From mboxrd@z Thu Jan 1 00:00:00 1970 From: grinberg@compulab.co.il (Igor Grinberg) Date: Sun, 05 Sep 2010 16:46:14 +0300 Subject: [PATCH] ARM: pxa: Fix pxa3xx-u2d crash when ULPI not used In-Reply-To: References: <1283546146-20000-1-git-send-email-marek.vasut@gmail.com> <201009051001.22816.marek.vasut@gmail.com> <4C8351F0.2040801@compulab.co.il> <201009051025.49256.marek.vasut@gmail.com> <4C835655.1080103@compulab.co.il> Message-ID: <4C839F26.4050107@compulab.co.il> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 09/05/10 13:43, Eric Miao wrote: > On Sun, Sep 5, 2010 at 4:35 PM, Igor Grinberg wrote: >> 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... :( >> > Igor, > > So do you this as a proper fix, or there is better way out? If we want to keep it the most straight-forward way so it is fine. Another possible ways would be: 1) create a new flag, lets say PORT2_USE_U2DC in pxaohci_platform_data. This is a relatively clean way of making ohci aware of u2d existence at runtime and eliminates the calls to functions of non-existing (not loaded) driver... 2) use something like: struct u2d_hc_ops { int (*start_hc)(...); void (*stop_hc)(...); } in board init code register the ops structure via the pxa_ohci platform data. This way adds some more pollution to the pxa_ohci glue with code relevant only to pxa3xx, achieving the same as the 1st way, but also can be useful for u2dc otg/peripheral driver (if it will come some day...). I'm fine with both (Marek's patch or my proposal), so tell me what looks better to you. -- Regards, Igor.