Re: [PATCHv3] dmaengine: cppi41: Fix oops in cppi41_runtime_resume

[Bin Liu <b-liu-l0cyMroinI0@public.gmane.org>]

On Tue, Jan 17, 2017 at 09:55:24AM -0800, Tony Lindgren wrote:
> Commit fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
> together with recent MUSB changes allowed USB and DMA on BeagleBone to idle
> when no cable is connected. But looks like few corner case issues still
> remain.
> 
> Looks like just by re-plugging USB cable about ten or so times on BeagleBone
> when configured in USB peripheral mode we can get warnings and eventually
> trigger an oops in cppi41 DMA:
> 
> WARNING: CPU: 0 PID: 14 at drivers/dma/cppi41.c:1154 cppi41_runtime_suspend+
> x28/0x38 [cppi41]
> ...
> 
> WARNING: CPU: 0 PID: 14 at drivers/dma/cppi41.c:452
> push_desc_queue+0x94/0x9c [cppi41]
> ...
> 
> Unable to handle kernel NULL pointer dereference at virtual
> address 00000104
> pgd = c0004000
> [00000104] *pgd=00000000
> Internal error: Oops: 805 [#1] SMP ARM
> ...
> [<bf0d92cc>] (cppi41_runtime_resume [cppi41]) from [<c0589838>]
> (__rpm_callback+0xc0/0x214)
> [<c0589838>] (__rpm_callback) from [<c05899ac>] (rpm_callback+0x20/0x80)
> [<c05899ac>] (rpm_callback) from [<c0589460>] (rpm_resume+0x504/0x78c)
> [<c0589460>] (rpm_resume) from [<c058a1a0>] (pm_runtime_work+0x60/0xa8)
> [<c058a1a0>] (pm_runtime_work) from [<c0156120>] (process_one_work+0x2b4/0x808)
> 
> This is because of a race with runtime PM and cppi41_dma_issue_pending()
> as reported by Alexandre Bailon <abailon-rdvid1DuHRBWk0Htik3J/w@public.gmane.org> in earlier
> set of patches. Based on mailing list discussions we however came to the
> conclusion that a different fix from Alexandre's fix is needed in order
> to guarantee that DMA is really active when we try to use it.
> 
> To fix the issue, we need to add a driver specific flag as we otherwise
> can have -EINPROGRESS state set by runtime PM and can't rely on
> pm_runtime_active() to tell us when we can use the DMA.
> 
> And we need to make sure the DMA transfers get triggered in the queued
> order. So let's always queue the transfers, then flush the queue
> from both cppi41_dma_issue_pending() and cppi41_runtime_resume()
> as suggested by Grygorii Strashko <grygorii.strashko-l0cyMroinI0@public.gmane.org> in an
> earlier example patch.
> 
> For reference, this is also documented in Documentation/power/runtime_pm.txt
> in the example at the end of the file as pointed out by Grygorii Strashko
> <grygorii.strashko-l0cyMroinI0@public.gmane.org>.
> 
> Based on earlier patches from Alexandre Bailon <abailon-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>
> and Grygorii Strashko <grygorii.strashko-l0cyMroinI0@public.gmane.org> modified based on
> testing and what was discussed on the mailing lists.
> 
> Note that additional patches are still needed depending on how we want
> to handle the cppi41 runtime PM. So far cppi41 is always coupled with
> musb driver, and musb guarantees that cppi41 is always active during
> use. So until we have a better solution, let's just set the cppi41
> autosuspend delay 1 second to avoid pointless EINPROGRESS warnings during
> USB mass storage enumeration. As cppi41 is properly clocked with musb
> being active, we can safely do this.
> 
> Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
> Cc: Andy Shevchenko <andy.shevchenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Bin Liu <b-liu-l0cyMroinI0@public.gmane.org>
> Cc: Grygorii Strashko <grygorii.strashko-l0cyMroinI0@public.gmane.org>
> Cc: Kevin Hilman <khilman-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>
> Cc: Patrick Titiano <ptitiano-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>
> Cc: Sergei Shtylyov <sergei.shtylyov-M4DtvfQ/ZS1MRgGoP+s0PdBPR1lH4CV8@public.gmane.org>
> Reported-by: Alexandre Bailon <abailon-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>
> Signed-off-by: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>

With this v3, I still get -71 error when a device is plugged to a hub to
musb. It doesn't happen though if the device is already plugged to the hub
before attaching the hub to musb.

[  177.579300] usb 1-1: reset high-speed USB device number 2 using musb-hdrc
[  177.719308] usb 1-1: device descriptor read/64, error -71
[  178.350297] usb 1-1.1: new high-speed USB device number 4 using musb-hdrc

And I still get -115 error flooding with thumb drive.

[  236.880068] cppi41-dma-engine 47400000.dma-controller: cppi41_irq pm runtime get: -115

I tested with TI AM335x GP EVM. The problems happen on both musb ports.

Regards,
-Bin.
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