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x86/RTC: introduce a new generic rtc_ops for x86

RFC PATCH In review Feng Tang 2 participants 3 messages Aug 11, 2009 – Aug 12, 2009

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Feng Tang

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RFC PATCH 1/1 x86/RTC: introduce a new generic rtc_ops for x86

Please help to review this patch, thanks!

It is generated against kernel 2.6.31-rc5

- Feng

Quoted 1 line

From a8ee2a78bcc1df57f2f43ff526269d69a2801a64 Mon Sep 17 00:00:00 2001

From: Feng Tang <[email protected]>
Date: Wed, 17 Jun 2009 10:31:17 +0800
Subject: [PATCH] x86/RTC: introduce a new generic rtc_ops for x86

System time keeping needs get_wallclock/set_wallclock supports, currently this support comes from Motorola 146818 like RTC device or EFI, or even virtualization, but in the future, there will be other x86 platforms which don't have these options and have their own RTC devices other than the 146818. So a more generic structure is needed to support all platforms' need

This patch adds a arch_rtc_ops structure, which only has 2 API pointers of get/set wall clock, each platform can register its own desired RTC ops to be the one to use

Current patch only modifies the rtc.c and efi.c to incorporate this change, further on we can think about to use it for the paravirt code, which could make the asm/time.h much cleaner

Signed-off-by Feng Tang <[email protected]>
---
 arch/x86/include/asm/time.h |   45 +++++++++++-------------------------------
 arch/x86/kernel/efi.c       |   12 +++++++++++
 arch/x86/kernel/rtc.c       |    5 ++++
 3 files changed, 29 insertions(+), 33 deletions(-)
arch/x86/include/asm/time.h +12 -33
index 50c733a..3665a9c 100644
@@ -1,53 +1,32 @@
 #ifndef _ASM_X86_TIME_H
 #define _ASM_X86_TIME_H
 
+#include <asm/mc146818rtc.h>
+
 extern void hpet_time_init(void);
+extern void time_init(void);
 
-#include <asm/mc146818rtc.h>
-#ifdef CONFIG_X86_32
-#include <linux/efi.h>
+struct arch_rtc_dev_ops {
+	unsigned long	(*get_wall_time)(void);
+	int		(*set_wall_time)(unsigned long);
+};
+extern struct arch_rtc_dev_ops *x86_rtc_ops;
 
 static inline unsigned long native_get_wallclock(void)
 {
-	unsigned long retval;
-
-	if (efi_enabled)
-		retval = efi_get_time();
-	else
-		retval = mach_get_cmos_time();
-
-	return retval;
+	return x86_rtc_ops->get_wall_time();
 }
 
 static inline int native_set_wallclock(unsigned long nowtime)
 {
-	int retval;
-
-	if (efi_enabled)
-		retval = efi_set_rtc_mmss(nowtime);
-	else
-		retval = mach_set_rtc_mmss(nowtime);
-
-	return retval;
+	return x86_rtc_ops->set_wall_time(nowtime);
 }
 
-#else
-extern void native_time_init_hook(void);
-
-static inline unsigned long native_get_wallclock(void)
-{
-	return mach_get_cmos_time();
-}
-
-static inline int native_set_wallclock(unsigned long nowtime)
+static inline void register_rtc_ops(struct arch_rtc_dev_ops *ops)
 {
-	return mach_set_rtc_mmss(nowtime);
+	x86_rtc_ops = ops;
 }
 
-#endif
-
-extern void time_init(void);
-
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else /* !CONFIG_PARAVIRT */
arch/x86/kernel/efi.c +12 -0
index 96f7ac0..67ec1a6 100644
@@ -224,6 +224,15 @@ unsigned long efi_get_time(void)
 		      eft.minute, eft.second);
 }
 
+static struct arch_rtc_dev_ops efi_rtc_ops = {
+	.get_wall_time = efi_get_time,
+	.set_wall_time = efi_set_rtc_mmss,
+};
+
+static void efi_wall_time_init(void)
+{
+	register_rtc_ops(&efi_rtc_ops);
+}
 /*
  * Tell the kernel about the EFI memory map.  This might include
  * more than the max 128 entries that can fit in the e820 legacy

@@ -453,6 +462,9 @@ void __init efi_init(void)
 	if (add_efi_memmap)
 		do_add_efi_memmap();
 
+	/* use efi to get/set hw time */
+	efi_wall_time_init();
+
 	/* Setup for EFI runtime service */
 	reboot_type = BOOT_EFI;
arch/x86/kernel/rtc.c +5 -0
index 5d465b2..b906a18 100644
@@ -200,6 +200,11 @@ unsigned long long native_read_tsc(void)
 }
 EXPORT_SYMBOL(native_read_tsc);
 
+struct arch_rtc_dev_ops rtc_ops = {
+	.get_wall_time = mach_get_cmos_time,
+	.set_wall_time = mach_set_rtc_mmss,
+};
+struct arch_rtc_dev_ops *x86_rtc_ops = &rtc_ops;
 
 static struct resource rtc_resources[] = {
 	[0] = {
Signature · 1 line
1.5.6.3
#1 lore raw
Quoted 44 lines · Feng Tang

Please help to review this patch, thanks!

