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Commit 9626f1f1 authored by Bjorn Helgaas's avatar Bjorn Helgaas Committed by Linus Torvalds
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rtc: fall back to requesting only the ports we actually use 



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: default avatarBjorn 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4c06be10

drivers/char/rtc.c

+30 −6
Original line number Diff line number Diff line
@@ -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 @@ static int __init rtc_init(void) 
	}

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;

include/linux/mc146818rtc.h

+3 −0
Original line number Diff line number Diff line
@@ -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 */