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

Secondly, I commented on this before, so you know what my opinion is.

Finally, please execute this command on the vmlinux that "works"
for you:

nm vmlinux | grep -E '__initcall_(xgene_pcie_msi_init|acpi_init)'

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@arm.com> wrote:
> > On 28/04/17 01:54, Khuong Dinh wrote:
> >> From: Khuong Dinh <kdinh@apm.com>
> >>
> >> 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@apm.com>
> >> Signed-off-by: Duc Dang <dhdang@apm.com>
> >> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> >> ---
> >> 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...
>
> --
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