Re: [GIT PULL 1/7] soc/tegra: Changes for v5.20-rc1

[Thierry Reding <thierry.reding@gmail.com>]

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On Tue, Jul 12, 2022 at 03:27:16PM +0200, Arnd Bergmann wrote:
> On Fri, Jul 8, 2022 at 8:56 PM Thierry Reding <thierry.reding@gmail.com> wrote:
> >   git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux.git tags/tegra-for-5.20-soc
> ...
> > ----------------------------------------------------------------
> > soc/tegra: Changes for v5.20-rc1
> >
> > The bulk of these changes is the new CBB driver which is used to provide
> > (a lot of) information about SErrors when things go wrong, instead of
> > the kernel just crashing or hanging.
> >
> > In addition more SoC information is exposed to sysfs and various minor
> > issues are fixed.
> >
> 
> Hi Thierry,
> 
> I fear I'm going to skip this for the current merge window. It looks like
> the CBB driver you add here would fit into the existing drivers/edac/
> subsystem, or at the minimum should have been reviewed by the
> corresponding maintainers (added to Cc)  to decide whether it goes
> there or not.
> 
> I had not previously seen this driver, but I'll let them have a look first.

EDAC looks like it's used primarily for memory controllers, which this
is not. But then I also see explicit references to non-memory-controller
references in the infrastructure, so perhaps this does fit in there. The
CBB driver is primarily a means to provide additional information about
runtime errors, so it's not directly a means of discovering the errors
(they would be detected anyway and cause a crash) and I don't think we
have a means of correcting any of these errors.

I'll ask Sumit to work with the EDAC maintainers on this.

> For the other patches, I found two more problems:
> 
> > Bitan Biswas (1):
> >       soc/tegra: fuse: Expose Tegra production status
> 
> Please don't just add random attributes in the soc device infrastructure.
> This one has a completely generic name but a SoC specific
> meaning, and it lacks a description in Documentation/ABI.
> Not sure what the right ABI is here, but this is something that needs
> to be discussed more broadly when you send a new version.

I wasn't aware that the SoC device infrastructure was restricted to only
standardized attributes. Looks like there are a few other outliers that
add custom attributes: UX500, ARM Integrator and RealView, and OMAP2.

Do we have some other place where this kind of thing can be exposed? Or
do we just need to come up with some better way of namespacing these?
Perhaps it would also be sufficient if all of these were better
documented so that people know what to look for on their platform of
interest.

> I see there are already some custom attributes in the same device,
> we should probably not have added those either, but I suppose
> we are stuck with those, so please add the missing documentation.

Yeah, that's a good point. These should definitely be documented
properly.

> 
> > YueHaibing (1):
> >      soc/tegra: fuse: Add missing DMADEVICES dependency
> 
> This one fixes the warning the wrong way: we don't 'select' random
> drivers from other subsystems, and selecting the entire
> subsystem makes it worse. Just drop the 'select' here and
> enable the drivers in the defconfig.

This doesn't actually select the DMADEVICES property. It adds a
dependency on DMADEVICES and if that is met it will select
TEGRA20_APB_DMA.

Thierry

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