Re: [RFC/RFT][PATCH v3 0/5] Functional dependencies between devices

[Marek Szyprowski]

Hi Everyone,

On 2016-09-16 09:25, Marek Szyprowski wrote:
> Hi Rafael,
>
> On 2016-09-16 00:03, Rafael J. Wysocki wrote:
> > Hi Everyone,
> >
> > On Thursday, September 08, 2016 11:25:44 PM Rafael J. Wysocki wrote:
> > > Hi Everyone,
> > >
> > > This is a refresh of the functional dependencies series that I 
> > > posted last
> > > year and which has picked up by Marek quite recently.  For 
> > > reference, appended
> > > is my introductory message sent previously (which may be slightly 
> > > outdated now).
> > >
> > > As last time, the first patch rearranges the code around 
> > > __device_release_driver()
> > > a bit to prepare it for the next one (it actually hasn't changed 
> > > AFAICS).
> > >
> > > The second patch introduces the actual device links mechanics, but 
> > > without
> > > system suspend/resume and runtime PM support which are added by the 
> > > subsequent
> > > patches.
> > >
> > > Some bugs found by Marek during his work on these patches should be 
> > > fixed
> > > here.  In particular, the endless recursion in device_reorder_to_tail()
> > > which simply was broken before.
> > >
> > > There are two additional patches to address the issue with runtime 
> > > PM support
> > > that occured when runtime PM was disabled for some suppliers due to 
> > > a PM
> > > sleep transition in progress.  Those patches simply make runtime PM 
> > > helpers
> > > return 0 in that case which may be controversial, so please let me 
> > > know if
> > > there are concerns about those.
> > >
> > > The way device_link_add() works is a bit different, as it takes an 
> > > additional
> > > status argument now.  That makes it possible to create a link in any 
> > > state,
> > > with extra care of course, and should address the problem pointed to 
> > > by Lukas
> > > during the previous discussion.
> > >
> > > Also some comments from Tomeu have been addressed.
> > An update here.
> >
> > The first patch hasn't changed, so I'm resending it.
> >
> > The majority of changes in the other patches are in order to address 
> > Lukas'
> > comments.
> >
> > First off, I added a DEVICE_LINK_STATELESS flag that will prevent the 
> > driver
> > core from trying to maintain device links having it set.
> >
> > Also, the DEVICE_LINK_PERSISTENT flag was dropped (as link 
> > "persistence" is the
> > default behavior now) and there's a new one, DEVICE_LINK_AUTOREMOVE, 
> > that will
> > cause the driver core to remove the link on the consumer driver unbind.
> >
> > Moreover, the code checks attempts to create a link between a parent 
> > and a child
> > device now and actively prevents that from happening.
> >
> > The changelog of the second patch has been updated as requested by Ulf.
> >
> > The third patch was updated to fix a bug related to the (previously 
> > missing)
> > clearing of power.direct_complete for supplier devices having 
> > consumers that
> > don't use direct_complete.
> >
> > The next two (runtime PM) patches turned out to be unnecessary, so 
> > I've dropped
> > them.
> >
> > The runtime PM patch [4/5] was reorganized somewhat to reduce the 
> > indentation
> > level in there, but the code flow introduced by it is essentially the 
> > same
> > and the last patch was simply rebased on top of the new series.
> >
> > If this version still works for Marek, I'll probably drop the RFC tag 
> > from it
> > in the next iteration.
>
> Sadly, this version doesn't work. I get following kernel bug:
>
> [    2.357622] BUG: spinlock bad magic on CPU#0, swapper/0/1
> [    2.362361]  lock: 0xeea2e294, .magic: ffffffff, .owner: /0, 
> .owner_cpu: -1
> [    2.369389] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 
> 4.8.0-rc6-00019-gd66d0028dd3c-dirty #651
> [    2.377954] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [    2.384053] [<c010d7f0>] (unwind_backtrace) from [<c010a4b4>] 
> (show_stack+0x10/0x14)
> [    2.391766] [<c010a4b4>] (show_stack) from [<c032220c>] 
> (dump_stack+0x74/0x94)
> [    2.398970] [<c032220c>] (dump_stack) from [<c0158e8c>] 
> (do_raw_spin_lock+0x160/0x1a8)
> [    2.406870] [<c0158e8c>] (do_raw_spin_lock) from [<c03e8d84>] 
> (device_links_no_driver+0x64/0x98)
> [    2.415634] [<c03e8d84>] (device_links_no_driver) from [<c03ec32c>] 
> (driver_probe_device+0xa0/0x2bc)
> [    2.424744] [<c03ec32c>] (driver_probe_device) from [<c03ec5f4>] 
> (__driver_attach+0xac/0xb0)
> [    2.433165] [<c03ec5f4>] (__driver_attach) from [<c03eaa90>] 
> (bus_for_each_dev+0x54/0x88)
> [    2.441323] [<c03eaa90>] (bus_for_each_dev) from [<c03eba6c>] 
> (bus_add_driver+0xe8/0x1f4)
> [    2.449481] [<c03eba6c>] (bus_add_driver) from [<c03ece54>] 
> (driver_register+0x78/0xf4)
> [    2.457469] [<c03ece54>] (driver_register) from [<c010178c>] 
> (do_one_initcall+0x3c/0x16c)
> [    2.465632] [<c010178c>] (do_one_initcall) from [<c0b00d84>] 
> (kernel_init_freeable+0x120/0x1ec)
> [    2.474313] [<c0b00d84>] (kernel_init_freeable) from [<c0704194>] 
> (kernel_init+0x8/0x118)
> [    2.482470] [<c0704194>] (kernel_init) from [<c01079b8>] 
> (ret_from_fork+0x14/0x3c)
>
> I'm checking what's wrong there.

The issue was caused by missing braces in device_links_no_driver() 
function.
After fixing it the patches works fine, so you can add:

Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

Rafael, how and when do you plan to merge them? I would like to know how to
process further with my IOMMU patch, which is depends on your patches.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland