linux-kernel - Re: [PATCH v3 0/2] PCI: Reduce FLR delay to 10ms for MSFT devices

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Message-ID: <ccclacbxzdarqy27wlwqqcsogbrodwwslt7t5sp64xvqpa3wsl@xs5cllh7a6ft>
Date: Fri, 13 Jun 2025 17:12:48 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: grwhyte@...ux.microsoft.com
Cc: linux-pci@...r.kernel.org, shyamsaini@...ux.microsoft.com, 
	code@...icks.com, Okaya@...nel.org, bhelgaas@...gle.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] PCI: Reduce FLR delay to 10ms for MSFT devices

On Wed, Jun 11, 2025 at 12:05:50AM +0000, grwhyte@...ux.microsoft.com wrote:
> From: Graham Whyte <grwhyte@...ux.microsoft.com>
> 
> Add a new flr_delay member of the pci_dev struct to allow customization of
> the delay after FLR for devices that do not support immediate readiness
> or readiness time reporting. The main scenario this addresses is VF
> removal and rescan during runtime repairs and driver updates, which,
> if fixed to 100ms, introduces significant delays across multiple VFs.
> These delays are unnecessary for devices that complete the FLR well
> within this timeframe.
> 

I don't think it is acceptable to *reduce* the standard delay just because your
device completes it more quickly. Proper way to reduce the timing would be to
support FRS as you said, but we cannot have arbitrary delays for random devices.

- Mani

> Patch 1 adds the flr_delay member to the pci_dev struct
> Patch 2 adds the msft device specific quirk to utilize the flr_delay
> 
> ---
> v2->v3:
> - Removed Microsoft specific pcie reset reset, replaced with customizable flr_delay parameter
> - Changed msleep in pcie_flr to usleep_range to support flr delays of under 20ms 
> v1->v2:
> - Removed unnecessary EXPORT_SYMBOL_GPL for function pci_dev_wait
> - Link to thread:https://lore.kernel.org/linux-pci/?q=f%3Agrwhyte&x=t#m7453647902a1b22840f5e39434a631fd7b2515ce'
> 
> Link to V1: https://lore.kernel.org/linux-pci/20250522085253.GN7435@unreal/T/#m7453647902a1b22840f5e39434a631fd7b2515ce  
> 
> Graham Whyte (2):
>   PCI: Add flr_delay parameter to pci_dev struct
>   PCI: Reduce FLR delay to 10ms for MSFT devices
> 
>  drivers/pci/pci.c    |  8 ++++++--
>  drivers/pci/pci.h    |  2 ++
>  drivers/pci/quirks.c | 20 ++++++++++++++++++++
>  include/linux/pci.h  |  1 +
>  4 files changed, 29 insertions(+), 2 deletions(-)
> 
> -- 
> 2.25.1
> 
> 

-- 
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