From: Neil Armstrong <narmstrong@baylibre.com>
To: tanure@linux.com, linux-amlogic@lists.infradead.org
Subject: Re: VIM3 - A311D - I2C AO Clock Questions
Date: Mon, 7 Mar 2022 09:29:15 +0100 [thread overview]
Message-ID: <35db71b9-6574-b517-9687-33a826647821@baylibre.com> (raw)
In-Reply-To: <CAJX_Q+0Gvf88EW6s6-pLoA_mwhwKCf==qyxmNnFt=S24TPN0xw@mail.gmail.com>
Hi,
On 06/03/2022 11:23, Lucas Tanure wrote:
> Hi,
>
> I am trying to integrate an I2C device into VIM3 using the I2C_AO bus.
> My device uses a 100000Hz clock, but after changing
> meson-g12b-a311d-khadas-vim3.dts to add my I2C node the driver could
> not properly read its registers.
>
> It reads 0x9100, but the correct data should be 0xcb58.
> The first thing I saw on the bus was that the frequency I requested by
> the device tree was being set after the probe of my driver already
> failed.
> For that, I sent "i2c: meson: Fix wrong speed use from probe" which
> fixes that issue.
>
> But I still get the wrong data, so my next guess is that the clock
> duty cycle is 30%, and I think should be 50%.
> Here is an image of the signals of the bus:
> https://pasteboard.co/TEoxQucsXUUD.png
>
> I have tested other frequencies and all of them uses a 30% duty cycle,
> where SCL is up 30% and low for 70% of the period.
Indeed it seems by default the duty cycle is for Fast Mode, but standard mode should
be around 50%. Did you try 400khz ?
Amlogic did some changes on their off-tree linux fork, please look around:
https://github.com/khadas/linux/blob/khadas-vims-5.4.y-fc/drivers/i2c/busses/i2c-meson.c#L143
I'm unsure when REG_SLAVE_ADDR BIT(28) appeared, but if you try to port this upstream,
we'll be happy to review it for inclusion.
Neil
>
> Is possible to configure the clock to be 100000Hz, but with a 50% duty
> cycle for this I2C bus on A3111D?
>
> Thanks
> Lucas Tanure
>
> _______________________________________________
> linux-amlogic mailing list
> linux-amlogic@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-amlogic
_______________________________________________
linux-amlogic mailing list
linux-amlogic@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-amlogic
next prev parent reply other threads:[~2022-03-07 8:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAJX_Q+2zibb_ABAjT=k=hbW_Xa9knOy5hcN5Ma2B6Z+h-3=FsQ@mail.gmail.com>
2022-03-06 10:23 ` Lucas Tanure
2022-03-07 8:29 ` Neil Armstrong [this message]
2022-03-08 6:49 ` Lucas Tanure
2022-03-09 9:39 ` Lucas Tanure
2022-03-21 10:08 ` Lucas Tanure
2022-03-25 12:22 ` Jian Hu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=35db71b9-6574-b517-9687-33a826647821@baylibre.com \
--to=narmstrong@baylibre.com \
--cc=linux-amlogic@lists.infradead.org \
--cc=tanure@linux.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®