It is generated against kernel 2.6.31-rc5

- Feng

From a8ee2a78bcc1df57f2f43ff526269d69a2801a64 Mon Sep 17 00:00:00 2001
From: Feng Tang <[email protected]>
Date: Wed, 17 Jun 2009 10:31:17 +0800
Subject: [PATCH] x86/RTC: introduce a new generic rtc_ops for x86

System time keeping needs get_wallclock/set_wallclock supports, currently this support comes from Motorola 146818 like RTC device or EFI, or even virtualization, but in the future, there will be other x86 platforms which don't have these options and have their own RTC devices other than the 146818. So a more generic structure is needed to support all platforms' need

This patch adds a arch_rtc_ops structure, which only has 2 API pointers of get/set wall clock, each platform can register its own desired RTC ops to be the one to use

Current patch only modifies the rtc.c and efi.c to incorporate this change, further on we can think about to use it for the paravirt code, which could make the asm/time.h much cleaner

Signed-off-by Feng Tang <[email protected]>
---
 arch/x86/include/asm/time.h |   45 +++++++++++-------------------------------
 arch/x86/kernel/efi.c       |   12 +++++++++++
 arch/x86/kernel/rtc.c       |    5 ++++
 3 files changed, 29 insertions(+), 33 deletions(-)
arch/x86/include/asm/time.h +2 -0
index 50c733a..3665a9c 100644
@@ -1,53 +1,32 @@
 #ifndef _ASM_X86_TIME_H
 #define _ASM_X86_TIME_H
 
+#include <asm/mc146818rtc.h>
+
 extern void hpet_time_init(void);

arch/x86/include/asm/time.h line 13

Quoted 10 lines
arch/x86/include/asm/time.h +6 -3
+extern void time_init(void);
 
-#include <asm/mc146818rtc.h>
-#ifdef CONFIG_X86_32
-#include <linux/efi.h>
+struct arch_rtc_dev_ops {
+	unsigned long	(*get_wall_time)(void);
+	int		(*set_wall_time)(unsigned long);
+};
+extern struct arch_rtc_dev_ops *x86_rtc_ops;

looks like the right direction at first glance. What's the management interface around the driver (there's none at the moment)? Set up at early boot time and never changed afterwards?

Have you looked at other architectures (MIPS, ARM, etc.) to see how they abstracted away their RTC functionality?

Ingo

author
#2 lore raw
Quoted 4 lines · On Tue, 11 Aug 2009 16:45:29 +0800 Ingo Molnar <[email protected]> wrote:
Quoted 4 lines
arch/x86/include/asm/time.h +1 -3
-#include <asm/mc146818rtc.h>
-#ifdef CONFIG_X86_32
-#include <linux/efi.h>
+struct arch_rtc_dev_ops {
Quoted 8 lines

arch/x86/include/asm/time.h line 13

Quoted 4 lines
arch/x86/include/asm/time.h +4 -0
+	unsigned long	(*get_wall_time)(void);
+	int		(*set_wall_time)(unsigned long);
+};
+extern struct arch_rtc_dev_ops *x86_rtc_ops;

looks like the right direction at first glance. What's the management interface around the driver (there's none at the moment)? Set up at early boot time and never changed afterwards?

Currently there is no management interface around it, the structure works the way like x86_quirks, as EFI/mc146818 are kindly fixed and can't be dynamically detected.

Quoted 3 lines

Have you looked at other architectures (MIPS, ARM, etc.) to see how they abstracted away their RTC functionality?

I did a quick look at other architectures, and didn't see a nice abstracted way for RTC.

In kernel early boot phase, read_persistent_clock() is called to get the HW time, x86 implements the API by calling get_wall_time(), but just a few other architectures implement their own read_persistent_clock() if they have rtc devices/services that could be accessed in early boot phase, like some of MIPS/PowerPC/s390...(ARM doesn't). So it would be difficult to ask all architectures to use the arch_rtc_dev_ops structure.

But as kernel needs the HW time anyway, some arch/platforms implements their rtc driver in drivers/rtc/ not in arch/.../kernel/, which will get HW time and set it to the system time in late boot phase using late_initcall

Thanks,
Feng

Quoted 2 lines

Ingo