Re: [PATCH v4 1/3] PCI: pciehp: Add support for disabling in-band presence

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Fri, Oct 25, 2019 at 10:00 PM Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
>
> From: Alexandru Gagniuc <mr.nuke.me@gmail.com>
>
> The presence detect state (PDS) is normally a logical or of in-band and
> out-of-band presence. As of PCIe 4.0, there is the option to disable
> in-band presence so that the PDS bit always reflects the state of the
> out-of-band presence.
>
> The recommendation of the PCIe spec is to disable in-band presence
> whenever supported.
>

FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
> ---
>  drivers/pci/hotplug/pciehp.h     | 1 +
>  drivers/pci/hotplug/pciehp_hpc.c | 9 ++++++++-
>  include/uapi/linux/pci_regs.h    | 2 ++
>  3 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
> index 654c972b8ea0..27e4cd6529b0 100644
> --- a/drivers/pci/hotplug/pciehp.h
> +++ b/drivers/pci/hotplug/pciehp.h
> @@ -83,6 +83,7 @@ struct controller {
>         struct pcie_device *pcie;
>
>         u32 slot_cap;                           /* capabilities and quirks */
> +       unsigned int inband_presence_disabled:1;
>
>         u16 slot_ctrl;                          /* control register access */
>         struct mutex ctrl_lock;
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 1a522c1c4177..dc109d521f30 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -811,7 +811,7 @@ static inline void dbg_ctrl(struct controller *ctrl)
>  struct controller *pcie_init(struct pcie_device *dev)
>  {
>         struct controller *ctrl;
> -       u32 slot_cap, link_cap;
> +       u32 slot_cap, slot_cap2, link_cap;
>         u8 poweron;
>         struct pci_dev *pdev = dev->port;
>         struct pci_bus *subordinate = pdev->subordinate;
> @@ -869,6 +869,13 @@ struct controller *pcie_init(struct pcie_device *dev)
>                 FLAG(link_cap, PCI_EXP_LNKCAP_DLLLARC),
>                 pdev->broken_cmd_compl ? " (with Cmd Compl erratum)" : "");
>
> +       pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP2, &slot_cap2);
> +       if (slot_cap2 & PCI_EXP_SLTCAP2_IBPD) {
> +               pcie_write_cmd_nowait(ctrl, PCI_EXP_SLTCTL_IBPD_DISABLE,
> +                                     PCI_EXP_SLTCTL_IBPD_DISABLE);
> +               ctrl->inband_presence_disabled = 1;
> +       }
> +
>         /*
>          * If empty slot's power status is on, turn power off.  The IRQ isn't
>          * requested yet, so avoid triggering a notification with this command.
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 29d6e93fd15e..ea1cf9546e4d 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -604,6 +604,7 @@
>  #define  PCI_EXP_SLTCTL_PWR_OFF        0x0400 /* Power Off */
>  #define  PCI_EXP_SLTCTL_EIC    0x0800  /* Electromechanical Interlock Control */
>  #define  PCI_EXP_SLTCTL_DLLSCE 0x1000  /* Data Link Layer State Changed Enable */
> +#define  PCI_EXP_SLTCTL_IBPD_DISABLE   0x4000 /* In-band PD disable */
>  #define PCI_EXP_SLTSTA         26      /* Slot Status */
>  #define  PCI_EXP_SLTSTA_ABP    0x0001  /* Attention Button Pressed */
>  #define  PCI_EXP_SLTSTA_PFD    0x0002  /* Power Fault Detected */
> @@ -676,6 +677,7 @@
>  #define PCI_EXP_LNKSTA2                50      /* Link Status 2 */
>  #define PCI_CAP_EXP_ENDPOINT_SIZEOF_V2 52      /* v2 endpoints with link end here */
>  #define PCI_EXP_SLTCAP2                52      /* Slot Capabilities 2 */
> +#define  PCI_EXP_SLTCAP2_IBPD  0x0001  /* In-band PD Disable Supported */
>  #define PCI_EXP_SLTCTL2                56      /* Slot Control 2 */
>  #define PCI_EXP_SLTSTA2                58      /* Slot Status 2 */
>
> --
> 2.18.1
>


-- 
With Best Regards,
Andy Shevchenko