]> pilppa.com Git - linux-2.6-omap-h63xx.git/commitdiff
rtc: fall back to requesting only the ports we actually use
authorBjorn Helgaas <bjorn.helgaas@hp.com>
Thu, 15 Nov 2007 00:59:57 +0000 (16:59 -0800)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Thu, 15 Nov 2007 02:45:41 +0000 (18:45 -0800)
Firmware like PNPBIOS or ACPI can report the address space consumed by the
RTC.  The actual space consumed may be less than the size (RTC_IO_EXTENT)
assumed by the RTC driver.

The PNP core doesn't request resources yet, but I'd like to make it do so.
If/when it does, the RTC_IO_EXTENT request may fail, which prevents the RTC
driver from loading.

Since we only use the RTC index and data registers at RTC_PORT(0) and
RTC_PORT(1), we can fall back to requesting just enough space for those.

If the PNP core requests resources, this results in typical I/O port usage
like this:

    0070-0073 : 00:06 <-- PNP device 00:06 responds to 70-73
      0070-0071 : rtc <-- RTC driver uses only 70-71

instead of the current:

    0070-0077 : rtc <-- RTC_IO_EXTENT == 8

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/char/rtc.c
include/linux/mc146818rtc.h

index a162e1b3d5d3a1dc1a327bd965b4ce9449f727b8..0c66b802736a10540bca3ed9d7ef34f5b0208b4a 100644 (file)
@@ -918,12 +918,29 @@ static const struct file_operations rtc_proc_fops = {
 };
 #endif
 
+static resource_size_t rtc_size;
+
+static struct resource * __init rtc_request_region(resource_size_t size)
+{
+       struct resource *r;
+
+       if (RTC_IOMAPPED)
+               r = request_region(RTC_PORT(0), size, "rtc");
+       else
+               r = request_mem_region(RTC_PORT(0), size, "rtc");
+
+       if (r)
+               rtc_size = size;
+
+       return r;
+}
+
 static void rtc_release_region(void)
 {
        if (RTC_IOMAPPED)
-               release_region(RTC_PORT(0), RTC_IO_EXTENT);
+               release_region(RTC_PORT(0), rtc_size);
        else
-               release_mem_region(RTC_PORT(0), RTC_IO_EXTENT);
+               release_mem_region(RTC_PORT(0), rtc_size);
 }
 
 static int __init rtc_init(void)
@@ -976,10 +993,17 @@ found:
        }
 no_irq:
 #else
-       if (RTC_IOMAPPED)
-               r = request_region(RTC_PORT(0), RTC_IO_EXTENT, "rtc");
-       else
-               r = request_mem_region(RTC_PORT(0), RTC_IO_EXTENT, "rtc");
+       r = rtc_request_region(RTC_IO_EXTENT);
+
+       /*
+        * If we've already requested a smaller range (for example, because
+        * PNPBIOS or ACPI told us how the device is configured), the request
+        * above might fail because it's too big.
+        *
+        * If so, request just the range we actually use.
+        */
+       if (!r)
+               r = rtc_request_region(RTC_IO_EXTENT_USED);
        if (!r) {
 #ifdef RTC_IRQ
                rtc_has_irq = 0;
index 580b3f4956ee260b551850d157f1f1b3992a5429..2f4e957af6568990944e0656546fcdba9a8faf3a 100644 (file)
@@ -109,8 +109,11 @@ struct cmos_rtc_board_info {
 #ifndef ARCH_RTC_LOCATION      /* Override by <asm/mc146818rtc.h>? */
 
 #define RTC_IO_EXTENT  0x8
+#define RTC_IO_EXTENT_USED     0x2
 #define RTC_IOMAPPED   1       /* Default to I/O mapping. */
 
+#else
+#define RTC_IO_EXTENT_USED      RTC_IO_EXTENT
 #endif /* ARCH_RTC_LOCATION */
 
 #endif /* _MC146818RTC_H */