[PATCH v2 2/2] rtc: provide an emulated RTC
Heinrich Schuchardt
xypron.glpk at gmx.de
Mon Oct 26 20:18:08 CET 2020
On 26.10.20 16:31, Grant Likely wrote:
> On Mon, Oct 26, 2020 at 3:30 PM Grant Likely <grant.likely at secretlab.ca> wrote:
>>
>> On Sun, Oct 25, 2020 at 7:13 AM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>>
>>> On a board without hardware clock this software real time clock can be
>>> used. The build time is used to initialize the RTC. So you will have
>>> to adjust the time either manually using the 'date' command or use
>>> the 'sntp' to update the RTC with the time from a network time server.
>>> See CONFIG_CMD_SNTP and CONFIG_BOOTP_NTPSERVER. The RTC time is
>>> advanced according to CPU ticks.
>>>
>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>
>> Looks good to me, and tested on RockPro64 w/ UEFI SCT.
>>
>> Tested-by: Grant Likely <grant.likely at arm.com>
>
> One thought: Can this be automatically enabled if no other RTC driver
> is configured in?
* This RTC does not show the correct time unless you use SNTP to set it.
* There is no need for an RTC to boot an OS.
* Many board maintainers struggle with the size of there U-Boot binary.
So it does not make sense to me to enable this driver as fallback by
default.
Best regards
Heinrich
>
> g.
>
>>
>> g.
>>
>>> ---
>>> v2:
>>> more elaborate Kconfig message
>>> adjust device name properties
>>> use build time as initial time
>>> ---
>>> MAINTAINERS | 1 +
>>> drivers/rtc/Kconfig | 11 ++++++
>>> drivers/rtc/Makefile | 1 +
>>> drivers/rtc/emul_rtc.c | 80 ++++++++++++++++++++++++++++++++++++++++++
>>> 4 files changed, 93 insertions(+)
>>> create mode 100644 drivers/rtc/emul_rtc.c
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index fc4fad46ee..a98e0c5b76 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -678,6 +678,7 @@ S: Maintained
>>> T: git https://gitlab.denx.de/u-boot/custodians/u-boot-efi.git
>>> F: doc/api/efi.rst
>>> F: doc/uefi/*
>>> +F: drivers/rtc/emul_rtc.c
>>> F: include/capitalization.h
>>> F: include/charset.h
>>> F: include/cp1250.h
>>> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
>>> index 63662001c2..d06d272e14 100644
>>> --- a/drivers/rtc/Kconfig
>>> +++ b/drivers/rtc/Kconfig
>>> @@ -63,6 +63,17 @@ config RTC_DS3232
>>> Support for Dallas Semiconductor (now Maxim) DS3232 compatible
>>> Real Time Clock devices.
>>>
>>> +config RTC_EMULATION
>>> + bool "Enable emulated RTC"
>>> + depends on DM_RTC
>>> + help
>>> + On a board without hardware clock this software real time clock can be
>>> + used. The build time is used to initialize the RTC. So you will have
>>> + to adjust the time either manually using the 'date' command or use
>>> + the 'sntp' to update the RTC with the time from a network time server.
>>> + See CONFIG_CMD_SNTP and CONFIG_BOOTP_NTPSERVER. The RTC time is
>>> + advanced according to CPU ticks.
>>> +
>>> config RTC_ISL1208
>>> bool "Enable ISL1208 driver"
>>> depends on DM_RTC
>>> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
>>> index 12eb449583..ef66dc4bf0 100644
>>> --- a/drivers/rtc/Makefile
>>> +++ b/drivers/rtc/Makefile
>>> @@ -22,6 +22,7 @@ obj-$(CONFIG_RTC_DS164x) += ds164x.o
>>> obj-$(CONFIG_RTC_DS174x) += ds174x.o
>>> obj-$(CONFIG_RTC_DS3231) += ds3231.o
>>> obj-$(CONFIG_RTC_DS3232) += ds3232.o
>>> +obj-$(CONFIG_RTC_EMULATION) += emul_rtc.o
>>> obj-$(CONFIG_RTC_FTRTC010) += ftrtc010.o
>>> obj-$(CONFIG_SANDBOX) += i2c_rtc_emul.o
>>> obj-$(CONFIG_RTC_IMXDI) += imxdi.o
>>> diff --git a/drivers/rtc/emul_rtc.c b/drivers/rtc/emul_rtc.c
>>> new file mode 100644
>>> index 0000000000..c98c24bbb3
>>> --- /dev/null
>>> +++ b/drivers/rtc/emul_rtc.c
>>> @@ -0,0 +1,80 @@
>>> +// SPDX-License-Identifier: GPL-2.0+
>>> +/*
>>> + * Copyright 2020, Heinrich Schuchardt <xypron.glpk at gmx.de>
>>> + *
>>> + * This driver emulates a real time clock based on timer ticks.
>>> + */
>>> +
>>> +#include <common.h>
>>> +#include <div64.h>
>>> +#include <dm.h>
>>> +#include <generated/timestamp_autogenerated.h>
>>> +#include <rtc.h>
>>> +
>>> +/**
>>> + * struct emul_rtc - private data for emulated RTC driver
>>> + */
>>> +struct emul_rtc {
>>> + /**
>>> + * @offset_us: microseconds from 1970-01-01 to timer_get_us() base
>>> + */
>>> + u64 offset_us;
>>> + /**
>>> + * @isdst: daylight saving time
>>> + */
>>> + int isdst;
>>> +};
>>> +
>>> +static int emul_rtc_get(struct udevice *dev, struct rtc_time *time)
>>> +{
>>> + struct emul_rtc *priv = dev_get_priv(dev);
>>> + u64 now;
>>> +
>>> + if (!priv->offset_us) {
>>> + /* Use the build date as initial time */
>>> + priv->offset_us = U_BOOT_EPOCH * 1000000ULL - timer_get_us();
>>> + priv->isdst = -1;
>>> + }
>>> +
>>> + now = timer_get_us() + priv->offset_us;
>>> + do_div(now, 1000000);
>>> + rtc_to_tm(now, time);
>>> + time->tm_isdst = priv->isdst;
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int emul_rtc_set(struct udevice *dev, const struct rtc_time *time)
>>> +{
>>> + struct emul_rtc *priv = dev_get_priv(dev);
>>> +
>>> + if (time->tm_year < 1970)
>>> + return -EINVAL;
>>> +
>>> + priv->offset_us = rtc_mktime(time) * 1000000ULL - timer_get_us();
>>> +
>>> + if (time->tm_isdst > 0)
>>> + priv->isdst = 1;
>>> + else if (time->tm_isdst < 0)
>>> + priv->isdst = -1;
>>> + else
>>> + priv->isdst = 0;
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static const struct rtc_ops emul_rtc_ops = {
>>> + .get = emul_rtc_get,
>>> + .set = emul_rtc_set,
>>> +};
>>> +
>>> +U_BOOT_DRIVER(rtc_emul) = {
>>> + .name = "rtc_emul",
>>> + .id = UCLASS_RTC,
>>> + .ops = &emul_rtc_ops,
>>> + .priv_auto_alloc_size = sizeof(struct emul_rtc),
>>> +};
>>> +
>>> +U_BOOT_DEVICE(rtc_emul) = {
>>> + .name = "rtc_emul",
>>> +};
>>> --
>>> 2.28.0
>>>
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