Messages in this thread | | | Date | Fri, 10 Oct 2014 11:46:50 -0400 | From | Santosh Shilimkar <> | Subject | Re: [PATCH] ARM: keystone: add bus notifier to set dma_pfn_offset for pci devices |
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On 10/10/14 11:42 AM, Russell King - ARM Linux wrote: > On Fri, Oct 10, 2014 at 11:29:03AM -0400, Santosh Shilimkar wrote: >> >> >> On 10/10/14 11:15 AM, Murali Karicheri wrote: >>> When PCI device driver such as that for e1000e tries to set dma mask >>> using dma_set_mask_and_coherent(), it fails because the dma_pfn_offset >>> is incorrect on a Keystone SoC. This patch fix this by adding a bus >>> notifier to set this correctly for PCI devices. >>> >>> Signed-off-by: Murali Karicheri <m-karicheri2@ti.com> >>> --- >> Looks good. I will pick this up after the merge window. > > No it doesn't, this patch is crap. Really. Let's look again at what the > patch is doing: > > if (platform_nb.notifier_call) > bus_register_notifier(&platform_bus_type, &platform_nb); > + if (platform_nb.notifier_call) > + bus_register_notifier(&pci_bus_type, &platform_nb); > > Notice that both calls are using the same platform_nb structure, which is: > > static struct notifier_block platform_nb; > > and in turn this is: > > struct notifier_block { > notifier_fn_t notifier_call; > struct notifier_block __rcu *next; > int priority; > }; > > Notice that "next" pointer - these blocks are used as a single-linked list. > So, this block gets registered for the platform bus, and is inserted into > that bus notifier chain. That means "next" may be set to a non-NULL > next notifier block. > > Then it gets registered against the PCI bus, which *will* overwrite the > next pointer in platform_nb. > Err.... You are dead right. I missed completely that it is using the same notifier block. Sorry for oversight and thanks for spotting it.
Regards, Santosh
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