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: > > Hi Scott, > > > > Please see my replay inline. > > > > > -----Original Message----- > > > From: linux-arm-kernel > > > <linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx> > > > On Behalf Of Scott Wood > > > Sent: 2018年8月31日 1:43 > > > To: 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>; Andy Tang > > > <andy.tang@xxxxxxx>; linux@xxxxxxxxxxxxxxx; Varun Sethi > > > <V.Sethi@xxxxxxx>; Udit Kumar <udit.kumar@xxxxxxx> > > > Subject: Re: [PATCH 3/5] drivers: clk-qoriq: Add clockgen support > > > for lx2160a > > > > > > On Thu, 2018-08-30 at 12:39 -0500, Scott Wood wrote: > > > > On Thu, 2018-08-30 at 07:36 +0000, Vabhav Sharma wrote: > > > > > > > > > > > > Why are you increasing NUM_CMUX beyond 8 for a chip that > only > > > > > > has > > > > > > 8 entries in cmux_to_group? > > > > > > > > > > Configuration is 16 cores,8 cluster with 2 cores in each cluster > > > > > > > > So? This is about cmuxes, not cores. You're increasing the array > > > > without ever using the new size. > > > > > > Oh, and you also broke p4080 which has 8 cmuxes but no -1 > > > terminator, because the array was of length 8. Probably the array > > > should be changed to NUM_CMUX+1 so every array can be -1 > terminated. > > > > > > > [Andy] How about we add -1 terminator to p4080 and increase > NUM_CMUX to 16? > > Why 16? What does such a change have to do with this chip, which > according to the rest of the patch has 8 cmuxes? [Andy] NUM_CMUX is a limitation number. We better give it an extra buffer, not exactly equal to the limitation. 16 is the limitation number with extra buffer. > > > 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. 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. 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. BR, Andy > -Scott
