Message-ID:
 <AS8PR04MB8676DE8224D6242FA0597F5C8C5EA@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Thu, 24 Jul 2025 09:28:36 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: "manivannan.sadhasivam@....qualcomm.com"
	<manivannan.sadhasivam@....qualcomm.com>, Bjorn Helgaas
	<bhelgaas@...gle.com>, Mahesh J Salgaonkar <mahesh@...ux.ibm.com>, Oliver
 O'Halloran <oohall@...il.com>, Will Deacon <will@...nel.org>, Lorenzo
 Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczy��ski
	<kwilczynski@...nel.org>, Manivannan Sadhasivam <mani@...nel.org>, Rob
 Herring <robh@...nel.org>, Heiko Stuebner <heiko@...ech.de>, Philipp Zabel
	<p.zabel@...gutronix.de>
CC: "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-arm-msm@...r.kernel.org"
	<linux-arm-msm@...r.kernel.org>, "linux-rockchip@...ts.infradead.org"
	<linux-rockchip@...ts.infradead.org>, Niklas Cassel <cassel@...nel.org>,
	Wilfred Mallawa <wilfred.mallawa@....com>, Krishna Chaitanya Chundru
	<krishna.chundru@....qualcomm.com>, Lukas Wunner <lukas@...ner.de>
Subject: RE: [PATCH v6 0/4] PCI: Add support for resetting the Root Ports in a
 platform specific way

> -----Original Message-----
> From: Manivannan Sadhasivam via B4 Relay
> <devnull+manivannan.sadhasivam.oss.qualcomm.com@...nel.org>
> Sent: 2025年7月15日 22:21
> To: Bjorn Helgaas <bhelgaas@...gle.com>; Mahesh J Salgaonkar
> <mahesh@...ux.ibm.com>; Oliver O'Halloran <oohall@...il.com>; Will
> Deacon <will@...nel.org>; Lorenzo Pieralisi <lpieralisi@...nel.org>; Krzysztof
> Wilczy��ski <kwilczynski@...nel.org>; Manivannan Sadhasivam
> <mani@...nel.org>; Rob Herring <robh@...nel.org>; Heiko Stuebner
> <heiko@...ech.de>; Philipp Zabel <p.zabel@...gutronix.de>
> Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org;
> linuxppc-dev@...ts.ozlabs.org; linux-arm-kernel@...ts.infradead.org;
> linux-arm-msm@...r.kernel.org; linux-rockchip@...ts.infradead.org; Niklas
> Cassel <cassel@...nel.org>; Wilfred Mallawa <wilfred.mallawa@....com>;
> Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>;
> mani@...nel.org; Lukas Wunner <lukas@...ner.de>; Manivannan Sadhasivam
> <manivannan.sadhasivam@....qualcomm.com>; Manivannan Sadhasivam
> <mani@...nel.org>
> Subject: [PATCH v6 0/4] PCI: Add support for resetting the Root Ports in a
> platform specific way
>
> [You don't often get email from
> devnull+manivannan.sadhasivam.oss.qualcomm.com@...nel.org. Learn why
> this is important at https://aka.ms/LearnAboutSenderIdentification ]
>
> Hi,
>
> Currently, in the event of AER/DPC, PCI core will try to reset the slot (Root
> Port) and its subordinate devices by invoking bridge control reset and FLR. But in
> some cases like AER Fatal error, it might be necessary to reset the Root Ports
> using the PCI host bridge drivers in a platform specific way (as indicated by the
> TODO in the pcie_do_recovery() function in drivers/pci/pcie/err.c).
> Otherwise, the PCI link won't be recovered successfully.
>
> So this series adds a new callback 'pci_host_bridge::reset_root_port' for the
> host bridge drivers to reset the Root Port when a fatal error happens.
>
> Also, this series allows the host bridge drivers to handle PCI link down event by
> resetting the Root Ports and recovering the bus. This is accomplished by the help
> of the new 'pci_host_handle_link_down()' API. Host bridge drivers are expected
> to call this API (preferrably from a threaded IRQ handler) with relevant Root
> Port 'pci_dev' when a link down event is detected for the port.
> The API will reuse the pcie_do_recovery() function to recover the link if AER
> support is enabled, otherwise it will directly call the reset_root_port() callback
> of the host bridge driver (if exists).
>
> For reference, I've modified the pcie-qcom driver to call
> pci_host_handle_link_down() API with Root Port 'pci_dev' after receiving the
> LINK_DOWN global_irq event and populated
> 'pci_host_bridge::reset_root_port()'
> callback to reset the Root Port. Since the Qcom PCIe controllers support only a
> single Root Port (slot) per controller instance, the API is going to be invoked only
> once. For multi Root Port controllers, the controller driver is expected to detect
> the Root Port that received the link down event and call the
> pci_host_handle_link_down() API with 'pci_dev' of that Root Port.
>
> Testing
> -------
>
> I've lost access to my test setup now. So Krishna (Cced) will help with testing on
> the Qcom platform and Wilfred or Niklas should be able to test it on Rockchip
> platform. For the moment, this series is compile tested only.
>
> Changes in v6:
> - Incorporated the patch:
> https://lore.kern/
> el.org%2Fall%2F20250524185304.26698-2-manivannan.sadhasivam%40linaro.o
> rg%2F&data=05%7C02%7Chongxing.zhu%40nxp.com%7C33c08e5bb14347e5c3
> cc08ddc3accaf5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6388
> 81869083440222%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydW
> UsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D
> %7C0%7C%7C%7C&sdata=BsEibf7v8wAQzwt%2BbgozxE0Se8vvF9lb1O%2F0Hw
> 1gG1M%3D&reserved=0
> - Link to v5:
> https://lore.kern/
> el.org%2Fr%2F20250715-pci-port-reset-v5-0-26a5d278db40%40oss.qualcomm.
> com&data=05%7C02%7Chongxing.zhu%40nxp.com%7C33c08e5bb14347e5c3c
> c08ddc3accaf5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63888
> 1869083460674%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUs
> IlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%
> 7C0%7C%7C%7C&sdata=JVUK2udmAC4GCN6%2Bg%2B7rMVhnQWJXBF972JB2
> GJMrfWc%3D&reserved=0
>
> Changes in v5:
> * Reworked the pci_host_handle_link_down() to accept Root Port instead of
>   resetting all Root Ports in the event of link down.
> * Renamed 'reset_slot' to 'reset_root_port' to avoid confusion as both terms
>   were used interchangibly and the series is intended to reset Root Port only.
> * Added the Rockchip driver change to this series.
> * Dropped the applied patches and review/tested tags due to rework.
> * Rebased on top of v6.16-rc1.
>
> Changes in v4:
> - Handled link down first in the irq handler
> - Updated ICC & OPP bandwidth after link up in reset_slot() callback
> - Link to v3:
> https://lore.kern/
> el.org%2Fr%2F20250417-pcie-reset-slot-v3-0-59a10811c962%40linaro.org&dat
> a=05%7C02%7Chongxing.zhu%40nxp.com%7C33c08e5bb14347e5c3cc08ddc3a
> ccaf5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6388818690834
> 74708%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLj
> AuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%
> 7C%7C&sdata=vEVqdgjtUCGLMpEiUoMk5wdRNPAISlpXngguyA04Tu0%3D&rese
> rved=0
>
> Changes in v3:
> - Made the pci-host-common driver as a common library for host controller
>   drivers
> - Moved the reset slot code to pci-host-common library
> - Link to v2:
> https://lore.kern/
> el.org%2Fr%2F20250416-pcie-reset-slot-v2-0-efe76b278c10%40linaro.org&dat
> a=05%7C02%7Chongxing.zhu%40nxp.com%7C33c08e5bb14347e5c3cc08ddc3a
> ccaf5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6388818690834
> 88340%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLj
> AuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%
> 7C%7C&sdata=8BFu0YVMES1iBm649E0Ollz2Ju2ZEwuxB6%2BC%2F2sO19Q%3D
> &reserved=0
>
> Changes in v2:
> - Moved calling reset_slot() callback from pcie_do_recovery() to
> pcibios_reset_secondary_bus()
> - Link to v1:
> https://lore.kern/
> el.org%2Fr%2F20250404-pcie-reset-slot-v1-0-98952918bf90%40linaro.org&dat
> a=05%7C02%7Chongxing.zhu%40nxp.com%7C33c08e5bb14347e5c3cc08ddc3a
> ccaf5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6388818690835
> 06149%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLj
> AuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%
> 7C%7C&sdata=mbs8czUH0TzbZXD9zeUTPr1QyuCx8b%2BcYRhxUTXEjUQ%3D&r
> eserved=0
>
> Signed-off-by: Manivannan Sadhasivam
> <manivannan.sadhasivam@....qualcomm.com>

