linux-kernel - Re: [PATCH v9 0/3] Tango PCIe controller support

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Message-ID: <20170705213419.GD25063@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 5 Jul 2017 16:34:19 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Mason <slash.tmp@...e.fr>
Cc:     Marc Gonzalez <marc_gonzalez@...madesigns.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        DT <devicetree@...r.kernel.org>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>
Subject: Re: [PATCH v9 0/3] Tango PCIe controller support

On Wed, Jul 05, 2017 at 10:39:19PM +0200, Mason wrote:
> On 05/07/2017 20:03, Bjorn Helgaas wrote:
> 
> > On Wed, Jul 05, 2017 at 12:55:37AM +0200, Mason wrote:
> >
> >> On 04/07/2017 22:24, Bjorn Helgaas wrote:
> >>
> >>> I made the trivial changes I mentioned, added a dependency on
> >>> CONFIG_BROKEN (for the config/MMIO muxing issue), and put these on
> >>> pci/host-tango.  I can't build or test this, so I probably broke
> >>> something in the process.  I think the combination of the boot-time
> >>> warning, the taint, and CONFIG_BROKEN is a reasonable amount of
> >>> warning that a user should expect issues.
> >>>
> >>> Can you take a look and see if it works for you?
> >>>
> >>> https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=pci/host-tango
> >>
> >> Thanks. I'll take it for a spin ASAP.
> >>
> >> TAINT_CRAP... Smirk. I didn't see that one in the docs:
> >> https://www.kernel.org/doc/html/latest/admin-guide/tainted-kernels.html
> >>
> >> Oh wait... TAINT_CRAP is "C" => a staging driver has been loaded
> > 
> > I wish it had a less pejorative, more descriptive name.  But it seems like
> > the closest to this situation.
> 
> Maybe it is not too late to submit a patch to Linus
> renaming TAINT_CRAP?
> 
> Here are a few candidates, off the top of my head:
> 
> TAINT_STAGING
> TAINT_STAGING_DRIVER
> TAINT_BROKEN_HW
> TAINT_BROKEN_HARDWARE
> TAINT_USE_AT_YOUR_OWN_RISK

I personally wouldn't object, but it's not a PCI thing so that can all
be separate from this driver.

> >> The one issue I anticipate with "depends on BROKEN" is
> >> when I add support for revision 2, which isn't broken.
> > 
> > How about this:
> > 
> >   - Rename PCIE_TANGO to PCIE_TANGO_REV1
> >   - PCIE_TANGO_REV1 depends on BROKEN
> >   - Add rev2 support later, enabled by PCIE_TANGO
> >   - PCIE_TANGO_REV1 depends on PCIE_TANGO && BROKEN
> > 
> > I updated pci/host-tango along these lines (without rev2 support,
> > obviously).
> 
> And support for REV1 wouldn't be compiled in, unless
> BROKEN is selected? Yes, I think that could fly.

Right.

> Don't you think the naming should follow the DT
> convention of using the first SoC embedding the
> IP (for the compatible string) ?
> 
> PCIE_TANGO_REV1 vs PCIE_TANGO_SMP8759

Sounds reasonable.  So v2 will be something other than SMP8759?
I renamed it to CONFIG_PCIE_TANGO_SMP8759.

> > I forgot to ask for a MAINTAINERS update.  Can you send that, too,
> > please?
> 
> There's a "catch-all" rule for everything tango-related:
> 
> ARM/TANGO ARCHITECTURE
> M:	Marc Gonzalez <marc_gonzalez@...madesigns.com>
> L:	linux-arm-kernel@...ts.infradead.org
> S:	Maintained
> N:	tango
> 
> Is that enough?

Yep, sorry I didn't notice that.  That's enough for
scripts/get_maintainer.pl to work, which is what I'm looking for.

If you confirm that
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/host-tango&id=d752a8b29345
works for you, I'll include it in my v4.13 pull request.

Bjorn