Re: [PATCH v4 3/3] PCI: pciehp: Add dmi table for in-band presence disabled

[Andy Shevchenko]

On Fri, Oct 25, 2019 at 10:01 PM Stuart Hayes <stuart.w.hayes@xxxxxxxxx> wrote:
>
> Some systems have in-band presence detection disabled for hot-plug PCI
> slots, but do not report this in the slot capabilities 2 (SLTCAP2) register.
> On these systems, presence detect can become active well after the link is
> reported to be active, which can cause the slots to be disabled after a
> device is connected.
>
> Add a dmi table to flag these systems as having in-band presence disabled.
>

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

> Signed-off-by: Stuart Hayes <stuart.w.hayes@xxxxxxxxx>
> ---
> v4
>   add comment to dmi table
>
>  drivers/pci/hotplug/pciehp_hpc.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 02d95ab27a12..9541735bd0aa 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -14,6 +14,7 @@
>
>  #define dev_fmt(fmt) "pciehp: " fmt
>
> +#include <linux/dmi.h>
>  #include <linux/kernel.h>
>  #include <linux/types.h>
>  #include <linux/jiffies.h>
> @@ -26,6 +27,24 @@
>  #include "../pci.h"
>  #include "pciehp.h"
>
> +static const struct dmi_system_id inband_presence_disabled_dmi_table[] = {
> +       /*
> +        * Match all Dell systems, as some Dell systems have inband
> +        * presence disabled on NVMe slots (but don't support the bit to
> +        * report it). Setting inband presence disabled should have no
> +        * negative effect, except on broken hotplug slots that never
> +        * assert presence detect--and those will still work, they will
> +        * just have a bit of extra delay before being probed.
> +        */
> +       {
> +               .ident = "Dell System",
> +               .matches = {
> +                       DMI_MATCH(DMI_OEM_STRING, "Dell System"),
> +               },
> +       },
> +       {}
> +};
> +
>  static inline struct pci_dev *ctrl_dev(struct controller *ctrl)
>  {
>         return ctrl->pcie->port;
> @@ -895,6 +914,9 @@ struct controller *pcie_init(struct pcie_device *dev)
>                 ctrl->inband_presence_disabled = 1;
>         }
>
> +       if (dmi_first_match(inband_presence_disabled_dmi_table))
> +               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.
> --
> 2.18.1
>


-- 
With Best Regards,
Andy Shevchenko