Re: [PATCH v3 RESEND] clk: sifive: Fix W=1 kernel build warning

[Lee Jones <lee.jones@linaro.org>]

On Thu, 13 Jan 2022, Lee Jones wrote:

> On Thu, 13 Jan 2022, Zong Li wrote:
> 
> > On Wed, Jan 12, 2022 at 5:09 PM Lee Jones <lee.jones@linaro.org> wrote:
> > >
> > > On Wed, 12 Jan 2022, Zong Li wrote:
> > >
> > > > On Tue, Jan 11, 2022 at 5:32 PM Lee Jones <lee.jones@linaro.org> wrote:
> > > > >
> > > > > On Tue, 11 Jan 2022, Zong Li wrote:
> > > > >
> > > > > > On Mon, Jan 10, 2022 at 5:50 PM Lee Jones <lee.jones@linaro.org> wrote:
> > > > > > >
> > > > > > > Please improve the subject line.
> > > > > > >
> > > > > > > If this is a straight revert, the subject line should reflect that.
> > > > > > >
> > > > > > > If not, you need to give us specific information regarding the purpose
> > > > > > > of this patch.  Please read the Git log for better, more forthcoming
> > > > > > > examples.
> > > > > > >
> > > > > >
> > > > > > It seems to me that this patch is not a straight revert, it provides
> > > > > > another way to fix the original build warnings, just like
> > > > > > '487dc7bb6a0c' tried to do. I guess the commit message has described
> > > > > > what the original warnings is and what the root cause is, it also
> > > > > > mentioned what is changed in this patch. I'm a bit confused whether we
> > > > > > need to add fixes tag, it looks like that it might cause some
> > > > > > misunderstanding?
> > > > >
> > > > > I think it's the patch description and subject that is causing the
> > > > > misunderstanding.
> > > > >
> > > >
> > > > Yes, the subject should be made better.
> > > >
> > > > > Please help me with a couple of points and I'll help you draft
> > > > > something up.
> > > > >
> > > > > Firstly, what alerted you to the problem you're attempting to solve?
> > > > >
> > > >
> > > > I recently noticed the code was changed, I guess that I was missing
> > > > something there. After tracking the log, I found that there is a build
> > > > warning in the original implementation, and it was already fixed, but
> > > > it seems to me that there are still some situations there, please help
> > > > me to see the following illustration.
> > > >
> > > > > > > > --- a/drivers/clk/sifive/fu540-prci.c
> > > > > > > > +++ b/drivers/clk/sifive/fu540-prci.c
> > > > > > > > @@ -20,7 +20,6 @@
> > > > > > > >
> > > > > > > >  #include <dt-bindings/clock/sifive-fu540-prci.h>
> > > > > > > >
> > > > > > > > -#include "fu540-prci.h"
> > > > >
> > > > > How is this related to the issue/patch?
> > > > >
> > > >
> > > > Let's go back to the version without '487dc7bb6a0c' fix. The
> > > > prci_clk_fu540 variable is defined in sifive-fu540-prci.h header,
> > > > however, fu540-prci.c includes this header but doesn't use this
> > > > variable, so the warnings happen.
> > > >
> > > > The easiest way to do it is just removing this line, then the warning
> > > > could be fixed. But as the '487dc7bb6a0c' or this patch does, the code
> > > > should be improved, the prci_clk_fu540 variable shouldn't be defined
> > > > in the header, it should be moved somewhere.
> > > >
> > > > > > > > +struct prci_clk_desc prci_clk_fu540 = {
> > > > > > > > +     .clks = __prci_init_clocks_fu540,
> > > > > > > > +     .num_clks = ARRAY_SIZE(__prci_init_clocks_fu540),
> > > > > > > > +};
> > > > >
> > > > > > > > diff --git a/drivers/clk/sifive/fu540-prci.h b/drivers/clk/sifive/fu540-prci.h
> > > > > > > > index c220677dc010..931d6cad8c1c 100644
> > > > > > > > --- a/drivers/clk/sifive/fu540-prci.h
> > > > > > > > +++ b/drivers/clk/sifive/fu540-prci.h
> > > > > > > > @@ -7,10 +7,6 @@
> > > > > > > > +extern struct prci_clk_desc prci_clk_fu540;
> > > > >
> > > > > > > > diff --git a/drivers/clk/sifive/sifive-prci.c b/drivers/clk/sifive/sifive-prci.c
> > > > > > > > index 80a288c59e56..916d2fc28b9c 100644
> > > > > > > > --- a/drivers/clk/sifive/sifive-prci.c
> > > > > > > > +++ b/drivers/clk/sifive/sifive-prci.c
> > > > > > > > @@ -12,11 +12,6 @@
> > > > > > > >  #include "fu540-prci.h"
> > > > > > > >  #include "fu740-prci.h"
