Re: [PATCH v2 pci] PCI/MSI: pci-xgene-msi: Enable MSI support in ACPI boot for X-Gene v1

[Khuong Dinh]

Hi Lorenzo,

On Tue, May 9, 2017 at 3:55 PM, Khuong Dinh <kdinh@xxxxxxx> wrote:
> Hi Lorenzo,
>
> On Fri, May 5, 2017 at 9:51 AM, Lorenzo Pieralisi
> <lorenzo.pieralisi@xxxxxxx> wrote:
>> On Thu, May 04, 2017 at 05:36:06PM -0700, Khuong Dinh wrote:
>>> Hi Marc,
>>> There's no explicit dependency between pcie driver and msi
>>> controller.  The current solution that we did is relying on the
>>> node ordering in BIOS.  ACPI 5.0 introduced _DEP method to assign a
>>> higher priority in start ordering.  This method could be applied in
>>> case of msi and pcie are the same level of subsys_init (in ACPI
>>> boot).  However, PCIe driver has not supported for this dependency
>>> check yet.  How do you think about this solution.
>>
>> First off, you can't post emails with confidentiality notices on
>> mailing lists so remove it from now onwards.
>
> Fixed
>
>> Secondly, I commented on this before, so you know what my opinion is.
>
> I got your opinion. I'll implement as your suggestion.
>

  Regarding to your previous suggestion to add a hook walking the ACPI
namespace before acpi_bus_scan() in acpi_scan_init() to make MSI
controllers must be probed before PCI.
  I have a concern that the MSI namespace â _SB.MSIXâ is not a unique
name and how can we walk the ACPI namespace and use this name to make
MSI probed before PCI.
  May you have little bit more information for this or do you have
another suggestion for this?

   Thereâs another solution which makes this simpler and Iâd like to
ask your opinion about this.
   The solution is to make an hierarchy between MSI and PCI nodes  as below:
Device(\_SB.MSIX) {
   Device(\_SB.PCI0)
   Device(\_SB.PCI1)
   ââ
}
  In other word, MSIX node is a parent node of PCI nodes in ACPI table.
  In this sense, thereâs an explicit dependency between MSI and PCI,
MSI controller must be probed before PCI and it will guarantee not
breaking next kernel releases.
  How do you think about this solution.

 I also tried to use _DEP method to describe the dependency of PCIe
nodes, but it looks that it does not work as PCI and MSI are handed by
 acpi_bus_scan and still having issue when we re-probe PCI.

