On Wed, 2016-05-18 at 13:27 +0000, Gavin Guo wrote:
> On Tue, May 17, 2016 at 6:06 PM, Vinod Koul <vinod.koul@xxxxxxxxx>
> wrote:
> >
> > On Mon, May 16, 2016 at 06:08:20PM +0800, Gavin Guo wrote:
> > >
> > > The following error messages can be observed on the Intel
> > > Haswell-E
> > > chipset with v3.13 kernel. After the analysis, I found there is
> > > no
> > > difference in the logic of these error messages in the current
> > > upstream kernel. I also searched the git log and can't find any
> > > commit
> > > which is fix to the error(correct me if I am wrong). The
> > > following is
> > > the detail, and I'll really appreciate if there is any comment.
> > > :)
> > 3.13 is ancient, can you check this on latest kernel
> Thank you for the comment. It's running on the production system.
> However,
> I'll try to figure out if it's possible to test the latest kernel.
I wonder if you don't have the extended PCI config space access enabled
in your kernel config.
>
> >
> >
> > >
> > >
> > > ioatdma 0000:00:04.0: channel error register unreachable
> > > ioatdma 0000:00:04.0: channel enumeration error
> > > ioatdma 0000:00:04.0: Intel(R) I/OAT DMA Engine init failed
> > > ioatdma 0000:00:04.1: channel error register unreachable
> > > ioatdma 0000:00:04.1: channel enumeration error
> > > ioatdma 0000:00:04.1: Intel(R) I/OAT DMA Engine init failed
> > > ...
> > > ioatdma 0000:00:04.7: channel error register unreachable
> > > ioatdma 0000:00:04.7: channel enumeration error
> > > ioatdma 0000:00:04.7: Intel(R) I/OAT DMA Engine init failed
> > > mei_me 0000:00:16.0: initialization failed.
> > >
> > > There are 8 I/OAT DMA controllers on the Haswell-E chipset:
> > > 8086:2f20 ~ 8086:2f27
> > > 80:04.0 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 0 (rev 02)
> > > 80:04.1 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 1 (rev 02)
> > > 80:04.2 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 2 (rev 02)
> > > 80:04.3 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 3 (rev 02)
> > > 80:04.4 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 4 (rev 02)
> > > 80:04.5 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 5 (rev 02)
> > > 80:04.6 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 6 (rev 02)
> > > 80:04.7 System peripheral: Intel Corporation Haswell-E DMA
> > > Channel 7 (rev 02)
> > >
> > > Analysis:
> > > The bug happens when the driver is resetting DMA controller, this
> > > is
> > > the sequence: The function, ioat_pci_probe, is called when the
> > > DMA
> > > controller is detected by the PCI bus. Then,
> > > ioat3_dma_probe -> ioat_probe -> ioat2_enumerate_channels ->
> > > ioat3_reset_hw. The following code can be found in the
> > > ioat3_reset_hw:
> > >
> > > drivers/dma/ioat/dma_v3.c:
> > > chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
> > > writel(chanerr, chan->reg_base + IOAT_CHANERR_OFFSET);
> > > ...
> > > err = pci_read_config_dword(pdev,
> > > IOAT_PCI_CHANERR_INT_OFFSET, &chanerr);
> > > if (err) {
> > > dev_err(&pdev->dev,
> > > "channel error register unreachable\n");
> > > return err;
> > > }
> > >
> > > Obviously, there are something wrong in the channel error
> > > register
> > > reset process. Then all the way back to ioat_probe(). Because the
> > > error happens, the dma->chancnt will be set to 0:
> > >
> > > drivers/dma/ioat/dma.c:
> > > if (!dma->chancnt) {
> > > dev_err(dev, "channel enumeration error\n");
> > > goto err_setup_interrupts;
> > > }
> > >
> > > Finally back to ioat_pci_probe:
> > >
> > > drivers/dma/ioat/pci.c:
> > > err = ioat3_dma_probe(device, ioat_dca_enabled);
> > > else
> > > return -ENODEV;
> > >
> > > if (err) {
> > > dev_err(dev, "Intel(R) I/OAT DMA Engine init
> > > failed\n");
> > > return -ENODEV;
> > --
> > ~Vinod��.n��������+%������w��{.n��������)�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
