From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko =?ISO-8859-1?Q?St=FCbner?= Subject: Re: [PATCH] arm64: dts: rockchip: add i2c nodes for rk3399 Date: Sat, 18 Jun 2016 14:01:08 +0200 Message-ID: <1633653.D0508meTWe@diego> References: <1463429371-10950-1-git-send-email-dianders@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <1463429371-10950-1-git-send-email-dianders@chromium.org> Sender: linux-kernel-owner@vger.kernel.org To: Douglas Anderson Cc: linux-rockchip@lists.infradead.org, david.wu@rock-chips.com, jay.xu@rock-chips.com, briannorris@chromium.org, wsa@the-dreams.de, linux-i2c@vger.kernel.org, robh+dt@kernel.org, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, catalin.marinas@arm.com, will.deacon@arm.com, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org List-Id: devicetree@vger.kernel.org Am Montag, 16. Mai 2016, 13:09:31 schrieb Douglas Anderson: > From: David Wu > > We've got 9 (count em!) i2c controllers on rk3399, some of which are in > the PMU power domain and some of which are normal peripherals. Add them > all to the main rk3399 dtsi file so future patches can turn them on in > the board dts files. > > Note: by default we try to set the i2c clock rate to 200 MHz so that we > can achieve good i2c functional clock rates. 200 MHz gives us the > ability to make very close to 100 kHz / 400 kHz / 1 MHz rates. If > boards want to tune clock rates further they can always override. > Possibly boards could want to tune this if: > - they wanted to save an infinitesimal amount of power and they knew > their i2c bus was slow anyway. Since we gate the functional clock > when the i2c bus is not active, power savings would only be while i2c > transfers were happening and probably won't be very big anyway. > - they wanted to eek out a bit more speed by carefully tuning the source > clock to make divisions work out perfectly, accounting for the rise / > fall time measured on an actual board. > > Note also that we still request 200 MHz for the PMU i2c busses even > though we expect that we won't make that exactly (currently PPLL is 676 > MHz which gives us 169 MHz). > > Signed-off-by: David Wu > Signed-off-by: Jianqun Xu > [dianders: wrote desc; put in assigned-clocks; reordered nodes] > Signed-off-by: Douglas Anderson applied to my dts64 branch for 4.8 Thanks Heiko