> > > > > > > >
> > > > > > > > -static const struct prci_clk_desc prci_clk_fu540 = {
> > > > > > > > -     .clks = __prci_init_clocks_fu540,
> > > > > > > > -     .num_clks = ARRAY_SIZE(__prci_init_clocks_fu540),
> > > > > > > > -};
> > > > > > > > -
> > > > >
> > > > > I'm not sure if it's you or I that is missing the point here, but
> > > > > prci_clk_fu540 is used within *this* file itself:
> > > > >
> > > >
> > > > Here is another situation I mentioned at the beginning, if we'd like
> > > > to put prci_clk_fu540 here, prci_clk_fu740 should be put here as well.
> > > > I guess you didn't do that because there is a bug in the original
> > > > code, fu740-prci.c misused the fu540-prci.h, so there is no build
> > > > warning on fu740. FU740 still works correctly by misusing the
> > > > fu540-prci.h header because fu740-prci.c doesn't actually use the
> > > > prci_clk_fu740 variable, like fu540 we talked about earlier.
> > > >
> > > > >  static const struct of_device_id sifive_prci_of_match[] = {
> > > > >          {.compatible = "sifive,fu540-c000-prci", .data = &prci_clk_fu540},
> > > > >          {.compatible = "sifive,fu740-c000-prci", .data = &prci_clk_fu740},
> > > > >          {}
> > > > >  };
> > > > >
> > > > > So why are you moving it out to somewhere it is *not* used and making
> > > > > it an extern?  This sounds like the opposite to what you'd want?
> > > >
> > > > The idea is that sifive-prci.c is the core and common part of PRCI,
> > > > and I'd like to separate the SoCs-dependent part into SoCs-dependent
> > > > files, such as fu540-prci.c and fu740-prci.c. The goal is if we add
> > > > new SoCs in the future, we can just put the SoCs-dependent data
> > > > structure in the new C file, and do as minimum modification as
> > > > possible in the core file (i.e. sifive-prci.c). It might also help us
> > > > to see all SoCs-dependent data in one file, then we don't need to
> > > > cross many files. Putting these two variables in sifive-pric.c is the
> > > > right thing to do, but that is why I separate them and make them
> > > > extern in this patch.
> > >
> > > I can see what you are doing, but I don't think this is the right
> > > thing to do.  Please put the struct in the same location as it's
> > > referenced.
> > 
> > If we decide to move them into sifive-prci.c (i.e. put it in where
> > it's referenced.), I worried that we might need to move all stuff
> > which are in fu540-prci.c and fu740-prci.c. Because 'prci_clk_fu540'
> > is referenced in sifive-prci.c, whereas '__prci_init_clocks_fu540' is
> > used by 'prci_clk_fu540', and the almost things in fu540-prci.c are
> > used by '__prci_init_clocks_fu540'. It seems to be a little bit
> > difficult to clearly decouple it for modularization which I want to
> > do. What this patch does might be a accepted way, I hope that you can
> > consider it again.
> > 
> > >
> > > And yes that should also be the case for prci_clk_fu740 and yes, it
> > > was over-looked because it wasn't causing warnings at build time for
> > > whatever reason.
> > >
> > > IMHO, placing 'struct of_device_id' match tables in headers is also
> > > odd and is likely the real cause of this strange situation.
> > 
> > I couldn't see what are you pointing, do you mind give more details
> > about it? It seems to me that the match table is put in C file (i.e.
> > sifive-prci.c).
> 
> Oh, sorry, it's a common source file, rather than a header.
> 
> Okay, so I went and actually looked at the code this time.
> 
> If I were you I would move all of the device specific structs and
> tables into the device specific header files, then delete the device
> specific source (C) files entirely.
> 
> There seems to be no good reason for carrying a common source file as
> well as a source file AND header file for each supported device.
> IMHO, that's over-complicating things for no apparent gain.

I can even do it for you, if you'd like!

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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