[V4,17/23] acpi, mcfg: Add default PCI config accessors implementation and initial support for related quirks.

We use generic accessors from access.c by default. However, we already
know platforms that need special handling while accessing to PCI config
space. These platforms will need different accessors set matched against
platform ID, domain, bus touple. Therefore we are going to add (in future)
DECLARE_ACPI_MCFG_FIXUP which will register platform specific custom
accessors. For now, we let pci_mcfg_get_ops to take acpi_pci_root structure
as an arguments and left some space for quirk matching algorithm.

Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Tested-by: Duc Dang <dhdang@apm.com>
Tested-by: Dongdong Liu <liudongdong3@huawei.com>
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Graeme Gregory <graeme.gregory@linaro.org>
Tested-by: Sinan Kaya <okaya@codeaurora.org>
---
 drivers/acpi/mcfg.c      | 30 ++++++++++++++++++++++++++++++
 include/linux/pci-acpi.h |  8 ++++++++
 2 files changed, 38 insertions(+)

On Thu, Feb 4, 2016 at 10:58 PM, Tomasz Nowicki <tn@semihalf.com> wrote:
> We use generic accessors from access.c by default. However, we already
> know platforms that need special handling while accessing to PCI config
> space. These platforms will need different accessors set matched against
> platform ID, domain, bus touple. Therefore we are going to add (in future)
> DECLARE_ACPI_MCFG_FIXUP which will register platform specific custom
> accessors. For now, we let pci_mcfg_get_ops to take acpi_pci_root structure
> as an arguments and left some space for quirk matching algorithm.
>
> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> Tested-by: Duc Dang <dhdang@apm.com>
> Tested-by: Dongdong Liu <liudongdong3@huawei.com>
> Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
> Tested-by: Graeme Gregory <graeme.gregory@linaro.org>
> Tested-by: Sinan Kaya <okaya@codeaurora.org>
> ---
>  drivers/acpi/mcfg.c      | 30 ++++++++++++++++++++++++++++++
>  include/linux/pci-acpi.h |  8 ++++++++
>  2 files changed, 38 insertions(+)
>
> diff --git a/drivers/acpi/mcfg.c b/drivers/acpi/mcfg.c
> index dca4c4e..dfc2d14 100644
> --- a/drivers/acpi/mcfg.c
> +++ b/drivers/acpi/mcfg.c
> @@ -34,6 +34,36 @@ int __weak raw_pci_write(unsigned int domain, unsigned int bus,
>         return PCIBIOS_DEVICE_NOT_FOUND;
>  }
>
> +void __iomem *
> +pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset)
> +{
> +       struct pci_mmcfg_region *cfg;
> +
> +       cfg = pci_mmconfig_lookup(pci_domain_nr(bus), bus->number);

In the existing code, calls to pci_mmconfig_lookup() is done inside an
rcu_read_lock/rcu_read_unlock pair. Any reason that is not required here?

Also, you can avoid having to do the lookup every time by saving a cfg pointer
see http://lists.infradead.org/pipermail/linux-arm-kernel/2016-January/396921.html


> +       if (cfg && cfg->virt)
> +               return cfg->virt +
> +                       (PCI_MMCFG_BUS_OFFSET(bus->number) | (devfn << 12)) +
> +                       offset;

PCI_MMCFG_OFFSET(bus->number, devfn) would be better

> +       return NULL;
> +}
> +
> +/* Default generic PCI config accessors */
> +static struct pci_ops default_pci_mcfg_ops = {
> +       .map_bus = pci_mcfg_dev_base,
> +       .read = pci_generic_config_read,
> +       .write = pci_generic_config_write,
> +};
> +
> +struct pci_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
> +{
> +       /*
> +        * TODO: Match against platform specific quirks and return
> +        * corresponding PCI config space accessor set.
> +        */
> +
> +       return &default_pci_mcfg_ops;
> +}

Is it necessary to make these non-static, even in the next patch, the
functions are only used from this file.

> +
>  int __init acpi_parse_mcfg(struct acpi_table_header *header)
>  {
>         struct acpi_table_mcfg *mcfg;
> diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
> index 65b91f3..c974586 100644
> --- a/include/linux/pci-acpi.h
> +++ b/include/linux/pci-acpi.h
> @@ -83,10 +83,18 @@ void acpi_pci_remove_bus(struct pci_bus *bus);
>  #ifdef CONFIG_PCI_MMCONFIG
>  int pci_mmcfg_setup_map(struct acpi_pci_root_info *ci);
>  void pci_mmcfg_teardown_map(struct acpi_pci_root_info *ci);
> +struct pci_ops *pci_mcfg_get_ops(struct acpi_pci_root *root);
> +void __iomem *
> +pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset);
>  #else
>  static inline int pci_mmcfg_setup_map(struct acpi_pci_root_info *ci)
>  { return 0; }
>  static inline void pci_mmcfg_teardown_map(struct acpi_pci_root_info *ci) { }
> +static inline struct pci_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
> +{ return NULL; }
> +static inline void __iomem *
> +pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset)
> +{ return NULL; }
>  #endif
>  #ifdef CONFIG_ACPI_PCI_SLOT

