Subject: Re: [PATCH v2 1/4] pci/msi: Move "no_64bit_msi" flag from powerpc to generic pci_dev

From: Bjorn Helgaas <[email-masked]>
Date: Thu, 2 Oct 2014 09:31:01 -0600

On Thu, Oct 02, 2014 at 10:34:12AM +1000, Benjamin Herrenschmidt wrote:
> 
> Some devices have broken 64-bit MSI support which only support some
> address bits (40 to 48 typically). This doesn't work on some platforms
> such as POWER servers, so we need a quirk.
> 
> Currently we keep a flag in a powerpc specific data structure which we
> have per PCI device. However this is impractical as we really want the
> driver to set that flag appropriately (and the driver shouldn't touch
> that arch specific data structure).
> 
> It's also not unlikely that this limitation will affect other architectures
> in the long run.
> 
> So this moves the flag to struct pci_dev instead and adjusts the
> corresponding arch/powerpc code to look for it there. At this point,
> there is no attempt at making other architectures honor it just yet,
> though it appears that x86 doesn't care and always generates 32-bit
> MSI addresses.

I thought you were going to add something in drivers/pci to make this more
generic?

Is it feasible to structure this series as follows?

  - add generic stuff (struct pci_dev bit, msi.c checks)
  - add quirks to drivers to set the pci_dev bit
  - change powerpc to check pci_dev bit instead of pdn bit
  - remove powerpc-specific quirks since nobody looks as the pdn bit

I think it would be easier to follow if the powerpc-specific parts weren't
intertwined with the rest.

> Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
> CC: <[email-masked]>
> ---
> 
> v2: Rename flag to "no_64bit_msi" as suggested by Bjorn
> 
>  arch/powerpc/include/asm/pci-bridge.h     | 2 --
>  arch/powerpc/kernel/pci_64.c              | 5 +----
>  arch/powerpc/platforms/powernv/pci-ioda.c | 3 +--
>  arch/powerpc/platforms/powernv/pci.c      | 3 +--
>  arch/powerpc/platforms/pseries/msi.c      | 2 +-
>  include/linux/pci.h                       | 1 +
>  6 files changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
> index 4ca90a3..725247b 100644
> --- a/arch/powerpc/include/asm/pci-bridge.h
> +++ b/arch/powerpc/include/asm/pci-bridge.h
> @@ -159,8 +159,6 @@ struct pci_dn {
>  
>  	int	pci_ext_config_space;	/* for pci devices */
>  
> -	bool	force_32bit_msi;
> -
>  	struct	pci_dev *pcidev;	/* back-pointer to the pci device */
>  #ifdef CONFIG_EEH
>  	struct eeh_dev *edev;		/* eeh device */
> diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
> index 155013d..d41a831 100644
> --- a/arch/powerpc/kernel/pci_64.c
> +++ b/arch/powerpc/kernel/pci_64.c
> @@ -269,10 +269,7 @@ EXPORT_SYMBOL(pcibus_to_node);
>  
>  static void quirk_radeon_32bit_msi(struct pci_dev *dev)
>  {
> -	struct pci_dn *pdn = pci_get_pdn(dev);
> -
> -	if (pdn)
> -		pdn->force_32bit_msi = true;
> +	dev->no_64bit_msi = true;
>  }
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x68f2, quirk_radeon_32bit_msi);
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0xaa68, quirk_radeon_32bit_msi);
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index df241b1..a188bb8 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1311,7 +1311,6 @@ static int pnv_pci_ioda_msi_setup(struct pnv_phb *phb, struct pci_dev *dev,
>  				  unsigned int is_64, struct msi_msg *msg)
>  {
>  	struct pnv_ioda_pe *pe = pnv_ioda_get_pe(dev);
> -	struct pci_dn *pdn = pci_get_pdn(dev);
>  	struct irq_data *idata;
>  	struct irq_chip *ichip;
>  	unsigned int xive_num = hwirq - phb->msi_base;
> @@ -1327,7 +1326,7 @@ static int pnv_pci_ioda_msi_setup(struct pnv_phb *phb, struct pci_dev *dev,
>  		return -ENXIO;
>  
>  	/* Force 32-bit MSI on some broken devices */
> -	if (pdn && pdn->force_32bit_msi)
> +	if (dev->no_64bit_msi)
>  		is_64 = 0;
>  
>  	/* Assign XIVE to PE */
> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> index b854b57..89c6608 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -50,9 +50,8 @@ static int pnv_msi_check_device(struct pci_dev* pdev, int nvec, int type)
>  {
>  	struct pci_controller *hose = pci_bus_to_host(pdev->bus);
>  	struct pnv_phb *phb = hose->private_data;
> -	struct pci_dn *pdn = pci_get_pdn(pdev);
>  
> -	if (pdn && pdn->force_32bit_msi && !phb->msi32_support)
> +	if (pdev->no_64bit_msi && !phb->msi32_support)
>  		return -ENODEV;
>  
>  	return (phb && phb->msi_bmp.bitmap) ? 0 : -ENODEV;
> diff --git a/arch/powerpc/platforms/pseries/msi.c b/arch/powerpc/platforms/pseries/msi.c
> index 18ff462..6fd96d8 100644
> --- a/arch/powerpc/platforms/pseries/msi.c
> +++ b/arch/powerpc/platforms/pseries/msi.c
> @@ -429,7 +429,7 @@ static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec_in, int type)
>  	 */
>  again:
>  	if (type == PCI_CAP_ID_MSI) {
> -		if (pdn->force_32bit_msi) {
> +		if (pdev->no_64bit_msi) {
>  			rc = rtas_change_msi(pdn, RTAS_CHANGE_32MSI_FN, nvec);
>  			if (rc < 0) {
>  				/*
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 96453f9..fc938003 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -331,6 +331,7 @@ struct pci_dev {
>  	unsigned int	is_added:1;
>  	unsigned int	is_busmaster:1; /* device is busmaster */
>  	unsigned int	no_msi:1;	/* device may not use msi */
> +	unsigned int    no_64bit_msi:1;	/* Device has broken 64-bit MSIs */
>  	unsigned int	block_cfg_access:1;	/* config space access is blocked */
>  	unsigned int	broken_parity_status:1;	/* Device generates false positive parity */
>  	unsigned int	irq_reroute_variant:2;	/* device needs IRQ rerouting variant */
> 
> 
>