[PATCH v7 00/22] RISC-V Kendryte K210 support improvements

[Geert Uytterhoeven]

Hi Damien,

On Thu, Dec 10, 2020 at 1:36 PM Damien Le Moal <Damien.LeMoal at wdc.com> wrote:
> On Thu, 2020-12-10 at 11:04 +0100, Geert Uytterhoeven wrote:
> > On Thu, Dec 10, 2020 at 4:41 AM Damien Le Moal <damien.lemoal at wdc.com> wrote:
> > > Changes from v6:
> > > * Annotate struct platform_driver variables with __refdata to avoid
> > >   section mismatch compilation errors
> >
> > Blindly following the advice from kernel test robot <lkp at intel.com> is
> > not always a good idea:
> >
> >     The variable k210_rst_driver references
> >     the function __init set_reset_devices()
> >     If the reference is valid then annotate the
> >     variable with or __refdata (see linux/init.h) or name the variable:
> >
> > If your driver's probe function is annotated with __init, you cannot
> > have a pointer to it in the driver structure, as any binding done after
> > the freeing of initmem will cause a crash.  Adding the __refdata merely
> > suppresses the warning, and won't avoid the crash.
>
> Hmm... I must be misunderstanding something here. free_initmem() is called from
> kernel_init() right before starting the user init process. That is late enough
> that all drivers are already probed and initialized. At least that is what I
> thought, especially considering that none of the k210 drivers can be modules
> and are all builtin. What am I missing here ?

For these specific cases, binding is indeed unlikely to happen after
free_initmem(). In the generic case that is not true.
However, you can still trigger it manually by unbinding and rebinding
the device manually through sysfs.

> So I think I will go with option 2. It is simpler and safer. We can always
> revisit and optimize later. I would prefer this series to land first :)

Right. Correctness first, performance later.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds