linux-kernel - Re: [PATCH v2 1/1] usb: ulpi: ulpi_init should be executed in subsys

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Date:	Fri, 22 May 2015 13:07:08 +0300
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	"Lu, Baolu" <baolu.lu@...ux.intel.com>
Cc:	David Cohen <david.a.cohen@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	qiuxu.zhuo@...el.com, Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH v2 1/1] usb: ulpi: ulpi_init should be executed in
 subsys_initcall

> >>>Many drivers and modules depend on ULPI bus registeration to
> >>>register ULPI interfaces and drivers. It's more appropriate
> >>>to register ULPI bus in subsys_initcall instead of module_init.
> >>>
> >>>Kernel panic has been reported with some kind of kernel config.
> >>Even though I agree subsys_initcall is better to register ulpi bus, it's
> >>still no excuse to have kernel panic. What about ULPI bus being compiled
> >>as module?
> 
> No kernel panic if ULPI is built as a module.
> 
> >>IMHO this is avoiding the proper kernel panic fix which should be
> >>failing gracefully (or defer probe) from tusb1210 driver.
> >Maybe I need to express myself better :)
> >IMHO we should not consider work done with this patch only. It's still
> >incomplete.
> 
> I am with you on that we should know the real problem.
> 
> I could go ahead with further debugging. Do you have any suggestions
> about which direction should I go?

This patch does not address all the cases where the panic may occur,
like the case where the bus itself fails register, while Sasha's patch
does. For the panic, we'll use Sasha's patch. I though we were clear
on this.

This patch addresses an issue with the load order. Even with the panic
fixed, we still may end up loading the drivers depending on the bus,
i.e. ulpi phy drivers or the ulpi interface providers, before the bus.
That is a different issue, but we need to fix it as well.

To fix the panic, you can already pick Sasha's patch titled:
"usb: ulpi: don't register drivers if bus doesn't exist"

Baolu, please fix the commit message to explain this patch is fixing
the problem with the load order.


Thanks,

-- 
heikki
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