Re: [PATCH V7 07/11] pci, acpi: Handle ACPI companion assignment.

[Jayachandran C <jchandra@broadcom.com>]

On Thu, May 12, 2016 at 4:13 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Wed, May 11, 2016 at 10:30:51PM +0200, Rafael J. Wysocki wrote:
>> On Wed, May 11, 2016 at 12:11 PM, Lorenzo Pieralisi
>> <lorenzo.pieralisi@arm.com> wrote:
>> > On Tue, May 10, 2016 at 08:37:00PM +0200, Rafael J. Wysocki wrote:
>> >> On Tue, May 10, 2016 at 5:19 PM, Tomasz Nowicki <tn@semihalf.com> wrote:
>> >> > This patch provides a way to set the ACPI companion in PCI code.
>> >> > We define acpi_pci_set_companion() to set the ACPI companion pointer and
>> >> > call it from PCI core code. The function is stub for now.
>> >> >
>> >> > Signed-off-by: Jayachandran C <jchandra@broadcom.com>
>> >> > Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
>> >> > ---
>> >> >  drivers/pci/probe.c      | 2 ++
>> >> >  include/linux/pci-acpi.h | 4 ++++
>> >> >  2 files changed, 6 insertions(+)
>> >> >
>> >> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> >> > index 8004f67..fb0b752 100644
>> >> > --- a/drivers/pci/probe.c
>> >> > +++ b/drivers/pci/probe.c
>> >> > @@ -12,6 +12,7 @@
>> >> >  #include <linux/slab.h>
>> >> >  #include <linux/module.h>
>> >> >  #include <linux/cpumask.h>
>> >> > +#include <linux/pci-acpi.h>
>> >> >  #include <linux/pci-aspm.h>
>> >> >  #include <linux/aer.h>
>> >> >  #include <linux/acpi.h>
>> >> > @@ -2141,6 +2142,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>> >> >         bridge->dev.parent = parent;
>> >> >         bridge->dev.release = pci_release_host_bridge_dev;
>> >> >         dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
>> >> > +       acpi_pci_set_companion(bridge);
>> >>
>> >> Yes, we'll probably add something similar here.
>> >>
>> >> Do I think now is the right time to do that?  No.
>> >>
>> >> >         error = pcibios_root_bridge_prepare(bridge);
>> >> >         if (error) {
>> >> >                 kfree(bridge);
>> >> > diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
>> >> > index 09f9f02..1baa515 100644
>> >> > --- a/include/linux/pci-acpi.h
>> >> > +++ b/include/linux/pci-acpi.h
>> >> > @@ -111,6 +111,10 @@ static inline void acpi_pci_add_bus(struct pci_bus *bus) { }
>> >> >  static inline void acpi_pci_remove_bus(struct pci_bus *bus) { }
>> >> >  #endif /* CONFIG_ACPI */
>> >> >
>> >> > +static inline void acpi_pci_set_companion(struct pci_host_bridge *bridge)
>> >> > +{
>> >> > +}
>> >> > +
>> >> >  static inline int acpi_pci_bus_domain_nr(struct pci_bus *bus)
>> >> >  {
>> >> >         return 0;
>> >> > --
>> >>
>> >> Honestly, to me it looks like this series is trying very hard to avoid
>> >> doing any PCI host bridge configuration stuff from arch/arm64/
>> >> although (a) that might be simpler and (b) it would allow us to
>> >> identify the code that's common between *all* architectures using ACPI
>> >> support for host bridge configuration and to move *that* to a common
>> >> place later.  As done here it seems to be following the "ARM64 is
>> >> generic and the rest of the world is special" line which isn't really
>> >> helpful.
>> >
>> > I think patch [1-2] should be merged regardless (they may require minor
>> > tweaks if we decide to move pci_acpi_scan_root() to arch/arm64 though,
>> > for include files location). I guess you are referring to patch 8 in
>> > your comments above, which boils down to deciding whether:
>> >
>> > - pci_acpi_scan_root() (and unfortunately all the MCFG/ECAM handling that
>> >   goes with it) should live in arch/arm64 or drivers/acpi
>>
>> To be precise, everything under #ifdef CONFIG_ACPI_PCI_HOST_GENERIC or
>> equivalent is de facto ARM64-specific, because (as it stands in the
>> patch series) ARM64 is the only architecture that will select that
>> option.  Unless you are aware of any more architectures planning to
>> use ACPI (and I'm not aware of any), it will stay the only
>> architecture selecting it in the foreseeable future.
>>
>> Therefore you could replace CONFIG_ACPI_PCI_HOST_GENERIC with
>> CONFIG_ARM64 everywhere in that code which is why in my opinion the
>> code should live somewhere under arch/arm64/.
>>
>> Going forward, it should be possible to identify common parts of the
>> PCI host bridge configuration code in arch/ and move it to
>> drivers/acpi/ or drivers/pci/, but I bet that won't be the entire code
>> this series puts under CONFIG_ACPI_PCI_HOST_GENERIC.
>>
>> The above leads to a quite straightforward conclusion about the order
>> in which to do things: I'd add ACPI support for PCI host bridge on
>> ARM64 following what's been done on ia64 (as x86 is more quirky and
>> kludgy overall) as far as reasonably possible first and then think
>> about moving common stuff to a common place.
>
> That does seem like a reasonable approach.  I had hoped to get more of
> this in for v4.7, but we don't have much time left.  Maybe some of
> Rafael's comments can be addressed by moving and slight restructuring
