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

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Date:	Wed, 26 Jun 2013 12:39:30 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	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

Andy Shevchenko wrote:
> 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?

No. Why?

> > +               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);
>  }

Makes sense, thanks.

-- 
 Kirill A. Shutemov
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