From: Thierry Reding <treding@nvidia.com>
To: Vidya Sagar <vidyas@nvidia.com>
Cc: <bhelgaas@google.com>, <lorenzo.pieralisi@arm.com>,
<jonathanh@nvidia.com>, <linux-tegra@vger.kernel.org>,
<linux-pci@vger.kernel.org>, <kthota@nvidia.com>,
<mmaddireddy@nvidia.com>, <sagar.tv@gmail.com>,
Sinan Kaya <okaya@kernel.org>
Subject: Re: [PATCH] PCI: Add CRS timeout for pci_device_is_present()
Date: Mon, 14 Oct 2019 10:20:23 +0200 [thread overview]
Message-ID: <20191014082023.GA232162@ulmo> (raw)
In-Reply-To: <20191005182129.32538-1-vidyas@nvidia.com>
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On Sat, Oct 05, 2019 at 11:51:29PM +0530, Vidya Sagar wrote:
> Adds a 60 seconds timeout to consider CRS (Configuration request Retry
> Status) from a downstream device when Vendor ID read is attempted by
> an upstream device. This helps to work with devices that return CRS
> during system resume. This also makes pci_device_is_present() consistent
> with the probe path where 60 seconds timeout is already being used.
>
> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
> ---
> drivers/pci/pci.c | 3 ++-
> drivers/pci/pci.h | 2 ++
> drivers/pci/probe.c | 2 +-
> 3 files changed, 5 insertions(+), 2 deletions(-)
I think this makes sense, so:
Reviewed-by: Thierry Reding <treding@nvidia.com>
However, it looks like Sinan has researched this extensively in the past
and gave a presentation on this at Plumbers in 2017:
https://blog.linuxplumbersconf.org/2017/ocw/system/presentations/4732/original/crs.pdf
Adding Sinan to see if he has any concerns about this, since resume time
is explicitly mentioned in the above slides.
Thierry
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 95dc78ebdded..3ab9f6d3c8a6 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5905,7 +5905,8 @@ bool pci_device_is_present(struct pci_dev *pdev)
>
> if (pci_dev_is_disconnected(pdev))
> return false;
> - return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0);
> + return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v,
> + PCI_CRS_TIMEOUT);
> }
> EXPORT_SYMBOL_GPL(pci_device_is_present);
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 3f6947ee3324..aa25c5fdc6a5 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -4,6 +4,8 @@
>
> #include <linux/pci.h>
>
> +#define PCI_CRS_TIMEOUT (60 * 1000) /* 60 sec*/
> +
> #define PCI_FIND_CAP_TTL 48
>
> #define PCI_VSEC_ID_INTEL_TBT 0x1234 /* Thunderbolt */
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 7c5d68b807ef..6e44a03283c8 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2258,7 +2258,7 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
> struct pci_dev *dev;
> u32 l;
>
> - if (!pci_bus_read_dev_vendor_id(bus, devfn, &l, 60*1000))
> + if (!pci_bus_read_dev_vendor_id(bus, devfn, &l, PCI_CRS_TIMEOUT))
> return NULL;
>
> dev = pci_alloc_dev(bus);
> --
> 2.17.1
>
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next prev parent reply other threads:[~2019-10-14 8:20 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-05 18:21 [PATCH] PCI: Add CRS timeout for pci_device_is_present() Vidya Sagar
2019-10-14 8:20 ` Thierry Reding [this message]
2019-10-14 20:21 ` Sinan Kaya
2019-10-15 9:30 ` Thierry Reding
2019-10-15 11:10 ` Sinan Kaya
2019-10-15 12:14 ` Vidya Sagar
[not found] ` <afa16546-e63d-6eba-8be0-8e52339cd100@nvidia.com>
2019-10-25 11:58 ` Vidya Sagar
2019-10-26 13:59 ` Sinan Kaya
2019-11-04 11:43 ` Vidya Sagar
2019-11-04 16:52 ` Lorenzo Pieralisi
2019-11-04 17:39 ` Bjorn Helgaas
2019-11-05 10:55 ` Rafael J. Wysocki
2019-11-06 16:41 ` Bjorn Helgaas
2019-11-11 6:01 ` Vidya Sagar
2019-11-11 22:32 ` Bjorn Helgaas
2019-11-12 12:59 ` Thierry Reding
2019-11-12 14:21 ` Bjorn Helgaas
2019-11-12 17:59 ` Vidya Sagar
2019-11-12 18:58 ` Bjorn Helgaas
2019-11-13 5:39 ` Vidya Sagar
2019-11-13 11:20 ` Thierry Reding
2019-11-14 18:36 ` Bjorn Helgaas
2019-11-15 10:04 ` Vidya Sagar
2019-11-15 22:36 ` Bjorn Helgaas
2019-11-18 15:18 ` Vidya Sagar
2019-11-12 17:59 ` Vidya Sagar
2019-10-15 12:03 ` Vidya Sagar
2019-10-15 11:34 ` Vidya Sagar
2019-10-14 10:45 ` Andrew Murray
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