From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH] i2c: busses: i2c-bcm2835: S-Register clear reserved bits Date: Tue, 16 Jun 2015 19:34:36 -0600 Message-ID: <5580CEAC.6070109@wwwdotorg.org> References: <1434469259-6474-1-git-send-email-linux_wi@tinag.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1434469259-6474-1-git-send-email-linux_wi-ADq4ffItWIY@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Silvan Wicki , wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-i2c@vger.kernel.org On 06/16/2015 09:40 AM, Silvan Wicki wrote: > The Datasheet mentions on page 31 that the bits 10-31 must be read as > don't care and written as 0. > https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf > > We cannot guarantee that we reed bits 10-31 as always 0 (becuase the > datasheet says read as don't care). We clear the bits with a bitmask to > prevent writing back unknown data at the reserved bits. I guess that's true. Acked-by: Stephen Warren