Re: [Xen-devel] [PATCH v3 04/27] arm/MSI: Save MSI chip in pci_sys_data

[Bjorn Helgaas <bhelgaas@xxxxxxxxxx>]

On Wed, Oct 15, 2014 at 11:06:52AM +0800, Yijing Wang wrote:
> Saving msi chip in pci_sys_data can make pci bus and
> devices don't need to know msi chip detail, it also
> make pci enumeration code be decoupled from msi chip.
> In fact, all pci devices under the same pci hostbridge
> share same msi chip. So msi chip should be seen as one
> of resources or attributes to be initialized in pci host
> bridge driver. Currently, pci hostbridge drivers create
> pci_host_bridge in pci_create_root_bus(), and pass arch
> specific pci sysdata to core pci scan functions. So pci
> arch sysdata is good place to save msi chip.
> 
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> ---
>  arch/arm/include/asm/mach/pci.h |    6 ++++++
>  arch/arm/include/asm/pci.h      |    9 +++++++++
>  arch/arm/kernel/bios32.c        |    3 +++
>  drivers/pci/msi.c               |    6 ++++++
>  include/linux/pci.h             |    9 +++++++++
>  5 files changed, 33 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mach/pci.h b/arch/arm/include/asm/mach/pci.h
> index 7fc4278..59b0d87 100644
> --- a/arch/arm/include/asm/mach/pci.h
> +++ b/arch/arm/include/asm/mach/pci.h
> @@ -22,6 +22,9 @@ struct hw_pci {
>  #ifdef CONFIG_PCI_DOMAINS
>       int             domain;
>  #endif
> +#ifdef CONFIG_PCI_MSI
> +     struct msi_chip *msi_chip;
> +#endif
>       struct pci_ops  *ops;
>       int             nr_controllers;
>       void            **private_data;
> @@ -47,6 +50,9 @@ struct pci_sys_data {
>  #ifdef CONFIG_PCI_DOMAINS
>       int             domain;
>  #endif
> +#ifdef CONFIG_PCI_MSI
> +     struct msi_chip *msi_chip;
> +#endif
>       struct list_head node;
>       int             busnr;          /* primary bus number                   
> */
>       u64             mem_offset;     /* bus->cpu memory mapping offset       
> */
> diff --git a/arch/arm/include/asm/pci.h b/arch/arm/include/asm/pci.h
> index 7e95d85..b562c09 100644
> --- a/arch/arm/include/asm/pci.h
> +++ b/arch/arm/include/asm/pci.h
> @@ -31,6 +31,15 @@ static inline int pci_proc_domain(struct pci_bus *bus)
>  }
>  #endif /* CONFIG_PCI_DOMAINS */
>  
> +#ifdef CONFIG_PCI_MSI
> +static inline struct msi_chip *pci_msi_chip(struct pci_bus *bus)
> +{
> +     struct pci_sys_data *root = bus->sysdata;
> +
> +     return root->msi_chip;
> +}
> +#endif
> +
>  /*
>   * The PCI address space does equal the physical memory address space.
>   * The networking and block device layers use this boolean for bounce
> diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c
> index 17a26c1..a19038d 100644
> --- a/arch/arm/kernel/bios32.c
> +++ b/arch/arm/kernel/bios32.c
> @@ -471,6 +471,9 @@ static void pcibios_init_hw(struct device *parent, struct 
> hw_pci *hw,
>  #ifdef CONFIG_PCI_DOMAINS
>               sys->domain  = hw->domain;
>  #endif
> +#ifdef CONFIG_PCI_MSI
> +             sys->msi_chip = hw->msi_chip;
> +#endif
>               sys->busnr   = busnr;
>               sys->swizzle = hw->swizzle;
>               sys->map_irq = hw->map_irq;
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 22e413c..f11108c 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -35,6 +35,9 @@ int __weak arch_setup_msi_irq(struct pci_dev *dev, struct 
> msi_desc *desc)
>       struct msi_chip *chip = dev->bus->msi;
>       int err;
>  
> +     if (!chip)
> +             chip = pci_msi_chip(dev->bus);
> +
>       if (!chip || !chip->setup_irq)
>               return -EINVAL;
>  
> @@ -50,6 +53,9 @@ void __weak arch_teardown_msi_irq(unsigned int irq)
>       struct msi_desc *entry = irq_get_msi_desc(irq);
>       struct msi_chip *chip = entry->dev->bus->msi;
>  
> +     if (!chip)
> +             chip = pci_msi_chip(entry->dev->bus);
> +
>       if (!chip || !chip->teardown_irq)
>               return;
>  
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 9cd2721..7a48b40 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1433,6 +1433,15 @@ static inline int pci_get_new_domain_nr(void) { return 
> -ENOSYS; }
>  
>  #include <asm/pci.h>
>  
> +/* Just avoid compile error, will be clean up later */
> +#ifdef CONFIG_PCI_MSI
> +
> +#ifndef pci_msi_chip
> +#define pci_msi_chip(bus)    NULL
> +#endif
> +#endif

I don't like the mixture of ARM changes and PCI core changes in the same
patch.  Can you split this into a core patch that does something like this:

  struct msi_chip * __weak pcibios_msi_controller(struct pci_bus *bus)
  {
    return NULL;
  }

  struct msi_chip *pci_msi_controller(struct pci_bus *bus)
  {
    msi_chip *controller = bus->msi;

    if (controller)
      return controller;
    return pcibios_msi_controller(bus);
  }

followed by an ARM patch that puts the msi_chip pointer in struct hw_pci
and implements pcibios_msi_controller()?

I know you're trying to *remove* weak functions, and this adds one, but
this section of the series is more about getting rid of the ARM
pcibios_add_bus() because all it was used for was setting the bus->msi
pointer.

Eventually we might have a way to stash an MSI controller pointer in the
generic pci_host_bridge struct, and then the pcibios_msi_controller()
interface could go away.

> +
>  /* these helpers provide future and backwards compatibility
>   * for accessing popular PCI BAR info */
>  #define pci_resource_start(dev, bar) ((dev)->resource[(bar)].start)
> -- 
> 1.7.1
> 

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