From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from am1outboundpool.messaging.microsoft.com (am1ehsobe005.messaging.microsoft.com [213.199.154.208]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Microsoft Secure Server Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id CE2332C00AC for ; Wed, 5 Dec 2012 20:28:46 +1100 (EST) Message-ID: <50BF13E1.1000009@freescale.com> Date: Wed, 5 Dec 2012 17:29:05 +0800 From: Chen Yuanquan-B41889 MIME-Version: 1.0 To: Benjamin Herrenschmidt Subject: Re: [linuxppc-release][PATCH] powerpc/pci-hotplug: fix init issue of rescanned pci device References: <1354674717-14426-1-git-send-email-B41889@freescale.com> <1354691878.2351.2.camel@pasglop> <50BF03C1.2070304@freescale.com> <1354695989.2351.13.camel@pasglop> In-Reply-To: <1354695989.2351.13.camel@pasglop> Content-Type: text/plain; charset="UTF-8"; format=flowed Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, r61911@freescale.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 12/05/2012 04:26 PM, Benjamin Herrenschmidt wrote: > On Wed, 2012-12-05 at 16:20 +0800, Chen Yuanquan-B41889 wrote: >> On 12/05/2012 03:17 PM, Benjamin Herrenschmidt wrote: >>> On Wed, 2012-12-05 at 10:31 +0800, Yuanquan Chen wrote: >>>> On powerpc arch, some fixup work of PCI/PCI-e device is just done during the >>>> first scan at booting time. For the PCI/PCI-e device rescanned after linux OS >>>> booting up, the fixup work won't be done, which leads to dma_set_mask error or >>>> irq related issue in rescanned PCI/PCI-e device's driver. So, it does the same >>>> fixup work for the rescanned device to avoid this issue. >>> Hrm, the patch is a bit gross. First the code shouldn't be copy/pasted >>> that way but factored out. > Please, at least format your email properly so I can try to undertand > without needing aspirin. > >> There's a judgement "if (!bus->is_added)" before calling of >> pcibios_fixup_bus in pci_scan_child_bus, so for the rescanned device, >> the fixup won't execute, which leads to fatal error in driver of rescanned >> device on freescale powerpc, no this issues on x86 arch. > First, none of that invalidates my statement that you shouldn't > duplicate a whole block of code like this. Even if your approach is > correct (which is debated separately), at the very least you should > factor the code out into a common function between the two copies. > >> Remove the judgement, let it to do the pcibios_fixup_bus >> directly, the error won't occur for the rescanned device. But it's >> general code, not proper to change here, so copy the pcibios_fixup_bus >> work to pcibios_enable_device. >> >>> I'm surprised also that is_added is false when pcibios_enable_device() >>> gets called ... that looks strange to me. At what point is that enable >>> happening in the hotplug sequence ? >> All devices are rescanned and then call the pci_enable_devices and >> pci_bus_add_devices. > Where ? How ? What is the sequence happening ? In any case, I think if > we need a proper fixup done per-device like that after scan we ought to > create a new hook at the generic level rather than that sort of hack. > echo 1 > rescan to trigger dev_rescan_store: dev_rescan_store->pci_rescan_bus->pci_scan_child_bus, pci_assign_unassigned_bus_resources, pci_enable_bridges, pci_bus_add_devices pci_enable_bridges->pci_enable_device->__pci_enable_device_flags->do_pci_enable_device-> pcibios_enable_device pci_bus_add_devices->pci_bus_add_device->"dev->is_added = 1" Yeah, it's general fixup code for every rescanned PCI/PCI-e device on powerpc at runtime. So if we want to call it in a ppc_md member, we need to wrap it as a function and assign it in every ppc_md, it isn't proper for the general code. Regards, yuanquan >> The patch code will be called by pci_enable_devices. The "dev->is_added" >> is set in pci_bus_add_device >> which is called by pci_bus_add_devices. So "dev->is_added" is false when >> checking it in pcibios_enable_device >> for the rescanned device. > Who calls pci_enable_device() in the rescan case ? Why isn't it left to > the driver ? I don't think we can rely on that behaviour not to change. > >>> How do you trigger the rescan anyway ? >> Use the interface under /sys : >> echo 1 > /sys/bus/pci/devices/xxx/remove >> >> then echo 1 to the pci device which is the bus of the removed device >> echo 1 > /sys/bus/pci/devices/xxxx/rescan >> the removed device will be scanned and it's driver module will be loaded >> automatically. > Yeah this code path are known to be fishy. I think the problem is at the > generic abstraction level and that's where it needs to be fixed. > > Cheers, > Ben. > >> Regards, >> yuanquan >>> I think the problem needs to be solve at a higher level, I'm adding >>> linux-pci & Bjorn to the CC list. >>> >>> Cheers, >>> Ben. >>> >>>> Signed-off-by: Yuanquan Chen >>>> --- >>>> arch/powerpc/kernel/pci-common.c | 20 ++++++++++++++++++++ >>>> 1 file changed, 20 insertions(+) >>>> >>>> diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c >>>> index 7f94f76..f0fb070 100644 >>>> --- a/arch/powerpc/kernel/pci-common.c >>>> +++ b/arch/powerpc/kernel/pci-common.c >>>> @@ -1496,6 +1496,26 @@ int pcibios_enable_device(struct pci_dev *dev, int mask) >>>> if (ppc_md.pcibios_enable_device_hook(dev)) >>>> return -EINVAL; >>>> >>>> + if (!dev->is_added) { >>>> + /* >>>> + * Fixup NUMA node as it may not be setup yet by the generic >>>> + * code and is needed by the DMA init >>>> + */ >>>> + set_dev_node(&dev->dev, pcibus_to_node(dev->bus)); >>>> + >>>> + /* Hook up default DMA ops */ >>>> + set_dma_ops(&dev->dev, pci_dma_ops); >>>> + set_dma_offset(&dev->dev, PCI_DRAM_OFFSET); >>>> + >>>> + /* Additional platform DMA/iommu setup */ >>>> + if (ppc_md.pci_dma_dev_setup) >>>> + ppc_md.pci_dma_dev_setup(dev); >>>> + >>>> + /* Read default IRQs and fixup if necessary */ >>>> + pci_read_irq_line(dev); >>>> + if (ppc_md.pci_irq_fixup) >>>> + ppc_md.pci_irq_fixup(dev); >>>> + } >>>> return pci_enable_resources(dev, mask); >>>> } >>>> >>> >>> >>> > > > >