From: Neil Armstrong <narmstrong@baylibre.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: khilman@baylibre.com, carlo@caione.org, a.zummo@towertech.it,
alexandre.belloni@free-electrons.com,
linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, rtc-linux@googlegroups.com
Subject: Re: [RFC PATCH 2/3] rtc: Add Amlogic Virtual Wake RTC
Date: Thu, 3 Nov 2016 16:46:36 +0100 [thread overview]
Message-ID: <77aab6f0-e6a4-f0e2-2c08-7c545e8c07af@baylibre.com> (raw)
In-Reply-To: <20161103153647.GD25852@remoulade>
On 11/03/2016 04:36 PM, Mark Rutland wrote:
> On Thu, Nov 03, 2016 at 03:29:24PM +0100, Neil Armstrong wrote:
>> The Amlogic Meson GX SoCs uses a special register to store the
>> time in seconds to wakeup after a system suspend.
>
> Where does this register live, exactly? What IP block is it part of?
It's part of the Always-ON APB registers, there is no clear IP block here,
but it seems to be like a scratch register shared with the BL3 FW.
>
>> In order to be able to reuse the RTC wakealarm feature, this
>> driver implements a fake RTC device which uses the system time
>> to deduce a suspend delay.
>
> This sounds like an always-on oneshot timer device, not an RTC.
The register seems to never change, and it seems to be an indication for the
FW when it enters the suspend mode.
>
>> +static int meson_vrtc_read_time(struct device *dev, struct rtc_time *tm)
>> +{
>> + unsigned long local_time;
>> + struct timeval time;
>> +
>> + do_gettimeofday(&time);
>> + local_time = time.tv_sec - (sys_tz.tz_minuteswest * 60);
>> + rtc_time_to_tm(local_time, tm);
>> +
>> + return 0;
>> +}
>
> ... if this were a timer, you wouldn't need this hack.
Actually the vendor tree uses a 64bit running counter to provide this
but with a fixed start date.
>
>> +static int meson_vrtc_probe(struct platform_device *pdev)
>> +{
>> + struct meson_vrtc_data *vrtc;
>> + struct resource *res;
>> +
>> + vrtc = devm_kzalloc(&pdev->dev, sizeof(*vrtc), GFP_KERNEL);
>> + if (!vrtc)
>> + return -ENOMEM;
>> +
>> + vrtc->pdev = pdev;
>> +
>> + /* Alarm registers */
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + vrtc->io_alarm = devm_ioremap_resource(&pdev->dev, res);
>> + if (IS_ERR(vrtc->io_alarm))
>> + return PTR_ERR(vrtc->io_alarm);
>> +
>> + device_init_wakeup(&pdev->dev, 1);
>> +
>> + platform_set_drvdata(pdev, vrtc);
>> +
>> + vrtc->rtc = devm_rtc_device_register(&pdev->dev, "meson-vrtc",
>> + &meson_vrtc_ops, THIS_MODULE);
>> + if (IS_ERR(vrtc->rtc))
>> + return PTR_ERR(vrtc->rtc);
>> +
>> + return 0;
>> +}
>
> I see that no interrupt is described. How exactly does this wake the system
> from suspend? Is there some interrupt managed by FW for this, for example?
It seems to be managed by the BL3 FW. We have no details on the underlying implementation.
>
>> +static const struct of_device_id meson_vrtc_dt_match[] = {
>> + { .compatible = "amlogic,meson-vrtc"},
>
> There was no binding documentation in this patch series.
>
> Thanks,
> Mark.
>
next prev parent reply other threads:[~2016-11-03 15:46 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-03 14:29 [RFC PATCH 0/3] ARM64: meson-gxbb: Add support for system suspend Neil Armstrong
2016-11-03 14:29 ` [RFC PATCH 1/3] ARM64: meson: Add Amlogic Meson GX PM Suspend Neil Armstrong
2016-11-03 15:30 ` Mark Rutland
2016-11-03 21:53 ` Sudeep Holla
2016-11-04 9:13 ` Neil Armstrong
2016-11-03 14:29 ` [RFC PATCH 2/3] rtc: Add Amlogic Virtual Wake RTC Neil Armstrong
2016-11-03 15:36 ` Mark Rutland
2016-11-03 15:46 ` Neil Armstrong [this message]
2016-12-01 0:51 ` [rtc-linux] " Alexandre Belloni
2016-11-03 14:29 ` [RFC PATCH 3/3] ARM64: dts: meson-gxbb: Add support for PM and Virtual RTC Neil Armstrong
2016-11-03 15:25 ` [RFC PATCH 0/3] ARM64: meson-gxbb: Add support for system suspend Mark Rutland
2016-11-03 15:43 ` Mark Rutland
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