Hi Scott,

Please see my replay inline.

-----Original Message-----
From: linux-arm-kernel <redacted>
On Behalf Of Scott Wood
Sent: 2018?9?4? 4:34
To: Andy Tang <redacted>; Vabhav Sharma
[off-list ref]; linux-kernel at vger.kernel.org;
devicetree at vger.kernel.org; robh+dt at kernel.org;
mark.rutland at arm.com; linuxppc-dev at lists.ozlabs.org;
linux-arm-kernel at lists.infradead.org; mturquette at baylibre.com;
sboyd at kernel.org; rjw at rjwysocki.net; viresh.kumar at linaro.org;
linux-clk at vger.kernel.org; linux-pm at vger.kernel.org;
linux-kernel-owner at vger.kernel.org; catalin.marinas at arm.com;
will.deacon at arm.com; gregkh at linuxfoundation.org; arnd at arndb.de;
kstewart at linuxfoundation.org; yamada.masahiro at socionext.com
Cc: Yogesh Narayan Gaur <redacted>;
linux at armlinux.org.uk; Varun Sethi [off-list ref]; Udit Kumar
[off-list ref]
Subject: Re: [PATCH 3/5] drivers: clk-qoriq: Add clockgen support for
lx2160a

On Mon, 2018-09-03 at 01:17 +0000, Andy Tang wrote:

quoted

Hi Scott,

Please see my replay in line.

quoted

-----Original Message-----
From: Linuxppc-dev
[off-list ref] On
Behalf Of Scott Wood
Sent: 2018?9?1? 4:29
To: Andy Tang <redacted>; Vabhav Sharma
[off-list ref]; linux-kernel at vger.kernel.org;
devicetree at vger.kernel.org; robh+dt at kernel.org;
mark.rutland at arm.com; linuxppc-dev at lists.ozlabs.org;
linux-arm-kernel at lists.infradead.org; mturquette at baylibre.com;
sboyd at kernel.org; rjw at rjwysocki.net; viresh.kumar at linaro.org;
linux-clk at vger.kernel.org; linux-pm at vger.kernel.org;
linux-kernel-owner at vger.kernel.org; catalin.marinas at arm.com;
will.deacon at arm.com; gregkh at linuxfoundation.org; arnd at arndb.de;
kstewart at linuxfoundation.org; yamada.masahiro at socionext.com
Cc: Yogesh Narayan Gaur <redacted>;
linux at armlinux.org.uk; Udit Kumar [off-list ref]; Varun

Sethi

quoted

quoted

[off-list ref]
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:

quoted

We don't want to increase NUM_CMUX each time new soc with

more

quoted

quoted

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.

quoted

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"?

[Andy] Sorry, "Often" is not a right word. I meant we tend to add new soc without updating NUM_CMUX.
 

quoted

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).

[Andy] I don't see any impropriate about your suggestion. so we are going to do in your way.

Thanks,
Andy

-Scott



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