From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kumar Gala Subject: Re: [PATCH v3 5/5] powerpc/85xx: i2c-mpc: use new I2C bindings for the Socates board Date: Wed, 8 Apr 2009 13:43:11 -0500 Message-ID: References: <20090407082052.477328750@denx.de> <20090407082231.803193635@denx.de> <49DC4F4D.10803@grandegger.com> <49DCEC80.2050507@grandegger.com> Mime-Version: 1.0 (Apple Message framework v930.3) Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49DCEC80.2050507-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfgang Grandegger Cc: Grant Likely , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ben Dooks , linuxppc-dev-mnsaURCQ41sdnm+yROfE0A@public.gmane.org, devicetree-discuss-mnsaURCQ41sdnm+yROfE0A@public.gmane.org List-Id: linux-i2c@vger.kernel.org On Apr 8, 2009, at 1:27 PM, Wolfgang Grandegger wrote: > Grant Likely wrote: >> On Wed, Apr 8, 2009 at 12:16 AM, Wolfgang Grandegger > > wrote: >>> Grant Likely wrote: >>>> On Tue, Apr 7, 2009 at 1:20 AM, Wolfgang Grandegger >>> > wrote: >>>>> Preserve I2C clock settings for the Socrates MPC8544 board. >>>> I had thought that the preserve-clocking property was intended for >>>> older boards that don't currently have any method of getting the >>>> clock >>>> setting out of u-boot. Since Socrates is a new board, U-Boot >>>> should >>>> probably be made to fill in the real clock rate setting. >>> I'm not sure if I understand what you mean. If an old version of U- >>> Boot >>> on an old board sets the I2C clock, it can be used (inherited) by >>> Linux >>> using the property "preserve-clocking". >>> >>> It is actually the customers choice to set the I2C clock in U-Boot >>> and >>> re-use it by Linux. >> >> Setting it in the register != recording the value in the device tree. >> I'm saying that since Socrates is a new board it should not use the >> preserve-clocking dirty trick (and it is a dirty trick) because the >> correct clocking data can be passed via the device tree. > > Why should an old board then use it. "fsl, preserve-clocking" is a new > feature, like using "clock-frequency" and you have the choice to > explicitly set the clocking via device tree or inherit it from the > boot > loader. So far, a fixed FDR/DFRSS value (0x1031) was written to the > registers by Linux. I think Grant's point is socrates is a new board with a new u-boot. That u-boot should be able to set the clock-frequency property in i2c. One assumes if you a clock-frequency property you wouldn't use "fsl,preserve-clocking". (However -- its feasible they are mutually exclusive). - k