Re: [Linux-kernel-mentees] [PATCH v1] gpio: ml: ioh: Convert to dev_pm_ops

Re: [Linux-kernel-mentees] [PATCH v1] gpio: ml: ioh: Convert to dev_pm_ops

[Bjorn Helgaas]

[+cc linux-pci]

On Thu, Apr 02, 2020 at 11:23:27PM +0300, Andy Shevchenko wrote:
> On Thu, Apr 2, 2020 at 11:16 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > On Thu, Apr 02, 2020 at 09:33:46PM +0300, Andy Shevchenko wrote:
> > > On Thu, Apr 2, 2020 at 6:52 PM Vaibhav Gupta <vaibhavgupta40@gmail.com> wrote:
> > > >
> > > > Convert the legacy callback .suspend() and .resume()
> > > > to the generic ones.
> > >
> > > Thank you for the patch.
> > >
> > > Rather then doing this I think the best approach is to unify gpio-pch
> > > and gpio-ml-ioh together.
> > > Under umbrella of the task, the clean ups like above are highly
> > > appreciated.
> >
> > I'd be all in favor of that, but what Vaibhav is working toward is
> > eliminating use of legacy PM in PCI drivers.  I think unifying drivers
> > is really out of scope for that project.
> >
> > If you'd rather leave gpio-ml-ioh.c alone for now, I suggest that
> > Vaibhav move on to other PCI drivers that use legacy PM.  If we
> > convert all the others away from legacy PM and gpio-ml-ioh.c is the
> > only one remaining, then I guess we can revisit this :)
> 
> Then skip this driver for good.
> 
> > Or, maybe converting gpio-ml-ioh.c now, along the lines of
> > 226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"), would be one small
> > step towards the eventual unification, by making gpio-pch and
> > gpio-ml-ioh a little more similar.
> 
> I think it will delay the real work here (very old code motivates
> better to get rid of it then semi-fixed one).

With respect, I think it is unreasonable to use the fact that
gpio-ml-ioh and gpio-pch should be unified to hold up the conversion
of gpio-ml-ioh to generic power management.

I do not want to skip gpio-ml-ioh for good, because it is one of the
few remaining drivers that use the legacy PCI PM interfaces.  We are
very close to being able to remove a significant amount of ugly code
from the PCI core.

gpio-ml-ioh and gpio-pch do look quite similar, and no doubt it would
be great to unify them.  But without datasheets or hardware to test,
that's not a trivial task, and I don't think that burden should fall
on anyone who wants to make any improvements to these drivers.

Another alternative would be to remove legacy PCI PM usage
(ioh_gpio_suspend() and ioh_gpio_resume()) from gpio-ml-ioh.  That
would mean gpio-ml-ioh wouldn't support power management at all, which
isn't a good thing, but maybe it would be even more motivation to
unify it with gpio-pch (which has already been converted by
226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"))?

Bjorn

Re: [Linux-kernel-mentees] [PATCH v1] gpio: ml: ioh: Convert to dev_pm_ops

[Andy Shevchenko]

On Thu, Jul 08, 2021 at 04:47:06PM -0500, Bjorn Helgaas wrote:
> On Thu, Apr 02, 2020 at 11:23:27PM +0300, Andy Shevchenko wrote:
> > On Thu, Apr 2, 2020 at 11:16 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > On Thu, Apr 02, 2020 at 09:33:46PM +0300, Andy Shevchenko wrote:
> > > > On Thu, Apr 2, 2020 at 6:52 PM Vaibhav Gupta <vaibhavgupta40@gmail.com> wrote:
> > > > >
> > > > > Convert the legacy callback .suspend() and .resume()
> > > > > to the generic ones.
> > > >
> > > > Thank you for the patch.
> > > >
> > > > Rather then doing this I think the best approach is to unify gpio-pch
> > > > and gpio-ml-ioh together.
> > > > Under umbrella of the task, the clean ups like above are highly
> > > > appreciated.
> > >
> > > I'd be all in favor of that, but what Vaibhav is working toward is
> > > eliminating use of legacy PM in PCI drivers.  I think unifying drivers
> > > is really out of scope for that project.
> > >
> > > If you'd rather leave gpio-ml-ioh.c alone for now, I suggest that
> > > Vaibhav move on to other PCI drivers that use legacy PM.  If we
> > > convert all the others away from legacy PM and gpio-ml-ioh.c is the
> > > only one remaining, then I guess we can revisit this :)
> > 
> > Then skip this driver for good.
> > 
> > > Or, maybe converting gpio-ml-ioh.c now, along the lines of
> > > 226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"), would be one small
> > > step towards the eventual unification, by making gpio-pch and
> > > gpio-ml-ioh a little more similar.
> > 
> > I think it will delay the real work here (very old code motivates
> > better to get rid of it then semi-fixed one).
> 
> With respect, I think it is unreasonable to use the fact that
> gpio-ml-ioh and gpio-pch should be unified to hold up the conversion
> of gpio-ml-ioh to generic power management.
> 
> I do not want to skip gpio-ml-ioh for good, because it is one of the
> few remaining drivers that use the legacy PCI PM interfaces.  We are
> very close to being able to remove a significant amount of ugly code
> from the PCI core.

