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Date:      Wed, 28 Apr 2021 09:01:56 +0100
From:      Mark Murray <markm@FreeBSD.org>
To:        Mark Millard <marklmi@yahoo.com>
Cc:        freebsd-arm <freebsd-arm@freebsd.org>
Subject:   Re: I2C/IIC working on RPI4 8GB?
Message-ID:  <47A634E3-4938-4AFC-9341-E480CEBF67FB@FreeBSD.org>
In-Reply-To: <C4828BF2-E8B7-45D1-B0F8-5E72AF84D565@yahoo.com>
References:  <1C2DD11C-B1F6-4C2A-9AB0-5F1553520FF5@FreeBSD.org> <20210426161138.a8f44b6e1134f73a411be57d@bidouilliste.com> <CF4C4332-BB2F-47E9-B879-8EEA0E53E848@FreeBSD.org> <C4828BF2-E8B7-45D1-B0F8-5E72AF84D565@yahoo.com>

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On 27 Apr 2021, at 21:13, Mark Millard <marklmi@yahoo.com> wrote:
>=20
> Did you try the suggestion in:
>=20
> https://lists.freebsd.org/pipermail/freebsd-arm/2021-April/023687.html
>=20
> ? It suggests that you need to have the config.txt swap
> the the pins in order to undo another swap that happens
> at some internal stage. The swapped problem was indicated
> to be visible in the dmesg reporting and the manual swap
> was reported to cause the dmesg reporting to produce the
> correct overall result.

I took apart the i2c1.dtbo overlay that mentions pins 2, 3, and swapped =
them, and reassembled the overlay.

Nope. Same problem.

What I have:

[root@grasshopper ~]# dmesg | egrep -i 'ds3231|rtc|i2c|iic|time-of-day'
iichb0: <BCM2708/2835 BSC controller> mem 0x7e804000-0x7e804fff irq 26 =
on simplebus0
iicbus0: <OFW I2C bus> on iichb0
iic0: <I2C generic I/O> on iicbus0
Warning: no time-of-day clock registered, system time will not be set =
accurately

[root@grasshopper ~]# ls -al /dev | grep iic
crw-------   1 root  wheel     0x44 Apr 28 08:42 iic0

I have found a PDF document "BCM2711 ARM Peripherals", and it says "The =
BSC controller in the BCM2711 fixes the clock-strectching[sic] bug that =
was present in BCM283x devices", so I suspect that the device may not be =
hardware compatible with the RPI3 and earlier.

Time to dig in and hack.

M
--
Mark R V Murray


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