rtc: cmos: Drop PNP device support

Previous changes effectively prevented PNP devices from being created
for the CMOS RTC on x86 with ACPI.

Although in principle a CMOS RTC PNP device may exist on an x86 system
without ACPI (that is, an x86 system where there is no ACPI at all, not
one booted with ACPI disabled), such systems were there in the field ~30
years ago and most likely they would not be able to run a contemporary
Linux kernel.

For the above reasons, drop the PNP device support from the rtc-cmos
driver.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://patch.msgid.link/2355012.iZASKD2KPV@rafael.j.wysocki

Author: rafaeljw

drivers/rtc/rtc-cmos.c

@@ -1370,85 +1370,6 @@ static int __maybe_unused cmos_resume(struct device *dev)
 
 static SIMPLE_DEV_PM_OPS(cmos_pm_ops, cmos_suspend, cmos_resume);
 
-/*----------------------------------------------------------------*/
-
-/* On non-x86 systems, a "CMOS" RTC lives most naturally on platform_bus.
- * ACPI systems always list these as PNPACPI devices, and pre-ACPI PCs
- * probably list them in similar PNPBIOS tables; so PNP is more common.
- *
- * We don't use legacy "poke at the hardware" probing.  Ancient PCs that
- * predate even PNPBIOS should set up platform_bus devices.
- */
-
-#ifdef	CONFIG_PNP
-
-#include <linux/pnp.h>
-
-static int cmos_pnp_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
-{
-	int irq;
-
-	if (pnp_port_start(pnp, 0) == 0x70 && !pnp_irq_valid(pnp, 0)) {
-		irq = 0;
-#ifdef CONFIG_X86
-		/* Some machines contain a PNP entry for the RTC, but
-		 * don't define the IRQ. It should always be safe to
-		 * hardcode it on systems with a legacy PIC.
-		 */
-		if (nr_legacy_irqs())
-			irq = RTC_IRQ;
-#endif
-	} else {
-		irq = pnp_irq(pnp, 0);
-	}
-
-	return cmos_do_probe(&pnp->dev, pnp_get_resource(pnp, IORESOURCE_IO, 0), irq);
-}
-
-static void cmos_pnp_remove(struct pnp_dev *pnp)
-{
-	cmos_do_remove(&pnp->dev);
-}
-
-static void cmos_pnp_shutdown(struct pnp_dev *pnp)
-{
-	struct device *dev = &pnp->dev;
-	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
-
-	if (system_state == SYSTEM_POWER_OFF) {
-		int retval = cmos_poweroff(dev);
-
-		if (cmos_aie_poweroff(dev) < 0 && !retval)
-			return;
-	}
-
-	cmos_do_shutdown(cmos->irq);
-}
-
-static const struct pnp_device_id rtc_ids[] = {
-	{ .id = "PNP0b00", },
-	{ .id = "PNP0b01", },
-	{ .id = "PNP0b02", },
-	{ },
-};
-MODULE_DEVICE_TABLE(pnp, rtc_ids);
-
-static struct pnp_driver cmos_pnp_driver = {
-	.name		= driver_name,
-	.id_table	= rtc_ids,
-	.probe		= cmos_pnp_probe,
-	.remove		= cmos_pnp_remove,
-	.shutdown	= cmos_pnp_shutdown,
-
-	/* flag ensures resume() gets called, and stops syslog spam */
-	.flags		= PNP_DRIVER_RES_DO_NOT_CHANGE,
-	.driver		= {
-			.pm = &cmos_pm_ops,
-	},
-};
-
-#endif	/* CONFIG_PNP */
-
 #ifdef CONFIG_OF
 static const struct of_device_id of_cmos_match[] = {
 	{
@@ -1543,45 +1464,27 @@ static struct platform_driver cmos_platform_driver = {
 	}
 };
 
-#ifdef CONFIG_PNP
-static bool pnp_driver_registered;
-#endif
 static bool platform_driver_registered;
 
 static int __init cmos_init(void)
 {
-	int retval = 0;
+	int retval;
 
-#ifdef	CONFIG_PNP
-	retval = pnp_register_driver(&cmos_pnp_driver);
-	if (retval == 0)
-		pnp_driver_registered = true;
-#endif
+	if (cmos_rtc.dev)
+		return 0;
 
-	if (!cmos_rtc.dev) {
-		retval = platform_driver_probe(&cmos_platform_driver,
-					       cmos_platform_probe);
-		if (retval == 0)
-			platform_driver_registered = true;
-	}
+	retval = platform_driver_probe(&cmos_platform_driver, cmos_platform_probe);
+	if (retval)
+		return retval;
 
-	if (retval == 0)
-		return 0;
+	platform_driver_registered = true;
 
-#ifdef	CONFIG_PNP
-	if (pnp_driver_registered)
-		pnp_unregister_driver(&cmos_pnp_driver);
-#endif
-	return retval;
+	return 0;
 }
 module_init(cmos_init);
 
 static void __exit cmos_exit(void)
 {
-#ifdef	CONFIG_PNP
-	if (pnp_driver_registered)
-		pnp_unregister_driver(&cmos_pnp_driver);
-#endif
 	if (platform_driver_registered)
 		platform_driver_unregister(&cmos_platform_driver);
 }