Re: [PATCH] add rtc platform driver for EFI

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 9 Jan 2009 14:36:16 -0700 dann frazier <dannf@dannf.org> wrote:

> Munge Stephane Eranian's efirtc.c code into an rtc platform driver
>
> 
> ...
>
> index f0ebb34..9ed5ba0 100644
> --- a/arch/ia64/kernel/time.c
> +++ b/arch/ia64/kernel/time.c
> @@ -20,6 +20,7 @@
>  #include <linux/efi.h>
>  #include <linux/timex.h>
>  #include <linux/clocksource.h>
> +#include <linux/platform_device.h>
>  
>  #include <asm/machvec.h>
>  #include <asm/delay.h>
> @@ -405,6 +406,23 @@ static struct irqaction timer_irqaction = {
>  	.name =		"timer"
>  };
>  
> +struct platform_device rtc_efi_dev = {

static, please.

> +	.name = "rtc-efi",
> +	.id = -1,
> +};
> +
> +static int __init rtc_init(void)
> +{
> +	int ret;
> +	ret = platform_device_register(&rtc_efi_dev);
> +	if (ret < 0)
> +		printk(KERN_ERR "unable to register rtc device...\n");

we don't really need `ret'...

> +	/* not necessarily an error */
> +	return 0;
> +}
> +module_init(rtc_init);
> +
>  void __init
>  time_init (void)
>  {
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index 4ad831d..2cc8a9d 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -434,6 +434,16 @@ config RTC_DRV_DS1742
>  	  This driver can also be built as a module. If so, the module
>  	  will be called rtc-ds1742.
>  
> +config RTC_DRV_EFI
> +	tristate "EFI RTC"
> +	depends on IA64
> +	help
> +	  If you say yes here you will get support for the EFI
> +	  Real Time Clock.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called rtc-efi.
> +
>  config RTC_DRV_STK17TA8
>  	tristate "Simtek STK17TA8"
>  	depends on RTC_CLASS
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 9a4340d..09ae207 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -35,6 +35,7 @@ obj-$(CONFIG_RTC_DRV_DS1553)	+= rtc-ds1553.o
>  obj-$(CONFIG_RTC_DRV_DS1672)	+= rtc-ds1672.o
>  obj-$(CONFIG_RTC_DRV_DS1742)	+= rtc-ds1742.o
>  obj-$(CONFIG_RTC_DRV_DS3234)	+= rtc-ds3234.o
> +obj-$(CONFIG_RTC_DRV_EFI)	+= rtc-efi.o
>  obj-$(CONFIG_RTC_DRV_EP93XX)	+= rtc-ep93xx.o
>  obj-$(CONFIG_RTC_DRV_FM3130)	+= rtc-fm3130.o
>  obj-$(CONFIG_RTC_DRV_ISL1208)	+= rtc-isl1208.o
> diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
> new file mode 100644
> index 0000000..1e9607b
> --- /dev/null
> +++ b/drivers/rtc/rtc-efi.c
> @@ -0,0 +1,275 @@
> +/*
> + * rtc-efi: RTC Class Driver for EFI-based systems
> + *
> + * Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
> + *
> + * Author: dann frazier <dannf@hp.com>
> + * Based on efirtc.c by Stephane Eranian
> + *
> + *  This program is free software; you can redistribute  it and/or modify it
> + *  under  the terms of  the GNU General  Public License as published by the
> + *  Free Software Foundation;  either version 2 of the  License, or (at your
> + *  option) any later version.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/time.h>
> +#include <linux/platform_device.h>
> +
> +#include <linux/efi.h>
> +
> +#define EFI_ISDST (EFI_TIME_ADJUST_DAYLIGHT|EFI_TIME_IN_DAYLIGHT)
> +/*
> + * EFI Epoch is 1/1/1998
> + */
> +#define EFI_RTC_EPOCH		1998
> +
> +#define LEAP_YEAR(year) ((!(year % 4) && (year % 100)) || !(year % 400))
> +
> +struct efi_rtc {
> +	struct rtc_device *rtc;
> +	spinlock_t lock;
> +};

This never gets used?

