On 10/3/2016 1:36 AM, Sinan Kaya wrote:
> The PCIE spec allows an endpoint device to extend the initialization time
> beyond 1 second by issuing Configuration Request Retry Status (CRS) for a
> vendor ID read request.
>
> This basically means "I'm busy now, please call me back later".
>
> There are two moving parts to CRS support from the SW perspective. One part
> is to determine if CRS is supported or not. The second part is to set the
> CRS visibility register.
>
> As part of the probe, the Linux kernel sets the above two conditions in
> pci_enable_crs function. The kernel is also honoring the returned CRS in
> pci_bus_read_dev_vendor_id function if supported. The function will poll up
> to specified amount of time while endpoint is returning CRS response.
>
> The PCIe spec also allows CRS to be issued during cold, warm, hot and FLR
> resets.
>
> The hot reset is initiated by starting a secondary bus reset. A bus/device
> restore follows the reset. This patch is adding vendor ID read into dev
> restore function to validate that the device is accessible before writing
> the register contents. If the device issues CRS, the code might poll up
> to 60 seconds.
>
> Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> ---
> drivers/pci/pci.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index aab9d51..c8749b9 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4020,6 +4020,12 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
>
> static void pci_dev_restore(struct pci_dev *dev)
> {
> + u32 l;
> +
> + /* see if the device is accessible first */
> + if (!pci_bus_read_dev_vendor_id(dev->bus, dev->devfn, &l, 60 * 1000))
> + return;
> +
> pci_restore_state(dev);
> pci_reset_notify(dev, false);
> }
>
Any feedback on this direction?
--
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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