Re: STANDBY IMMEDIATE failed on NVIDIA MCP5x controllers when system suspend

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On Tue, 2013-03-12 at 10:53 +0800, Aaron Lu wrote:
> Hi James and Alan,
> 
> On 03/11/2013 11:00 PM, Alan Stern wrote:
> > On Mon, 11 Mar 2013, James Bottomley wrote:
> > 
> >> Oh, that seems to be the suspend order isn't careful enough.
> >> __device_suspend() waits for its children, but the host disk are too far
> >> separated in the device tree.  If the immediate children of the host are
> >> all sync, that wait never actually waits for anything.
> > 
> > I was going to make exactly this same point.  During async suspend, the
> > PM core is careful to make sure that no device is suspended before its
> > children.  But there aren't any other checks, so if device A isn't an
> > ancestor of device B then it's possible for async suspend to power down
> > A before B.  This can cause problems if B needs A to be active while B
> > is suspending.
> 
> Thanks for the suggestions.
> 
> > 
> > Does the ATA system have any non-ancestor dependencies like this?  If 
> > it does, the appropriate driver can be fixed to take them into account.
> 
> I don't think there is, and the relationship is like this:
> 
>     ata_host_controller* (named sata_nv xxx)
> 	    |
> 	ata_port* (named atax, while "ata_port atax" is another device)
> 	/	\
> scsi_host	ata_link
>     |		   |
> scsi_target	ata_device
>     |
> scsi_device* (named sd x:x:x:x)
> 
> With the devices that have actual PM operation functions defined have
> the asterisk next to it.
> 
> So ata_host_controller waits for all of the ata_ports, and the ata_port
> waits for both scsi_host and ata_link. scsi_host waits for scsi_target,
> and scsi_target waits for scsi_device. So if scsi_device is not done,
> ata_port will not start. Doesn't look like a problem to me.
> 
> And from the log:
> https://bugzilla.kernel.org/attachment.cgi?id=95101
> It also looks like the order is correct.

That's not what that log appears to say.  Here are the relevant bits

[ 7377.813634] sd 2:0:0:0: async_suspend: scheduled
[ 7377.813636] sd 2:0:0:0: __device_suspend: starts
[ 7377.813639] sd 2:0:0:0: [sdb] Synchronizing SCSI cache
... so now we've begun suspend]
[ 7377.813750] sd 2:0:0:0: [sdb] Stopping disk
[... here we send STANDBY IMMEDIATE ]
[ 7378.237627] sata_nv 0000:00:05.2: async_suspend: scheduled
[ 7378.237631] sata_nv 0000:00:05.2: __device_suspend: starts
[... we begin to shut down the host ]
[ 7378.249333] sata_nv 0000:00:05.2: __device_suspend: done
[... host shutdown complete ]
[ 7408.372642] ata3.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[ 7408.372647] ata3.00: failed command: STANDBY IMMEDIATE
[ ... command times out ]
[ 7408.870675] dpm_run_callback(): scsi_bus_suspend+0x0/0x20 [scsi_mod] returns 134217730
[ 7408.870681] sd 2:0:0:0: __device_suspend: done

We shut down the host controller before the command completed.  This
appears to cause the timeout

James


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