> and we can still squeeze it in.
>
> The first three patches:
>
>   PCI: Provide common functions for ECAM mapping
>   PCI: generic, thunder: Use generic ECAM API
>   PCI, of: Move PCI I/O space management to PCI core code
>
> seem relatively straightforward, and I applied them to pci/arm64 with
> the intent of merging them unless there are objections.  I made the
> following tweaks, mainly to try to improve some error messages:
>
> diff --git a/drivers/pci/ecam.c b/drivers/pci/ecam.c
> index 3d52005..e1add01 100644
> --- a/drivers/pci/ecam.c
> +++ b/drivers/pci/ecam.c
> @@ -24,9 +24,9 @@
>  #include "ecam.h"
>
>  /*
> - * On 64 bit systems, we do a single ioremap for the whole config space
> - * since we have enough virtual address range available. On 32 bit, do an
> - * ioremap per bus.
> + * On 64-bit systems, we do a single ioremap for the whole config space
> + * since we have enough virtual address range available.  On 32-bit, we
> + * ioremap the config space for each bus individually.
>   */
>  static const bool per_bus_mapping = !config_enabled(CONFIG_64BIT);
>
> @@ -42,6 +42,7 @@ struct pci_config_window *pci_ecam_create(struct device *dev,
>  {
>         struct pci_config_window *cfg;
>         unsigned int bus_range, bus_range_max, bsz;
> +       struct resource *conflict;
>         int i, err;
>
>         if (busr->start > busr->end)
> @@ -58,10 +59,10 @@ struct pci_config_window *pci_ecam_create(struct device *dev,
>         bus_range = resource_size(&cfg->busr);
>         bus_range_max = resource_size(cfgres) >> ops->bus_shift;
>         if (bus_range > bus_range_max) {
> -               dev_warn(dev, "bus max %#x reduced to %#x",
> -                                       bus_range, bus_range_max);
>                 bus_range = bus_range_max;
>                 cfg->busr.end = busr->start + bus_range - 1;
> +               dev_warn(dev, "ECAM area %pR can only accommodate %pR (reduced from %pR desired)\n",
> +                        cfgres, &cfg->busr, busr);
>         }
>         bsz = 1 << ops->bus_shift;
>
> @@ -70,9 +71,11 @@ struct pci_config_window *pci_ecam_create(struct device *dev,
>         cfg->res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
>         cfg->res.name = "PCI ECAM";
>
> -       err = request_resource(&iomem_resource, &cfg->res);
> -       if (err) {
> -               dev_err(dev, "request ECAM res %pR failed\n", &cfg->res);
> +       conflict = request_resource(&iomem_resource, &cfg->res);
> +       if (conflict) {
> +               err = -EBUSY;
> +               dev_err(dev, "can't claim ECAM area %pR: address conflict with %s %pR\n",
> +                       &cfg->res, conflict->name, conflict);
>                 goto err_exit;
>         }
>
> diff --git a/drivers/pci/ecam.h b/drivers/pci/ecam.h
> index 1ad2176..9878beb 100644
> --- a/drivers/pci/ecam.h
> +++ b/drivers/pci/ecam.h
> @@ -33,7 +33,7 @@ struct pci_ecam_ops {
>
>  /*
>   * struct to hold the mappings of a config space window. This
> - * is expected to be used as sysdata for PCI controlllers which
> + * is expected to be used as sysdata for PCI controllers that
>   * use ECAM.
>   */
>  struct pci_config_window {
> @@ -43,11 +43,11 @@ struct pci_config_window {
>         struct pci_ecam_ops             *ops;
>         union {
>                 void __iomem            *win;   /* 64-bit single mapping */
> -               void __iomem            **winp; /* 32-bit per bus mapping */
> +               void __iomem            **winp; /* 32-bit per-bus mapping */
>         };
>  };
>
> -/* create and free for pci_config_window */
> +/* create and free pci_config_window */
>  struct pci_config_window *pci_ecam_create(struct device *dev,
>                 struct resource *cfgres, struct resource *busr,
>                 struct pci_ecam_ops *ops);
> @@ -56,11 +56,11 @@ void pci_ecam_free(struct pci_config_window *cfg);
>  /* map_bus when ->sysdata is an instance of pci_config_window */
>  void __iomem *pci_ecam_map_bus(struct pci_bus *bus, unsigned int devfn,
>                                int where);
> -/* default ECAM ops, bus shift 20, generic read and write */
> +/* default ECAM ops */
>  extern struct pci_ecam_ops pci_generic_ecam_ops;
>
>  #ifdef CONFIG_PCI_HOST_GENERIC
> -/* for DT based pci controllers that support ECAM */
> +/* for DT-based PCI controllers that support ECAM */
>  int pci_host_common_probe(struct platform_device *pdev,
>                           struct pci_ecam_ops *ops);
>  #endif

If we are moving the ACPI/PCI code from drivers/acpi to
arch/arm64/ , there is an issue in having the header file
ecam.h in drivers/pci

The current include of "../pci/ecam.h" is slightly ugly (Arnd
and David had already noted this), but including the driver
header from arch code would be even worse.

I can either merge ecam.h into include/linux/pci.h
or move it to a new file include/linux/pci-ecam.h, any
suggestion on which is preferable?

JC.