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From: "Diederik de Haas" <diederik@cknow-tech.com>
To: "Diederik de Haas" <diederik@cknow-tech.com>,
	"Heiko Stuebner" <heiko@sntech.de>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>
Cc: "Ricardo Pardini" <ricardo@pardini.net>,
	<devicetree@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-rockchip@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: dts: rockchip: Fix i2c6 clock-frequency on NanoPC-T6
Date: Sat, 12 Sep 2026 17:48:52 +0200	[thread overview]
Message-ID: <DLDGFSSZUIKQ.19CS0SRKYOKOJ@cknow-tech.com> (raw)
In-Reply-To: <DLDEGZ68QQ19.1MJEB7QOK4G7T@cknow-tech.com>

On Sat Sep 12, 2026 at 4:16 PM CEST, Diederik de Haas wrote:
> On Sat Sep 12, 2026 at 2:41 PM CEST, Heiko Stuebner wrote:
>> Am Freitag, 11. September 2026, 17:28:33 Mitteleuropäische Sommerzeit schrieb Diederik de Haas:
>>> The i2c6 bus needs to run at 200kHz, because at the default frequency of
>>> 100kHz it may fail to find the RTC resulting in warnings/errors like
>>> 
>>>   rtc-hym8563 6-0051: no valid clock/calendar values available
>>>   rtc-hym8563 6-0051: hctosys: unable to read the hardware clock
>>> 
>>> But only sometimes. This should not happen when there is a battery backing
>>> the RTC, yet it does ... sometimes.
>>
>> I'm confused, shouldn't a slower clock always work?
>> Like I understand how a clock that is too fast can cause issues due
>> to hardware limitations, but running the bus slower somehow shouldn't
>> cause issues?
>
> Impeccable timing ... as I was just about to retract this patch.
>
> So please ignore/drop this and sorry for the noise.

https://github.com/rockchip-linux/kernel/commit/815c9a084e62d700ab5487974b63035e772a29a4
"remove the buf[0] & HYM8563_SEC_VL, it's unsuitable for some hym8563.
set rtc init time for first power on."

I guess I have 'some hym8563' in both my NanoPC-T6 LTS & Plus :-/
The one in my NanoPi R5S works great, so I'll just use/depend on that one.

WARNING: multiple messages have this Message-ID (diff)
From: "Diederik de Haas" <diederik@cknow-tech.com>
To: "Diederik de Haas" <diederik@cknow-tech.com>,
	"Heiko Stuebner" <heiko@sntech.de>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>
Cc: "Ricardo Pardini" <ricardo@pardini.net>,
	<devicetree@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-rockchip@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: dts: rockchip: Fix i2c6 clock-frequency on NanoPC-T6
Date: Sat, 12 Sep 2026 17:48:52 +0200	[thread overview]
Message-ID: <DLDGFSSZUIKQ.19CS0SRKYOKOJ@cknow-tech.com> (raw)
In-Reply-To: <DLDEGZ68QQ19.1MJEB7QOK4G7T@cknow-tech.com>

On Sat Sep 12, 2026 at 4:16 PM CEST, Diederik de Haas wrote:
> On Sat Sep 12, 2026 at 2:41 PM CEST, Heiko Stuebner wrote:
>> Am Freitag, 11. September 2026, 17:28:33 Mitteleuropäische Sommerzeit schrieb Diederik de Haas:
>>> The i2c6 bus needs to run at 200kHz, because at the default frequency of
>>> 100kHz it may fail to find the RTC resulting in warnings/errors like
>>> 
>>>   rtc-hym8563 6-0051: no valid clock/calendar values available
>>>   rtc-hym8563 6-0051: hctosys: unable to read the hardware clock
>>> 
>>> But only sometimes. This should not happen when there is a battery backing
>>> the RTC, yet it does ... sometimes.
>>
>> I'm confused, shouldn't a slower clock always work?
>> Like I understand how a clock that is too fast can cause issues due
>> to hardware limitations, but running the bus slower somehow shouldn't
>> cause issues?
>
> Impeccable timing ... as I was just about to retract this patch.
>
> So please ignore/drop this and sorry for the noise.

https://github.com/rockchip-linux/kernel/commit/815c9a084e62d700ab5487974b63035e772a29a4
"remove the buf[0] & HYM8563_SEC_VL, it's unsuitable for some hym8563.
set rtc init time for first power on."

I guess I have 'some hym8563' in both my NanoPC-T6 LTS & Plus :-/
The one in my NanoPi R5S works great, so I'll just use/depend on that one.

_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

  reply	other threads:[~2026-09-12 15:48 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-11 15:28 [PATCH] arm64: dts: rockchip: Fix i2c6 clock-frequency on NanoPC-T6 Diederik de Haas
2026-09-11 15:28 ` Diederik de Haas
2026-09-12 12:41 ` Heiko Stuebner
2026-09-12 12:41   ` Heiko Stuebner
2026-09-12 14:16   ` Diederik de Haas
2026-09-12 14:16     ` Diederik de Haas
2026-09-12 15:48     ` Diederik de Haas [this message]
2026-09-12 15:48       ` Diederik de Haas

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