From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Subject: Re: [v3, 4/5] powerpc: dts: t4240: add syscon support for DCFG node Date: Tue, 8 Dec 2015 22:33:27 -0600 Message-ID: <1449635607.15946.165.camel@freescale.com> References: <1448594417-22515-1-git-send-email-yangbo.lu@freescale.com> <1448594417-22515-5-git-send-email-yangbo.lu@freescale.com> <1449596781.15946.126.camel@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-bn1bbn0107.outbound.protection.outlook.com ([157.56.111.107]:57184 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751668AbbLIEdk (ORCPT ); Tue, 8 Dec 2015 23:33:40 -0500 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Lu Yangbo-B47093 , "linux-mmc@vger.kernel.org" , "ulf.hansson@linaro.org" Cc: Xie Xiaobo-R63061 , Li Yang-Leo-R58472 On Tue, 2015-12-08 at 22:30 -0600, Lu Yangbo-B47093 wrote: > > -----Original Message----- > > From: Wood Scott-B07421 > > Sent: Wednesday, December 09, 2015 1:46 AM > > To: Lu Yangbo-B47093; linux-mmc@vger.kernel.org; ulf.hansson@linaro= =2Eorg > > Cc: Xie Xiaobo-R63061; Li Yang-Leo-R58472 > > Subject: Re: [v3, 4/5] powerpc: dts: t4240: add syscon support for = DCFG > > node > >=20 > > On Fri, 2015-11-27 at 11:20 +0800, Yangbo Lu wrote: > > > Add syscon support for DCFG node, so that the driver could use sy= scon > > > regmap interface to access the device config module registers. > > > And the CONFIG_MFD_SYSCON should be enabled for this. > > >=20 > > > Signed-off-by: Yangbo Lu > > > --- > > > Changes for v2: > > > - None > > > Changes for v3: > > > - Added this patch > > > --- > > > arch/powerpc/boot/dts/fsl/t4240si-post.dtsi | 4 +++- > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > >=20 > > > diff --git a/arch/powerpc/boot/dts/fsl/t4240si-post.dtsi > > > b/arch/powerpc/boot/dts/fsl/t4240si-post.dtsi > > > index 68c4ead..5f148b2 100644 > > > --- a/arch/powerpc/boot/dts/fsl/t4240si-post.dtsi > > > +++ b/arch/powerpc/boot/dts/fsl/t4240si-post.dtsi > > > @@ -941,7 +941,9 @@ > > > /include/ "qoriq-mpic4.3.dtsi" > > >=20 > > > guts: global-utilities@e0000 { > > > - compatible =3D "fsl,t4240-device-config", "fsl,qoriq > > > -device > > > -config-2.0"; > > > + compatible =3D "fsl,t4240-device-config", > > > + "fsl,qoriq-device-config-2.0", > > > + "syscon"; > >=20 > >=20 > > I really don't like changing the device tree based on Linux interna= ls. > > It also means that the workaround wouldn't work for users that don'= t > > upgrade their device tree. I definitely don't like one QorIQ chip = having > > "syscon" on the dcfg node but others not having it. > >=20 > > The guts driver should just maintain a list of compatibles to match= =2E Why > > do we need to use syscon, rather than a guts driver that exports an > > fsl_get_svr() function? > >=20 > > -Scott >=20 > [Lu Yangbo-B47093] I think the only difference between fsl_get_svr() = and > syscon is that we don=E2=80=99t need to change dts with fsl_get_svr()= , right? That is one difference. It also would simplify callers, and avoid the = need to depend on the overcomplicated and difficult-to-follow regmap code in or= der to accomplish something very simple. > The syscon has considered the endianess, and we don=E2=80=99t need to= add more code > to use it and only add 'syscon' in the node. Dealing with the endianess in a common guts driver would be trivial. > This patchset only enables syscon in T4240 DFCG node since it has an = erratum > to use it. The device tree describes the hardware, not what you want to use it for= =2E The existence of an erratum in the esdhc block says nothing about what the = dcfg node is. > The fsl_get_svr() you suggested is also an idea for this. > Then, may I know is there a guts driver in kernel? > Thanks a lot.=20 There isn't, but there should be. -Scott