rtc-cmos: export second NVRAM bank

Teach rtc-cmos about the second bank of registers found on most modern x86
systems, giving access to 128 bytes more NVRAM.

This version only sees that extra NVRAM when both register banks are
provided as part of *one* PNP resource.  Since BIOS on some systems
presents them using two IO resources, and nothing merges them, this can't
always show all the NVRAM.  (We're supposed to be able to use PNP id
PNP0b01 too, but BIOS tables doesn't often seem to use that particular
option.)
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-cmos.c

@@ -143,6 +143,43 @@ static inline int hpet_unregister_irq_handler(irq_handler_t handler)
 
 /*----------------------------------------------------------------*/
 
+#ifdef RTC_PORT
+
+/* Most newer x86 systems have two register banks, the first used
+ * for RTC and NVRAM and the second only for NVRAM.  Caller must
+ * own rtc_lock ... and we won't worry about access during NMI.
+ */
+#define can_bank2	true
+
+static inline unsigned char cmos_read_bank2(unsigned char addr)
+{
+	outb(addr, RTC_PORT(2));
+	return inb(RTC_PORT(3));
+}
+
+static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
+{
+	outb(addr, RTC_PORT(2));
+	outb(val, RTC_PORT(2));
+}
+
+#else
+
+#define can_bank2	false
+
+static inline unsigned char cmos_read_bank2(unsigned char addr)
+{
+	return 0;
+}
+
+static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
+{
+}
+
+#endif
+
+/*----------------------------------------------------------------*/
+
 static int cmos_read_time(struct device *dev, struct rtc_time *t)
 {
 	/* REVISIT:  if the clock has a "century" register, use
@@ -491,12 +528,21 @@ cmos_nvram_read(struct kobject *kobj, struct bin_attribute *attr,
 
 	if (unlikely(off >= attr->size))
 		return 0;
+	if (unlikely(off < 0))
+		return -EINVAL;
 	if ((off + count) > attr->size)
 		count = attr->size - off;
 
+	off += NVRAM_OFFSET;
 	spin_lock_irq(&rtc_lock);
-	for (retval = 0, off += NVRAM_OFFSET; count--; retval++, off++)
+	for (retval = 0; count; count--, off++, retval++) {
+		if (off < 128)
 			*buf++ = CMOS_READ(off);
+		else if (can_bank2)
+			*buf++ = cmos_read_bank2(off);
+		else
+			break;
+	}
 	spin_unlock_irq(&rtc_lock);
 
 	return retval;
@@ -512,6 +558,8 @@ cmos_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
 	cmos = dev_get_drvdata(container_of(kobj, struct device, kobj));
 	if (unlikely(off >= attr->size))
 		return -EFBIG;
+	if (unlikely(off < 0))
+		return -EINVAL;
 	if ((off + count) > attr->size)
 		count = attr->size - off;
 
@@ -520,15 +568,20 @@ cmos_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
 	 * here.  If userspace is smart enough to know what fields of
 	 * NVRAM to update, updating checksums is also part of its job.
 	 */
+	off += NVRAM_OFFSET;
 	spin_lock_irq(&rtc_lock);
-	for (retval = 0, off += NVRAM_OFFSET; count--; retval++, off++) {
+	for (retval = 0; count; count--, off++, retval++) {
 		/* don't trash RTC registers */
 		if (off == cmos->day_alrm
 				|| off == cmos->mon_alrm
 				|| off == cmos->century)
 			buf++;
-		else
+		else if (off < 128)
 			CMOS_WRITE(*buf++, off);
+		else if (can_bank2)
+			cmos_write_bank2(*buf++, off);
+		else
+			break;
 	}
 	spin_unlock_irq(&rtc_lock);
 
@@ -631,8 +684,8 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 
 	/* Heuristic to deduce NVRAM size ... do what the legacy NVRAM
 	 * driver did, but don't reject unknown configs.   Old hardware
-	 * won't address 128 bytes, and for now we ignore the way newer
-	 * chips can address 256 bytes (using two more i/o ports).
+	 * won't address 128 bytes.  Newer chips have multiple banks,
+	 * though they may not be listed in one I/O resource.
 	 */
 #if	defined(CONFIG_ATARI)
 	address_space = 64;
@@ -642,6 +695,8 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 #warning Assuming 128 bytes of RTC+NVRAM address space, not 64 bytes.
 	address_space = 128;
 #endif
+	if (can_bank2 && ports->end > (ports->start + 1))
+		address_space = 256;
 
 	/* For ACPI systems extension info comes from the FADT.  On others,
 	 * board specific setup provides it as appropriate.  Systems where
@@ -740,7 +795,7 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 		goto cleanup2;
 	}
 
-	pr_info("%s: alarms up to one %s%s%s\n",
+	pr_info("%s: alarms up to one %s%s, %zd bytes nvram, %s irqs\n",
 			cmos_rtc.rtc->dev.bus_id,
 			is_valid_irq(rtc_irq)
 				?  (cmos_rtc.mon_alrm
@@ -749,6 +804,7 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 						? "month" : "day"))
 				: "no",
 			cmos_rtc.century ? ", y3k" : "",
+			nvram.size,
 			is_hpet_enabled() ? ", hpet irqs" : "");
 
 	return 0;