Thanks,
Khuong Dinh

>> Finally, please execute this command on the vmlinux that "works"
>> for you:
>>
>> nm vmlinux | grep -E '__initcall_(xgene_pcie_msi_init|acpi_init)'
>
> $ nm vmlinux | grep -E '__initcall_(xgene_pcie_msi_init|acpi_init)'
> ffff000008dab2d8 t __initcall_acpi_init4
> ffff000008dab2c8 t __initcall_xgene_pcie_msi_init4
>
> Best regards,
> Khuong Dinh
>
>> Even by ordering devices in the ACPI tables (that I abhor) I still do
>> not understand how this works (I mean without relying on kernel link
>> order to ensure that the MSI driver is probed before PCI devices are
>> enumerated in acpi_init()).
>>
>> Thanks,
>> Lorenzo
>>
>>> Best regards,
>>> Khuong
>>>
>>> On Fri, Apr 28, 2017 at 2:27 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>>> > On 28/04/17 01:54, Khuong Dinh wrote:
>>> >> From: Khuong Dinh <kdinh@xxxxxxx>
>>> >>
>>> >> This patch makes pci-xgene-msi driver ACPI-aware and provides
>>> >> MSI capability for X-Gene v1 PCIe controllers in ACPI boot mode.
>>> >>
>>> >> Signed-off-by: Khuong Dinh <kdinh@xxxxxxx>
>>> >> Signed-off-by: Duc Dang <dhdang@xxxxxxx>
>>> >> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>>> >> ---
>>> >> v2:
>>> >>  - Verify with BIOS version 3.06.25 and 3.07.09
>>> >> v1:
>>> >>  - Initial version
>>> >> ---
>>> >>  drivers/pci/host/pci-xgene-msi.c |   35 ++++++++++++++++++++++++++++++++---
>>> >>  1 files changed, 32 insertions(+), 3 deletions(-)
>>> >>
>>> >> diff --git a/drivers/pci/host/pci-xgene-msi.c b/drivers/pci/host/pci-xgene-msi.c
>>> >> index f1b633b..00aaa3d 100644
>>> >> --- a/drivers/pci/host/pci-xgene-msi.c
>>> >> +++ b/drivers/pci/host/pci-xgene-msi.c
>>> >> @@ -24,6 +24,7 @@
>>> >>  #include <linux/pci.h>
>>> >>  #include <linux/platform_device.h>
>>> >>  #include <linux/of_pci.h>
>>> >> +#include <linux/acpi.h>
>>> >>
>>> >>  #define MSI_IR0                      0x000000
>>> >>  #define MSI_INT0             0x800000
>>> >> @@ -39,7 +40,7 @@ struct xgene_msi_group {
>>> >>  };
>>> >>
>>> >>  struct xgene_msi {
>>> >> -     struct device_node      *node;
>>> >> +     struct fwnode_handle    *fwnode;
>>> >>       struct irq_domain       *inner_domain;
>>> >>       struct irq_domain       *msi_domain;
>>> >>       u64                     msi_addr;
>>> >> @@ -249,6 +250,13 @@ static void xgene_irq_domain_free(struct irq_domain *domain,
>>> >>       .free   = xgene_irq_domain_free,
>>> >>  };
>>> >>
>>> >> +#ifdef CONFIG_ACPI
>>> >> +static struct fwnode_handle *xgene_msi_get_fwnode(struct device *dev)
>>> >> +{
>>> >> +     return xgene_msi_ctrl.fwnode;
>>> >> +}
>>> >> +#endif
>>> >> +
>>> >>  static int xgene_allocate_domains(struct xgene_msi *msi)
>>> >>  {
>>> >>       msi->inner_domain = irq_domain_add_linear(NULL, NR_MSI_VEC,
>>> >> @@ -256,7 +264,7 @@ static int xgene_allocate_domains(struct xgene_msi *msi)
>>> >>       if (!msi->inner_domain)
>>> >>               return -ENOMEM;
>>> >>
>>> >> -     msi->msi_domain = pci_msi_create_irq_domain(of_node_to_fwnode(msi->node),
>>> >> +     msi->msi_domain = pci_msi_create_irq_domain(msi->fwnode,
>>> >>                                                   &xgene_msi_domain_info,
>>> >>                                                   msi->inner_domain);
>>> >>
>>> >> @@ -265,6 +273,9 @@ static int xgene_allocate_domains(struct xgene_msi *msi)
>>> >>               return -ENOMEM;
>>> >>       }
>>> >>
>>> >> +#ifdef CONFIG_ACPI
>>> >> +     pci_msi_register_fwnode_provider(&xgene_msi_get_fwnode);
>>> >> +#endif
>>> >>       return 0;
>>> >>  }
>>> >>
>>> >> @@ -449,6 +460,13 @@ static int xgene_msi_hwirq_free(unsigned int cpu)
>>> >>       {},
>>> >>  };
>>> >>
>>> >> +#ifdef CONFIG_ACPI
>>> >> +static const struct acpi_device_id xgene_msi_acpi_ids[] = {
>>> >> +     {"APMC0D0E", 0},
>>> >> +     { },
>>> >> +};
>>> >> +#endif
>>> >> +
>>> >>  static int xgene_msi_probe(struct platform_device *pdev)
>>> >>  {
>>> >>       struct resource *res;
>>> >> @@ -469,7 +487,17 @@ static int xgene_msi_probe(struct platform_device *pdev)
>>> >>               goto error;
>>> >>       }
>>> >>       xgene_msi->msi_addr = res->start;
>>> >> -     xgene_msi->node = pdev->dev.of_node;
>>> >> +
>>> >> +     xgene_msi->fwnode = of_node_to_fwnode(pdev->dev.of_node);
>>> >> +     if (!xgene_msi->fwnode) {
>>> >> +             xgene_msi->fwnode = irq_domain_alloc_fwnode(NULL);
>>> >
>>> > Please provide something other than NULL, such as the base address if
>>> > the device. That's quite useful for debugging.
>>> >
>>> >> +             if (!xgene_msi->fwnode) {
>>> >> +                     dev_err(&pdev->dev, "Failed to create fwnode\n");
>>> >> +                     rc = ENOMEM;
>>> >> +                     goto error;
>>> >> +             }
>>> >> +     }
>>> >> +
>>> >>       xgene_msi->num_cpus = num_possible_cpus();
>>> >>
>>> >>       rc = xgene_msi_init_allocator(xgene_msi);
>>> >> @@ -540,6 +568,7 @@ static int xgene_msi_probe(struct platform_device *pdev)
>>> >>       .driver = {
>>> >>               .name = "xgene-msi",
>>> >>               .of_match_table = xgene_msi_match_table,
>>> >> +             .acpi_match_table = ACPI_PTR(xgene_msi_acpi_ids),
>>> >>       },
>>> >>       .probe = xgene_msi_probe,
>>> >>       .remove = xgene_msi_remove,
>>> >>
>>> >
>>> > The code is trivial, but relies on the MSI controller to probe before
>>> > the PCI bus. What enforces this? How is it making sure that this is not
>>> > going to break in the next kernel release? As far as I can tell, there
>>> > is no explicit dependency between the two, making it the whole thing
>>> > extremely fragile.
>>> >
>>> > Thanks,
>>> >
>>> >         M.
>>> > --
>>> > Jazz is not dead. It just smells funny...
>>>
>>> --