[Richard Zhu] Tested-by: Richard Zhu <hongxing.zhu@....com>
Tested this v6-series patches on i.MX95 platform. At least, the PCIe link
 can be re-established successfully although AER has some complains.
Logs:
<snipped>
[   32.563020] imx6q-pcie 4c300000.pcie: Stop root bus and handle link down
[   32.570025] pcieport 0000:00:00.0: Recovering Root Port due to Link Down
[   32.578213] pci 0000:01:00.0: AER: can't recover (no error_detected callback)
[   32.586536] pci 0000:01:00.1: AER: can't recover (no error_detected callback)
[   32.898399] imx6q-pcie 4c300000.pcie: PCIe Gen.2 x1 link up
[   33.030438] pcieport 0000:00:00.0: Root Port has been reset
[   33.036133] pcieport 0000:00:00.0: AER: device recovery failed
[   33.041991] imx6q-pcie 4c300000.pcie: Rescan bus after link up is detected
[   33.050135] pcieport 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[   33.058620] pci_bus 0000:01: busn_res: [bus 01-ff] end is updated to 01
<snipped>

Best Regards
Richard Zhu

> ---
> Manivannan Sadhasivam (3):
>       PCI/ERR: Add support for resetting the Root Ports in a platform specific
> way
>       PCI: host-common: Add link down handling for Root Ports
>       PCI: qcom: Add support for resetting the Root Port due to link down
> event
>
> Wilfred Mallawa (1):
>       PCI: dw-rockchip: Add support to reset Root Port upon link down event
>
>  drivers/pci/controller/dwc/Kconfig            |   2 +
>  drivers/pci/controller/dwc/pcie-dw-rockchip.c |  91 ++++++++++++++++++-
>  drivers/pci/controller/dwc/pcie-qcom.c        | 120
> ++++++++++++++++++++++++--
>  drivers/pci/controller/pci-host-common.c      |  33 +++++++
>  drivers/pci/controller/pci-host-common.h      |   1 +
>  drivers/pci/pci.c                             |  21 +++++
>  drivers/pci/pcie/err.c                        |   6 +-
>  include/linux/pci.h                           |   1 +
>  8 files changed, 260 insertions(+), 15 deletions(-)
> ---
> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
> change-id: 20250715-pci-port-reset-4d9519570123
>
> Best regards,
> --
> Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
>
>

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