JC.
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On Mon, Feb 29, 2016 at 01:33:41PM +0530, Jayachandran Chandrashekaran Nair wrote:
> On Thu, Feb 4, 2016 at 10:58 PM, Tomasz Nowicki <tn@semihalf.com> wrote:
> > We use generic accessors from access.c by default. However, we already
> > know platforms that need special handling while accessing to PCI config
> > space. These platforms will need different accessors set matched against
> > platform ID, domain, bus touple. Therefore we are going to add (in future)
> > DECLARE_ACPI_MCFG_FIXUP which will register platform specific custom
> > accessors. For now, we let pci_mcfg_get_ops to take acpi_pci_root structure
> > as an arguments and left some space for quirk matching algorithm.
> >
> > Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> > Tested-by: Duc Dang <dhdang@apm.com>
> > Tested-by: Dongdong Liu <liudongdong3@huawei.com>
> > Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
> > Tested-by: Graeme Gregory <graeme.gregory@linaro.org>
> > Tested-by: Sinan Kaya <okaya@codeaurora.org>
> > ---
> >  drivers/acpi/mcfg.c      | 30 ++++++++++++++++++++++++++++++
> >  include/linux/pci-acpi.h |  8 ++++++++
> >  2 files changed, 38 insertions(+)
> >
> > diff --git a/drivers/acpi/mcfg.c b/drivers/acpi/mcfg.c
> > index dca4c4e..dfc2d14 100644
> > --- a/drivers/acpi/mcfg.c
> > +++ b/drivers/acpi/mcfg.c
> > @@ -34,6 +34,36 @@ int __weak raw_pci_write(unsigned int domain, unsigned int bus,
> >         return PCIBIOS_DEVICE_NOT_FOUND;
> >  }
> >
> > +void __iomem *
> > +pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset)
> > +{
> > +       struct pci_mmcfg_region *cfg;
> > +
> > +       cfg = pci_mmconfig_lookup(pci_domain_nr(bus), bus->number);
> 
> In the existing code, calls to pci_mmconfig_lookup() is done inside an
> rcu_read_lock/rcu_read_unlock pair. Any reason that is not required here?
> 
> Also, you can avoid having to do the lookup every time by saving a cfg pointer
> see http://lists.infradead.org/pipermail/linux-arm-kernel/2016-January/396921.html

Yes, this is much better (and sysdata usage is self-contained, it does
not trickle into other bits of the kernel - ie arch code), it should be
integrated in the final version of the patchset.

> > +       if (cfg && cfg->virt)
> > +               return cfg->virt +
> > +                       (PCI_MMCFG_BUS_OFFSET(bus->number) | (devfn << 12)) +
> > +                       offset;
> 
> PCI_MMCFG_OFFSET(bus->number, devfn) would be better

Ditto.

Thanks,
Lorenzo

> 
> > +       return NULL;
> > +}
> > +
> > +/* Default generic PCI config accessors */
> > +static struct pci_ops default_pci_mcfg_ops = {
> > +       .map_bus = pci_mcfg_dev_base,
> > +       .read = pci_generic_config_read,
> > +       .write = pci_generic_config_write,
> > +};
> > +
> > +struct pci_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
> > +{
> > +       /*
> > +        * TODO: Match against platform specific quirks and return
> > +        * corresponding PCI config space accessor set.
> > +        */
> > +
> > +       return &default_pci_mcfg_ops;
> > +}
> 
> Is it necessary to make these non-static, even in the next patch, the
> functions are only used from this file.
> 
> > +
> >  int __init acpi_parse_mcfg(struct acpi_table_header *header)
> >  {
> >         struct acpi_table_mcfg *mcfg;
> > diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
> > index 65b91f3..c974586 100644
> > --- a/include/linux/pci-acpi.h
> > +++ b/include/linux/pci-acpi.h
> > @@ -83,10 +83,18 @@ void acpi_pci_remove_bus(struct pci_bus *bus);
> >  #ifdef CONFIG_PCI_MMCONFIG
> >  int pci_mmcfg_setup_map(struct acpi_pci_root_info *ci);
> >  void pci_mmcfg_teardown_map(struct acpi_pci_root_info *ci);
> > +struct pci_ops *pci_mcfg_get_ops(struct acpi_pci_root *root);
> > +void __iomem *
> > +pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset);
> >  #else
> >  static inline int pci_mmcfg_setup_map(struct acpi_pci_root_info *ci)
> >  { return 0; }
> >  static inline void pci_mmcfg_teardown_map(struct acpi_pci_root_info *ci) { }
> > +static inline struct pci_ops *pci_mcfg_get_ops(struct acpi_pci_root *root)
> > +{ return NULL; }
> > +static inline void __iomem *
> > +pci_mcfg_dev_base(struct pci_bus *bus, unsigned int devfn, int offset)
> > +{ return NULL; }
> >  #endif
> >  #ifdef CONFIG_ACPI_PCI_SLOT
> 
> JC.
> 
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