From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Subject: Re: [PATCH 1/2] I2C: Set I2C timing registers for mxs-i2c Date: Mon, 30 Apr 2012 22:47:17 +0200 Message-ID: <201204302247.17242.marex@denx.de> References: <1335738969-27445-1-git-send-email-marex@denx.de> <201204302209.12482.marex@denx.de> <20120430202742.GC28226@pengutronix.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120430202742.GC28226-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Linux I2C , Detlev Zundel , Fabio Estevam , Stefano Babic , Wolfgang Denk List-Id: linux-i2c@vger.kernel.org Dear Wolfram Sang, > > > > > > This sets the bus to run at 400kHz, prior to this, > > > > > > the bus frequency was undefined. > > > > > > > > > > Not exactly. The default values let it run at 100kHz. > > > > > > > > Have you tried dumping the default values and comparing it with the > > > > values for 100kHz in the manual? > > > > > > Yes, sure. Doesn't it work for you? I just rechecked and the values are > > > okay. That being said, if you make it configurable for 400kHz, it would > > > in deed be better to rewrite the values for 100kHz, too. > > > > They were different for me ... did you configure the i2c bus in your > > bootloader possibly? Those values might have been written there since > > then ... I didn't run i2c in u-boot before booting linux. > > Nope, no I2C involved in the bootloader at all. Do you get the correct > values after soft-resetting the device? > > It doesn't really matter, though. Just reinit them to the proper values > depending on the user setting. Indeed. Default to 100kHz might be a good idea too, in case user entered some weird value. Eventually, it'd be nice if we could calculate the timing values for all possible frequencies, but I didn't got to deriving such formula ... dunno if it's worth it either, doubt so. Best regards, Marek Vasut