On Mon, 2018-09-03 at 01:17 +0000, Andy Tang wrote: > Hi Scott, > > Please see my replay in line. > > > -----Original Message----- > > From: Linuxppc-dev > > <linuxppc-dev-bounces+b29983=freescale.com@xxxxxxxxxxxxxxxx> On > > Behalf Of Scott Wood > > Sent: 2018年9月1日 4:29 > > To: Andy Tang <andy.tang@xxxxxxx>; Vabhav Sharma > > <vabhav.sharma@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; > > devicetree@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; > > mark.rutland@xxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx; > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; mturquette@xxxxxxxxxxxx; > > sboyd@xxxxxxxxxx; rjw@xxxxxxxxxxxxx; viresh.kumar@xxxxxxxxxx; > > linux-clk@xxxxxxxxxxxxxxx; linux-pm@xxxxxxxxxxxxxxx; > > linux-kernel-owner@xxxxxxxxxxxxxxx; catalin.marinas@xxxxxxx; > > will.deacon@xxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; arnd@xxxxxxxx; > > kstewart@xxxxxxxxxxxxxxxxxxx; yamada.masahiro@xxxxxxxxxxxxx > > Cc: Yogesh Narayan Gaur <yogeshnarayan.gaur@xxxxxxx>; > > linux@xxxxxxxxxxxxxxx; Udit Kumar <udit.kumar@xxxxxxx>; Varun Sethi > > <V.Sethi@xxxxxxx> > > Subject: Re: [PATCH 3/5] drivers: clk-qoriq: Add clockgen support for > > lx2160a > > > > On Fri, 2018-08-31 at 06:12 +0000, Andy Tang wrote: > > > We don't want to increase NUM_CMUX each time new soc with more > > > > cmuxes added. > > > > You don't want to have to make a trivial change each time you exceed a > > limit that has yet to be exceeded once since NUM_CMUX was added? > > This isn't ABI or in any other way hard to change. It's right in the same > > file > > as the chip description you'd be adding. > > > > And even if a chip did come along with 16 cmuxes, you'd then need to > > increase the array to 17 to hold the -1 if you don't want to leave a > > situation > > like the > > p4080 is in now, where a chip's cmux array could be broken by increasing > > NUM_CMUX further. > > > > [Andy] Adding buffer to a limitation number is always a good habit when > coding. We often forget to increase this value when > a new chip with more cmuxes added. "often"? There has never been a new chip added with more cmuxes than p4080's 8, and if one does come along and you forget, the compiler should complain about exceeding the array length with a static initializer. This isn't like an array that is filled with a runtime-determined length. > Like this patch, we didn't increase this value at first. We spent a lot of > time finding out that NUM_CMUX needs to be increased too. Are you talking about some other chip that you haven't sent a patch for yet? Or is the cmux array for this chip wrong? What specifically did you see happen "at first"? > It is a personal preference how to set this value. I think it is better to > increase it to 16, not NUM_CMUX+1 as long as we fix the P4080 issue > even though it is a trivial change. And I agree the description needs to be > updated. I'm not the clock maintainer, so it's not up to me, but I don't see the point in setting it to an arbitrary number, and I do not agree that increasing NUM_CMUX is a suitable replacement for NUM_CMUX+1 in cmux_to_group[], as that array should be one larger than cmux[] in order to allow every chip to have a -1 terminator. In any case, any change to NUM_CMUX should be a separate patch because it's not required for lx2160a support (assuming lx2160a was correctly described by this patch). -Scott