> +static const unsigned short int __mon_yday[2][13] =
> +{

static const unsigned short __mon_yday[2][13] = {

please.

> +	/* Normal years.  */
> +	{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
> +	/* Leap years.  */
> +	{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
> +};

hm, I bet there are other places in the kernel where we use (or need)
that table. 

> +
> +/*
> + * returns day of the year [0-365]
> + */
> +static inline int
> +compute_yday(efi_time_t *eft)
> +{
> +	/* efi_time_t.month is in the [1-12] so, we need -1 */
> +	return rtc_year_days(eft->day - 1, eft->month - 1, eft->year);
> +}
> +/*
> + * returns day of the week [0-6] 0=Sunday
> + *
> + * Don't try to provide a year that's before 1998, please !
> + */
> +static int
> +compute_wday(efi_time_t *eft)
> +{
> +	int y;
> +	int ndays = 0;
> +
> +	if (eft->year < 1998) {
> +		printk(KERN_ERR "efirtc: EFI year < 1998, invalid date\n");
> +		return -1;
> +	}
> +
> +	for (y = EFI_RTC_EPOCH; y < eft->year; y++)
> +		ndays += 365 + (LEAP_YEAR(y) ? 1 : 0);
> +
> +	ndays += compute_yday(eft);
> +
> +	/*
> +	 * 4=1/1/1998 was a Thursday
> +	 */
> +	return (ndays + 4) % 7;
> +}
> +
> +static void
> +convert_to_efi_time(struct rtc_time *wtime, efi_time_t *eft)
> +{
> +

dd

> +	eft->year	= wtime->tm_year + 1900;
> +	eft->month	= wtime->tm_mon + 1;
> +	eft->day	= wtime->tm_mday;
> +	eft->hour	= wtime->tm_hour;
> +	eft->minute	= wtime->tm_min;
> +	eft->second 	= wtime->tm_sec;
> +	eft->nanosecond = 0;
> +	eft->daylight	= wtime->tm_isdst ? EFI_ISDST : 0;
> +	eft->timezone	= EFI_UNSPECIFIED_TIMEZONE;
> +}
> +
> +static void
> +convert_from_efi_time(efi_time_t *eft, struct rtc_time *wtime)
> +{
> +	memset(wtime, 0, sizeof(*wtime));
> +	wtime->tm_sec  = eft->second;
> +	wtime->tm_min  = eft->minute;
> +	wtime->tm_hour = eft->hour;
> +	wtime->tm_mday = eft->day;
> +	wtime->tm_mon  = eft->month - 1;
> +	wtime->tm_year = eft->year - 1900;
> +
> +	/* day of the week [0-6], Sunday=0 */
> +	wtime->tm_wday = compute_wday(eft);
> +
> +	/* day in the year [1-365]*/
> +	wtime->tm_yday = compute_yday(eft);
> +
> +
> +	switch (eft->daylight & EFI_ISDST) {
> +	case EFI_ISDST:
> +		wtime->tm_isdst = 1;
> +		break;
> +	case EFI_TIME_ADJUST_DAYLIGHT:
> +		wtime->tm_isdst = 0;
> +		break;
> +	default:
> +		wtime->tm_isdst = -1;
> +	}
> +}
> +
> +static int efi_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
> +{
> +	efi_time_t eft;
> +	efi_status_t status;
> +
> +	lock_kernel();
> +
> +	/*
> +	 * As of EFI v1.10, this call always returns an unsupported status
> +	 */
> +	status = efi.get_wakeup_time((efi_bool_t *)&wkalrm->enabled,
> +				     (efi_bool_t *)&wkalrm->pending, &eft);
> +
> +	unlock_kernel();

eek.  The patch adds a great pile of lock_kernel() calls.  Everyone
else is busily deleting them.

Can we not do this?

> +	if (status != EFI_SUCCESS)
> +		return -EINVAL;
> +
> +	convert_from_efi_time(&eft, &wkalrm->time);
> +
> +	return rtc_valid_tm(&wkalrm->time);
> +}
> +
>
> ...
>