Hi Joerg, On Tuesday 14 February 2012 11:44:37 Joerg Roedel wrote: > On Mon, Feb 13, 2012 at 09:28:30AM +0800, James wrote: > > >> @@ -28,6 +28,7 @@ obj-$(CONFIG_XEN) += xen/ > > >> > > >> # regulators early, since some subsystems rely on them to initialize > > >> obj-$(CONFIG_REGULATOR) += regulator/ > > >> +obj-$(CONFIG_IOMMU_SUPPORT) += iommu/ > > >> > > >> # tty/ comes before char/ so that the VT console is the boot-time > > >> # default. > > >> @@ -125,7 +126,6 @@ obj-y += clk/ > > >> > > >> obj-$(CONFIG_HWSPINLOCK) += hwspinlock/ > > >> obj-$(CONFIG_NFC) += nfc/ > > >> -obj-$(CONFIG_IOMMU_SUPPORT) += iommu/ > > >> > > >> # Virtualization drivers > > >> obj-$(CONFIG_VIRT_DRIVERS) += virt/ > > I don't see how this patch solves a problem like below. > > > [ 3.663269] Unable to handle kernel NULL pointer dereference at virtual > > address 00000058
[snip] > > [<c03eeac4>] (klist_next+0x10/0xb4) from [<c024deb8>] > > (next_device+0x8/0x14) > > [<c024deb8>] (next_device+0x8/0x14) from [<c024df28>] > > (driver_find_device+0x64/0x7c) > > [<c024df28>] (driver_find_device+0x64/0x7c) from [<c02e9578>] > > (isp_probe+0x228/0xa34) [snip] > This looks more like data corruption or something. But this is definitly > not caused by some random order in the Makefile. > Please debug this issue down to the real cause. Bisecting may help here. There's actually a line missing from the backtrace for some reason. isp_probe() calls iommu_attach_device(), which ends up calling omap_iommu_attach(). That function then calls driver_find_device(), passing it omap_iommu_driver.driver as its first argument. However, as the OMAP3 ISP driver is linked in the kernel before the OMAP3 IOMMU driver, omap_iommu_init() has not be called yet by this time. omap_iommu_driver.driver is thus uninitialized, and klist iteration oopses as the linked list head is NULL. -- Regards, Laurent Pinchart _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
