Subject: [PATCH] ARM: pxa: Fix pxa3xx-u2d crash when ULPI not used

From: [email-masked] (Igor Grinberg)
Date: Sun, 05 Sep 2010 11:35:33 +0300

On 09/05/10 11:25, Marek Vasut wrote:
> Dne Ne 5. z??? 2010 10:16:48 Igor Grinberg napsal(a):
>>  On 09/05/10 11:01, Marek Vasut wrote:
>>> Dne Ne 5. z??? 2010 09:54:31 Igor Grinberg napsal(a):
>>>>  On 09/03/10 23:35, Marek Vasut wrote:
>>>>> In case the pxa3xx-u2d driver isn't used, probing of ohci-pxa27x will
>>>>> cause an ugly kernel crash (NULL pointer dereference in
>>>>> pxa3xx_u2d_start_hc(), because struct u2d is NULL and clk_enable() call
>>>>> will crash the kernel, trying to access it).
>>>> ohci code checks for pxa3xx cpu and only then runs start/stop hc.
>>> Exactly ... and in case "struct pxa3xx_u2d_ulpi *u2d" is NULL, clk_enable
>>> will crash the kernel.
>>>
>>>> pxa3xx_ulpi.c is compiled if CONFIG_PXA3xx is selected.
>>>> The device <-> driver binding should not be a problem, so the
>>>> pxa3xx_u2d_probe() will run.
>>>> The only case, I see, when struct u2d does not exist is failure of the
>>>> probe function. If this is the case, we are having an abnormal execution
>>>> and if your patch is dealing with this issue, shouldn't you comment it
>>>> as such?
>>> Not at all ... if the pxa3xx-u2d driver isn't loaded at all, the function
>>> (start/stop hc) is still called, but struct pxa3xx_u2d_ulpi *u2d is NULL.
>>> In this case, if you call clk_enable(u2d->clk), you crash the kernel
>>> (because u2d is NULL).
>> How, can it happen, that "pxa3xx-u2d driver isn't loaded at all"?
>> This can happen only if you rip out the device registration or hack a
>> Makefile. I don't see any other way... is there?
> If you don't call pxa3xx_set_u2d_info() ?

Oh... right.
I've added it this way, so boards can control u2d existence and forgot it is there...
Buggy me... :(

Thanks.

>>> Good night, I'll be back in 8 hrs or so :)

Good night indeed :)

>>>>> Signed-off-by: Marek Vasut <[email-masked]>
>>>>> ---
>>>>>
>>>>>  arch/arm/mach-pxa/pxa3xx-ulpi.c |    8 ++++++++
>>>>>  1 files changed, 8 insertions(+), 0 deletions(-)
>>>>>
>>>>> diff --git a/arch/arm/mach-pxa/pxa3xx-ulpi.c
>>>>> b/arch/arm/mach-pxa/pxa3xx-ulpi.c index e57439e..ce7168b 100644
>>>>> --- a/arch/arm/mach-pxa/pxa3xx-ulpi.c
>>>>> +++ b/arch/arm/mach-pxa/pxa3xx-ulpi.c
>>>>> @@ -252,6 +252,10 @@ int pxa3xx_u2d_start_hc(struct usb_bus *host)
>>>>>
>>>>>  {
>>>>>  
>>>>>  	int err = 0;
>>>>>
>>>>> +	/* In case the PXA3xx ULPI isn't used, do nothing. */
>>>>> +	if (!u2d)
>>>>> +		return 0;
>>>>> +
>>>>>
>>>>>  	clk_enable(u2d->clk);
>>>>>  	
>>>>>  	if (cpu_is_pxa310()) {
>>>>>
>>>>> @@ -264,6 +268,10 @@ int pxa3xx_u2d_start_hc(struct usb_bus *host)
>>>>>
>>>>>  void pxa3xx_u2d_stop_hc(struct usb_bus *host)
>>>>>  {
>>>>>
>>>>> +	/* In case the PXA3xx ULPI isn't used, do nothing. */
>>>>> +	if (!u2d)
>>>>> +		return;
>>>>> +
>>>>>
>>>>>  	if (cpu_is_pxa310())
>>>>>  	
>>>>>  		pxa310_stop_otg_hc();

-- 
Regards,
Igor.