
   default callbacks, set by irq_chip_set_defaults().
2. When using set_irq_chained_handler() the startup() was never called,
   which is not good at all... Fixed. And again - when startup() is not
   defined the call will fall back to enable() than to unmask() via
   default callbacks.
Signed-off-by: Pawel Moll <pawel.moll@st.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
                desc->status &= ~IRQ_DISABLED;
                desc->status |= IRQ_NOREQUEST | IRQ_NOPROBE;
                desc->depth = 0;
-               desc->chip->unmask(irq);
+               desc->chip->startup(irq);
        }
        spin_unlock_irqrestore(&desc->lock, flags);
 }
 
                if (!(desc->status & IRQ_NOAUTOEN)) {
                        desc->depth = 0;
                        desc->status &= ~IRQ_DISABLED;
-                       if (desc->chip->startup)
-                               desc->chip->startup(irq);
-                       else
-                               desc->chip->enable(irq);
+                       desc->chip->startup(irq);
                } else
                        /* Undo nested disables: */
                        desc->depth = 1;