From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: [PATCH v3 5/5] powerpc/85xx: i2c-mpc: use new I2C bindings for the Socates board Date: Wed, 08 Apr 2009 20:27:12 +0200 Message-ID: <49DCEC80.2050507@grandegger.com> References: <20090407082052.477328750@denx.de> <20090407082231.803193635@denx.de> <49DC4F4D.10803@grandegger.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-mnsaURCQ41sdnm+yROfE0A@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-mnsaURCQ41sdnm+yROfE0A@public.gmane.org To: Grant Likely Cc: linuxppc-dev-mnsaURCQ41sdnm+yROfE0A@public.gmane.org, devicetree-discuss-mnsaURCQ41sdnm+yROfE0A@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ben Dooks List-Id: linux-i2c@vger.kernel.org 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. Wolfgang. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <49DCEC80.2050507@grandegger.com> Date: Wed, 08 Apr 2009 20:27:12 +0200 From: Wolfgang Grandegger MIME-Version: 1.0 To: Grant Likely Subject: Re: [PATCH v3 5/5] powerpc/85xx: i2c-mpc: use new I2C bindings for the Socates board References: <20090407082052.477328750@denx.de> <20090407082231.803193635@denx.de> <49DC4F4D.10803@grandegger.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Cc: linuxppc-dev@ozlabs.org, devicetree-discuss@ozlabs.org, linux-i2c@vger.kernel.org, Ben Dooks List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. Wolfgang.