Makes sense (1).

> gpio-ml-ioh and gpio-pch do look quite similar, and no doubt it would
> be great to unify them.  But without datasheets or hardware to test,

Datasheets are publicly available (at least one may google and find some
information about those PCH chips). I have in possession the hardware for
gpio-pch. I can easily test that part at least.

> that's not a trivial task, and I don't think that burden should fall
> on anyone who wants to make any improvements to these drivers.

> Another alternative would be to remove legacy PCI PM usage
> (ioh_gpio_suspend() and ioh_gpio_resume()) from gpio-ml-ioh.  That
> would mean gpio-ml-ioh wouldn't support power management at all, which
> isn't a good thing, but maybe it would be even more motivation to
> unify it with gpio-pch (which has already been converted by
> 226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"))?

With regard to (1) probably we may exceptionally accept the fix to gpio-ml-ioh,
but I really prefer to do the much more _useful_ job on it by unifying the two.

-- 
With Best Regards,
Andy Shevchenko

Re: [Linux-kernel-mentees] [PATCH v1] gpio: ml: ioh: Convert to dev_pm_ops

[Bjorn Helgaas]

On Mon, Jul 12, 2021 at 02:48:12PM +0300, Andy Shevchenko wrote:
> On Thu, Jul 08, 2021 at 04:47:06PM -0500, Bjorn Helgaas wrote:
> > On Thu, Apr 02, 2020 at 11:23:27PM +0300, Andy Shevchenko wrote:
> > > On Thu, Apr 2, 2020 at 11:16 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > > On Thu, Apr 02, 2020 at 09:33:46PM +0300, Andy Shevchenko wrote:
> > > > > On Thu, Apr 2, 2020 at 6:52 PM Vaibhav Gupta <vaibhavgupta40@gmail.com> wrote:
> > > > > >
> > > > > > Convert the legacy callback .suspend() and .resume()
> > > > > > to the generic ones.
> > > > >
> > > > > Thank you for the patch.
> > > > >
> > > > > Rather then doing this I think the best approach is to unify gpio-pch
> > > > > and gpio-ml-ioh together.
> > > > > Under umbrella of the task, the clean ups like above are highly
> > > > > appreciated.
> > > >
> > > > I'd be all in favor of that, but what Vaibhav is working toward is
> > > > eliminating use of legacy PM in PCI drivers.  I think unifying drivers
> > > > is really out of scope for that project.
> > > >
> > > > If you'd rather leave gpio-ml-ioh.c alone for now, I suggest that
> > > > Vaibhav move on to other PCI drivers that use legacy PM.  If we
> > > > convert all the others away from legacy PM and gpio-ml-ioh.c is the
> > > > only one remaining, then I guess we can revisit this :)
> > > 
> > > Then skip this driver for good.
> > > 
> > > > Or, maybe converting gpio-ml-ioh.c now, along the lines of
> > > > 226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"), would be one small
> > > > step towards the eventual unification, by making gpio-pch and
> > > > gpio-ml-ioh a little more similar.
> > > 
> > > I think it will delay the real work here (very old code motivates
> > > better to get rid of it then semi-fixed one).
> > 
> > With respect, I think it is unreasonable to use the fact that
> > gpio-ml-ioh and gpio-pch should be unified to hold up the conversion
> > of gpio-ml-ioh to generic power management.
> > 
> > I do not want to skip gpio-ml-ioh for good, because it is one of the
> > few remaining drivers that use the legacy PCI PM interfaces.  We are
> > very close to being able to remove a significant amount of ugly code
> > from the PCI core.
> 
> Makes sense (1).
> 
> > gpio-ml-ioh and gpio-pch do look quite similar, and no doubt it would
> > be great to unify them.  But without datasheets or hardware to test,
> 
> Datasheets are publicly available (at least one may google and find some
> information about those PCH chips). I have in possession the hardware for
> gpio-pch. I can easily test that part at least.

