From: Yicong Yang <yangyicong@huawei.com>
To: Yicong Yang <yangyicong@hisilicon.com>, <bhelgaas@google.com>,
<rafael@kernel.org>, <linux-pci@vger.kernel.org>
Cc: <linux-kernel@vger.kernel.org>, <linuxarm@huawei.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: [PATCH v5] PCI: Make sure the bus bridge powered on when scanning bus
Date: Thu, 5 May 2022 20:41:52 +0800 [thread overview]
Message-ID: <39c4793e-836f-0d94-4a0e-b3c76b1a8ce2@huawei.com> (raw)
In-Reply-To: <20220424020710.17589-1-yangyicong@hisilicon.com>
Hi Bjorn,
Any comment? Is it ok to take this?
Thanks.
On 2022/4/24 10:07, Yicong Yang wrote:
> When the bus bridge is runtime suspended, we'll fail to rescan
> the devices through sysfs as we cannot access the configuration
> space correctly when the bridge is in D3hot.
> It can be reproduced like:
>
> $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/0000:81:00.1/remove
> $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/pci_bus/0000:81/rescan
>
> 0000:80:00.0 is a Root Port and it is runtime-suspended, so
> 0000:81:00.1 is unreachable after a rescan.
>
> Power up the bridge when scanning the child bus and allow it to
> suspend again by adding pm_runtime_get_sync()/pm_runtime_put()
> in pci_scan_child_bus_extend().
>
> Cc: Rafael J. Wysocki <rafael@kernel.org>
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> Change since v4:
> - rephrase the commit suggested by Rafael
> Link: https://lore.kernel.org/lkml/20220422080404.27724-1-yangyicong@hisilicon.com/
>
> Change since v3:
> - retain the pm_runtime_*() calls in pci_scan_bridge_extend() as Rafael points
> out that it's necessary when the brigde is in D3cold
> Link: https://lore.kernel.org/linux-pci/20220414123736.34150-1-yangyicong@hisilicon.com/
>
> Change since v2:
> - just rebase it on v5.18-rc2
> Link: https://lore.kernel.org/linux-pci/1601029386-4928-1-git-send-email-yangyicong@hisilicon.com/
>
> Change since v1:
> - use an intermediate variable *bridge as suggested
> - remove the pm_runtime_*() calls in pci_scan_bridge_extend()
> Link: https://lore.kernel.org/linux-pci/1596022223-4765-1-git-send-email-yangyicong@hisilicon.com/
>
> drivers/pci/probe.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 17a969942d37..b108e72b6586 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2859,11 +2859,20 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
> unsigned int used_buses, normal_bridges = 0, hotplug_bridges = 0;
> unsigned int start = bus->busn_res.start;
> unsigned int devfn, fn, cmax, max = start;
> + struct pci_dev *bridge = bus->self;
> struct pci_dev *dev;
> int nr_devs;
>
> dev_dbg(&bus->dev, "scanning bus\n");
>
> + /*
> + * Make sure the bus bridge is powered on, otherwise we may not be
> + * able to scan the devices as we may fail to access the configuration
> + * space of subordinates.
> + */
> + if (bridge)
> + pm_runtime_get_sync(&bridge->dev);
> +
> /* Go find them, Rover! */
> for (devfn = 0; devfn < 256; devfn += 8) {
> nr_devs = pci_scan_slot(bus, devfn);
> @@ -2976,6 +2985,9 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
> }
> }
>
> + if (bridge)
> + pm_runtime_put(&bridge->dev);
> +
> /*
> * We've scanned the bus and so we know all about what's on
> * the other side of any bridges that may be on this bus plus
>
prev parent reply other threads:[~2022-05-05 12:42 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-24 2:07 [PATCH v5] PCI: Make sure the bus bridge powered on when scanning bus Yicong Yang
2022-05-05 12:41 ` Yicong Yang [this message]
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