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rtc: fall back to requesting only the ports we actually use

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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>
This commit is contained in:
Bjorn Helgaas 2007-11-14 16:59:57 -08:00 committed by Linus Torvalds
parent 4c06be10c7
commit 9626f1f117
2 changed files with 33 additions and 6 deletions
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36
drivers/char/rtc.c
View 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;

3
include/linux/mc146818rtc.h
View 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 */