If you have a URL for those datasheets, can you share it?  I spent
some time looking but all I found was 1-2 page marketing brochures.

> > that's not a trivial task, and I don't think that burden should fall
> > on anyone who wants to make any improvements to these drivers.
> 
> > Another alternative would be to remove legacy PCI PM usage
> > (ioh_gpio_suspend() and ioh_gpio_resume()) from gpio-ml-ioh.  That
> > would mean gpio-ml-ioh wouldn't support power management at all, which
> > isn't a good thing, but maybe it would be even more motivation to
> > unify it with gpio-pch (which has already been converted by
> > 226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"))?
> 
> With regard to (1) probably we may exceptionally accept the fix to
> gpio-ml-ioh, but I really prefer to do the much more _useful_ job on
> it by unifying the two.

Should Vaibhav re-post this patch, or do you want to pull it from the
archives?  I just checked and it still applies cleanly to v5.14-rc1.

Here it is for reference:
  https://lore.kernel.org/lkml/20200402155057.30667-1-vaibhavgupta40@gmail.com/

I'll post a couple small patches toward unifying them.  They don't do
the whole job but they're baby steps.

Bjorn

Re: [Linux-kernel-mentees] [PATCH v1] gpio: ml: ioh: Convert to dev_pm_ops

[Andy Shevchenko]

On Tue, Jul 13, 2021 at 1:36 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Mon, Jul 12, 2021 at 02:48:12PM +0300, Andy Shevchenko wrote:
> > On Thu, Jul 08, 2021 at 04:47:06PM -0500, Bjorn Helgaas wrote:
> > > On Thu, Apr 02, 2020 at 11:23:27PM +0300, Andy Shevchenko wrote:

...

> > Datasheets are publicly available (at least one may google and find some
> > information about those PCH chips). I have in possession the hardware for
> > gpio-pch. I can easily test that part at least.
>
> If you have a URL for those datasheets, can you share it?  I spent
> some time looking but all I found was 1-2 page marketing brochures.

It's a part of the so called EG20T PCH. It's part of in particular
Intel Galileo (Quark SoC) and Intel Minnowboard (v1) (Atom E6xx SoC).
Hence the easily found links:

http://minnowboard.outof.biz/MinnowBoard.html
https://www.elinux.org/Minnowboard:Minnow_Original
https://en.wikipedia.org/wiki/List_of_Intel_Atom_microprocessors

https://www.intel.com/content/www/us/en/embedded/products/quark/x1000/documentation.html?grouping=EMT_Content%20Type&sort=title:asc
(Chapter 19)

https://ark.intel.com/content/www/us/en/ark/products/codename/37567/products-formerly-tunnel-creek.html

Hmm... Funny, the document #324211 can't be downloaded
https://download.intel.com/embedded/chipsets/datasheet/324211.pdf

I guess you may ping Intel and tell them that they should play nice
when talking about "open hardware" (MinnowBoard initiative).
Nevertheless, the (Old? #457798 is a specification update under NDA.
Okay, it refers to rev 8, while Mouser, see below, provides rev 9)
copy is available on other sites, such as

https://www.mouser.tw/pdfdocs/Intel_Platform_Controller_Hub_EG20T_datasheet.pdf
(Chapter 16)

> > > that's not a trivial task, and I don't think that burden should fall
> > > on anyone who wants to make any improvements to these drivers.
> >
> > > Another alternative would be to remove legacy PCI PM usage
> > > (ioh_gpio_suspend() and ioh_gpio_resume()) from gpio-ml-ioh.  That
> > > would mean gpio-ml-ioh wouldn't support power management at all, which
> > > isn't a good thing, but maybe it would be even more motivation to
> > > unify it with gpio-pch (which has already been converted by
> > > 226e6b866d74 ("gpio: pch: Convert to dev_pm_ops"))?
> >
> > With regard to (1) probably we may exceptionally accept the fix to
> > gpio-ml-ioh, but I really prefer to do the much more _useful_ job on
> > it by unifying the two.
>
> Should Vaibhav re-post this patch, or do you want to pull it from the
> archives?  I just checked and it still applies cleanly to v5.14-rc1.
>
> Here it is for reference:
>   https://lore.kernel.org/lkml/20200402155057.30667-1-vaibhavgupta40@gmail.com/

I'll take from the archives.

> I'll post a couple small patches toward unifying them.  They don't do
> the whole job but they're baby steps.

Thanks! I look forward to seeing them soon!

-- 
With Best Regards,
Andy Shevchenko