From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?U3Zlbm5pbmcgU8O4cmVuc2Vu?= Subject: Re: [PATCH] i2c: scx200_acb: avoid I2C bus overclocking. Date: Tue, 12 May 2015 23:09:53 +0200 Message-ID: <55526C21.5070801@secomea.com> References: <553955C6.3030000@secomea.com> <20150512201919.GL4449@schokonusskuchen.bad> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20150512201919.GL4449-oo5tB6JMkjKRinMKxDlMNPwbnWRJjS81@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org On 12-05-2015 22:19, Wolfram Sang wrote: > On Thu, Apr 23, 2015 at 10:27:50PM +0200, Svenning S=C3=B8rensen wrot= e: >> 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 >=20 > So, did you test/measure the actual frequency? Or is this patch based= on > specs only? Thanks for caring about this old driver, though! >=20 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.