From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from na01-bn1-obe.outbound.protection.outlook.com (mail-bn1on0113.outbound.protection.outlook.com [157.56.110.113]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 164291A0035 for ; Fri, 7 Nov 2014 08:58:32 +1100 (AEDT) Message-ID: <1415311098.23458.405.camel@snotra.buserror.net> Subject: Re: [PATCH] i2c-qoriq: modified compatibility for correct prescaler From: Scott Wood To: Valentin Longchamp Date: Thu, 6 Nov 2014 15:58:18 -0600 In-Reply-To: <5450AC85.40302@keymile.com> References: <1413538026-15739-1-git-send-email-valentin.longchamp@keymile.com> <1414537731.23458.120.camel@snotra.buserror.net> <5450AC85.40302@keymile.com> Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Cc: "Boschung, Rainer" , Linux device trees , "Brunck, Holger" , Linux PowerPC Kernel , Linux I2C List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2014-10-29 at 09:59 +0100, Valentin Longchamp wrote: > On 10/29/2014 12:08 AM, Scott Wood wrote: > > On Fri, 2014-10-17 at 11:27 +0200, Valentin Longchamp wrote: > >> With "fsl-i2c" compatibility the i2c frequency is not set > >> correctly, because it sets no prescaler. According to the AN2919 from > >> Freescale and the QorIQ (P2041) documentation, the source clock is 1/2 > >> the platform clock. This implies that a prescaler of 2 must be used. > >> > >> This changes the compatibility of the qoriq-i2c .dtsi files to pick the > >> mpc8543, which uses the same driver but sets the correct prescaler. > >> > >> Signed-off-by: Rainer Boschung > >> Signed-off-by: Valentin Longchamp > >> --- > >> > >> arch/powerpc/boot/dts/fsl/qoriq-i2c-0.dtsi | 4 ++-- > >> arch/powerpc/boot/dts/fsl/qoriq-i2c-1.dtsi | 4 ++-- > >> 2 files changed, 4 insertions(+), 4 deletions(-) > >> > >> diff --git a/arch/powerpc/boot/dts/fsl/qoriq-i2c-0.dtsi b/arch/powerpc/boot/dts/fsl/qoriq-i2c-0.dtsi > >> index 5f9bf7d..aa6c366 100644 > >> --- a/arch/powerpc/boot/dts/fsl/qoriq-i2c-0.dtsi > >> +++ b/arch/powerpc/boot/dts/fsl/qoriq-i2c-0.dtsi > >> @@ -36,7 +36,7 @@ i2c@118000 { > >> #address-cells = <1>; > >> #size-cells = <0>; > >> cell-index = <0>; > >> - compatible = "fsl-i2c"; > >> + compatible = "fsl,mpc8543-i2c", "fsl-i2c"; > >> reg = <0x118000 0x100>; > >> interrupts = <38 2 0 0>; > >> dfsrr; > >> @@ -46,7 +46,7 @@ i2c@118100 { > >> #address-cells = <1>; > >> #size-cells = <0>; > >> cell-index = <1>; > >> - compatible = "fsl-i2c"; > >> + compatible = "fsl,mpc8543-i2c", "fsl-i2c"; > >> reg = <0x118100 0x100>; > >> interrupts = <38 2 0 0>; > >> dfsrr; > > > > Are all chips that use this dtsi 100% compatible with mpc8543's i2c, or > > just in ways the Linux driver cares about? > > I have just looked briefly at the mpc8548 RM (covers mpc8543) and its i2c > controller looks the same as the qoriq's. I cannot however state if they are > 100% compatible. > > If we wanted to be on the safe side and strict (since we are not sure that the > hardware is 100% compatible), we maybe should add a fsl,qoriq-i2c compatible to > the driver that does the same as mpc8543-i2c. If we're going to change the device tree I'd rather just add a property to say what the prescaler is. -Scott