drivers/clocksource/hyper-v: non ACPI support in hyperv clock

Add a placeholder function for the hv_setup_stimer0_irq API to accommodate
systems without ACPI support. Since this function is not utilized on
x86/x64 systems and non-ACPI support is only intended for x86/x64 systems,
a placeholder function is sufficient for now and can be improved upon if
necessary in the future.
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1679298460-11855-2-git-send-email-ssengar@linux.microsoft.comSigned-off-by: Wei Liu <wei.liu@kernel.org>

drivers/clocksource/hyperv_timer.c

@@ -49,7 +49,7 @@ static bool direct_mode_enabled;
 
 static int stimer0_irq = -1;
 static int stimer0_message_sint;
-static DEFINE_PER_CPU(long, stimer0_evt);
+static __maybe_unused DEFINE_PER_CPU(long, stimer0_evt);
 
 /*
  * Common code for stimer0 interrupts coming via Direct Mode or
@@ -68,7 +68,7 @@ EXPORT_SYMBOL_GPL(hv_stimer0_isr);
  * stimer0 interrupt handler for architectures that support
  * per-cpu interrupts, which also implies Direct Mode.
  */
-static irqreturn_t hv_stimer0_percpu_isr(int irq, void *dev_id)
+static irqreturn_t __maybe_unused hv_stimer0_percpu_isr(int irq, void *dev_id)
 {
 	hv_stimer0_isr();
 	return IRQ_HANDLED;
@@ -196,6 +196,7 @@ void __weak hv_remove_stimer0_handler(void)
 {
 };
 
+#ifdef CONFIG_ACPI
 /* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */
 static int hv_setup_stimer0_irq(void)
 {
@@ -230,6 +231,16 @@ static void hv_remove_stimer0_irq(void)
 		stimer0_irq = -1;
 	}
 }
+#else
+static int hv_setup_stimer0_irq(void)
+{
+	return 0;
+}
+
+static void hv_remove_stimer0_irq(void)
+{
+}
+#endif
 
 /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
 int hv_stimer_alloc(bool have_percpu_irqs)