Re: [PATCH v2] PCI: assign bus numbers present in EA capability for bridges

[sundeep subbaraya]

Hi Bjorn / Sean,

Any comments?

Thanks,
Sundeep

On Mon, Nov 19, 2018 at 6:44 PM <sundeep.lkml@xxxxxxxxx> wrote:
>
> From: Subbaraya Sundeep <sbhatta@xxxxxxxxxxx>
>
> As per the spec, bridges with EA capability work
> with fixed secondary and subordinate bus numbers.
> Hence assign bus numbers to bridges from EA if the
> capability exists.
>
> Signed-off-by: Subbaraya Sundeep <sbhatta@xxxxxxxxxxx>
> ---
> Changes for v2:
>         No changes just added Sean Stalley who did EA support for BARs.
>
>  drivers/pci/probe.c           | 58 ++++++++++++++++++++++++++++++++++++++++---
>  include/uapi/linux/pci_regs.h |  6 +++++
>  2 files changed, 60 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index b1c05b5..f41d2e6 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1030,6 +1030,40 @@ static void pci_enable_crs(struct pci_dev *pdev)
>
>  static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
>                                               unsigned int available_buses);
> +/*
> + * pci_ea_fixed_busnrs() - Read fixed Secondary and Subordinate bus
> + * numbers from EA capability.
> + * @dev: Bridge with EA
> + * @secondary: updated with secondary bus number in EA
> + * @subordinate: updated with subordinate bus number in EA
> + *
> + * If it is a bridge with EA capability then fixed bus numbers are
> + * read from EA capability list and secondary, subordinate reference
> + * variables will be updated. Otherwise secondary and subordinate reference
> + * variables will be zeroed.
> + */
> +static void pci_ea_fixed_busnrs(struct pci_dev *dev, u8 *secondary,
> +                               u8 *subordinate)
> +{
> +       int ea;
> +       int offset;
> +       u32 dw;
> +
> +       *secondary = *subordinate = 0;
> +
> +       if (dev->hdr_type != PCI_HEADER_TYPE_BRIDGE)
> +               return;
> +
> +       /* find PCI EA capability in list */
> +       ea = pci_find_capability(dev, PCI_CAP_ID_EA);
> +       if (!ea)
> +               return;
> +
> +       offset = ea + PCI_EA_FIRST_ENT;
> +       pci_read_config_dword(dev, offset, &dw);
> +       *secondary =  dw & PCI_EA_SEC_BUS_MASK;
> +       *subordinate = (dw & PCI_EA_SUB_BUS_MASK) >> PCI_EA_SUB_BUS_SHIFT;
> +}
>
>  /*
>   * pci_scan_bridge_extend() - Scan buses behind a bridge
> @@ -1064,6 +1098,8 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
>         u16 bctl;
>         u8 primary, secondary, subordinate;
>         int broken = 0;
> +       u8 fixed_sec, fixed_sub;
> +       int next_busnr;
>
>         /*
>          * Make sure the bridge is powered on to be able to access config
> @@ -1163,17 +1199,25 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
>                 /* Clear errors */
>                 pci_write_config_word(dev, PCI_STATUS, 0xffff);
>
> +               /* read bus numbers from EA */
> +               pci_ea_fixed_busnrs(dev, &fixed_sec, &fixed_sub);
> +
> +               next_busnr = max + 1;
> +               /* Use secondary bus number in EA */
> +               if (fixed_sec)
> +                       next_busnr = fixed_sec;
> +
>                 /*
>                  * Prevent assigning a bus number that already exists.
>                  * This can happen when a bridge is hot-plugged, so in this
>                  * case we only re-scan this bus.
>                  */
> -               child = pci_find_bus(pci_domain_nr(bus), max+1);
> +               child = pci_find_bus(pci_domain_nr(bus), next_busnr);
>                 if (!child) {
> -                       child = pci_add_new_bus(bus, dev, max+1);
> +                       child = pci_add_new_bus(bus, dev, next_busnr);
>                         if (!child)
>                                 goto out;
> -                       pci_bus_insert_busn_res(child, max+1,
> +                       pci_bus_insert_busn_res(child, next_busnr,
>                                                 bus->busn_res.end);
>                 }
>                 max++;
> @@ -1234,7 +1278,13 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
>                         max += i;
>                 }
>
> -               /* Set subordinate bus number to its real value */
> +               /*
> +                * Set subordinate bus number to its real value.
> +                * If fixed subordinate bus number exists from EA
> +                * capability then use it.
> +                */
> +               if (fixed_sub)
> +                       max = fixed_sub;
>                 pci_bus_update_busn_res_end(child, max);
>                 pci_write_config_byte(dev, PCI_SUBORDINATE_BUS, max);
>         }
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index e1e9888..c3d0904 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -372,6 +372,12 @@
>  #define PCI_EA_FIRST_ENT_BRIDGE        8       /* First EA Entry for Bridges */
>  #define  PCI_EA_ES             0x00000007 /* Entry Size */
>  #define  PCI_EA_BEI            0x000000f0 /* BAR Equivalent Indicator */
> +
> +/* EA fixed Secondary and Subordinate bus numbers for Bridge */
> +#define PCI_EA_SEC_BUS_MASK    0xff
> +#define PCI_EA_SUB_BUS_MASK    0xff00
> +#define PCI_EA_SUB_BUS_SHIFT   8
> +
>  /* 0-5 map to BARs 0-5 respectively */
>  #define   PCI_EA_BEI_BAR0              0
>  #define   PCI_EA_BEI_BAR5              5
> --
> 1.8.3.1
>