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From: "Svenning Sørensen" <sss-sijd2F9aCfdBDgjK7y7TUQ@public.gmane.org>
To: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] i2c: scx200_acb: avoid I2C bus overclocking.
Date: Tue, 12 May 2015 23:09:53 +0200	[thread overview]
Message-ID: <55526C21.5070801@secomea.com> (raw)
In-Reply-To: <20150512201919.GL4449-oo5tB6JMkjKRinMKxDlMNPwbnWRJjS81@public.gmane.org>

On 12-05-2015 22:19, Wolfram Sang wrote:
> On Thu, Apr 23, 2015 at 10:27:50PM +0200, Svenning Sørensen wrote:
>> According to I2C spec, max SCL rate is 100 kHz, but SCx200/CS5536
>> controller is currently driving it at 214 kHz according to my math.
>>
>> SCL is derived from an input clock of 48 MHz, which must be divided
>> by 480 (240 cycles for each SCL high/low state) to be within spec.
>>
>> Signed-off-by: Svenning Soerensen <sss-sijd2F9aCfdBDgjK7y7TUQ@public.gmane.org>
> 
> So, did you test/measure the actual frequency? Or is this patch based on
> specs only? Thanks for caring about this old driver, though!
> 

Unfortunately I don't have any scope, so it is based on datasheet only.

I noticed sporadic i2c errors reading the temperature on some of my
PC Engines Alix.2 boards (with LM86 sensor chip) so started digging
the datasheets and driver for an explanation.

I haven't noticed any problems after this change.

  parent reply	other threads:[~2015-05-12 21:09 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-23 20:27 [PATCH] i2c: scx200_acb: avoid I2C bus overclocking Svenning Sørensen
     [not found] ` <553955C6.3030000-sijd2F9aCfdBDgjK7y7TUQ@public.gmane.org>
2015-05-12 20:19   ` Wolfram Sang
     [not found]     ` <20150512201919.GL4449-oo5tB6JMkjKRinMKxDlMNPwbnWRJjS81@public.gmane.org>
2015-05-12 21:09       ` Svenning Sørensen [this message]
2015-06-02 18:21   ` Wolfram Sang
2015-10-25 15:47     ` Wolfram Sang

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