linux-kernel - Re: [PATCH 4/6] PCI: acpiphp: check for new devices on enabled host

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Date:	Tue, 25 Jun 2013 21:04:31 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Yinghai Lu <yinghai@...nel.org>, john.ronciak@...el.com,
	miles.j.penner@...el.com, bruce.w.allan@...el.com,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 4/6] PCI: acpiphp: check for new devices on enabled host

On Tue, Jun 25, 2013 at 7:22 PM, Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:

> Current acpiphp_check_bridge() implementation is pretty dumb:
>  - it enables the slot if it's not enabled and the slot status is
>    ACPI_STA_ALL;
>  - it disables the slot if it's enabled and slot is not in ACPI_STA_ALL
>    state.
>
> This behavior is not enough to handle Thunderbolt chaining case
> properly. We need to actually rescan for new devices even if a device
> has already in the slot.
>
> The new implementation disables and stops the slot if it's not in
> ACPI_STA_ALL state.
>
> For ACPI_STA_ALL state we first trim devices which don't respond and
> look for the ones after that. We do that even if slot already enabled
> (SLOT_ENABLED).

Just a couple of nitpicks below.

>         list_for_each_entry(slot, &bridge->slots, node) {
> +               struct pci_bus *bus = slot->bridge->pci_bus;
> +               struct pci_dev *dev, *tmp;
> +               int retval;
> +
> +               mutex_lock(&slot->crit_sect);

Does it make sense to introduce a helper let's say
__acpiphp_check_slot() and put there all lines inside this mutex?

> +               if (get_slot_status(slot) == ACPI_STA_ALL) {
> +                       /* remove stale devices if any */
> +                       list_for_each_entry_safe(dev, tmp,
> +                                       &bus->devices, bus_list) {
> +                               if (PCI_SLOT(dev->devfn) != slot->device)
> +                                       continue;
> +                               pci_trim_stale_devices(dev);

Perhaps

 list_for_each_entry_safe(dev, tmp, &bus->devices, bus_list) {
      if (PCI_SLOT(dev->devfn) == slot->device)
                pci_trim_stale_devices(dev);
 }

--
With Best Regards,
Andy Shevchenko
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