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Message-ID: <aHlBfhYvNNOfqoq1@lizhi-Precision-Tower-5810>
Date: Thu, 17 Jul 2025 14:31:26 -0400
From: Frank Li <Frank.li@....com>
To: manivannan.sadhasivam@....qualcomm.com
Cc: 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 Wilczyński <kwilczynski@...nel.org>,
Manivannan Sadhasivam <mani@...nel.org>,
Rob Herring <robh@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
Philipp Zabel <p.zabel@...gutronix.de>, 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>,
Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v6 2/4] PCI: host-common: Add link down handling for Root
Portsy
On Tue, Jul 15, 2025 at 07:51:05PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <mani@...nel.org>
>
> The PCI link, when down, needs to be recovered to bring it back. But on
> some platforms, that cannot be done in a generic way as link recovery
> procedure is platform specific. So add a new API
> pci_host_handle_link_down() that could be called by the host bridge drivers
> for a specific Root Port when the link goes down.
>
> The API accepts the 'pci_dev' corresponding to the Root Port which observed
> the link down event. If CONFIG_PCIEAER is enabled, the API calls
> pcie_do_recovery() function with 'pci_channel_io_frozen' as the state. This
> will result in the execution of the AER Fatal error handling code. Since
> the link down recovery is pretty much the same as AER Fatal error handling,
> pcie_do_recovery() helper is reused here. First, the AER error_detected()
> callback will be triggered for the bridge and then for the downstream
> devices. Finally, pci_host_reset_root_port() will be called for the Root
> Port, which will reset the Root Port using 'reset_root_port' callback to
> recover the link. Once that's done, resume message will be broadcasted to
> the bridge and the downstream devices, indicating successful link recovery.
>
> But if CONFIG_PCIEAER is not enabled in the kernel, only
> pci_host_reset_root_port() API will be called, which will in turn call
> pci_bus_error_reset() to just reset the Root Port as there is no way we
> could inform the drivers about link recovery.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
Reviewed-by: Frank Li <Frank.Li@....com>
> ---
> drivers/pci/controller/pci-host-common.c | 33 ++++++++++++++++++++++++++++++++
> drivers/pci/controller/pci-host-common.h | 1 +
> drivers/pci/pci.c | 1 +
> drivers/pci/pcie/err.c | 1 +
> 4 files changed, 36 insertions(+)
>
> diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
> index b0992325dd65f0da8e216ec8a2153af365225d1d..51eacb6cb57443338e995f17afd3b2564bbd1f83 100644
> --- a/drivers/pci/controller/pci-host-common.c
> +++ b/drivers/pci/controller/pci-host-common.c
> @@ -12,9 +12,11 @@
> #include <linux/of.h>
> #include <linux/of_address.h>
> #include <linux/of_pci.h>
> +#include <linux/pci.h>
> #include <linux/pci-ecam.h>
> #include <linux/platform_device.h>
>
> +#include "../pci.h"
> #include "pci-host-common.h"
>
> static void gen_pci_unmap_cfg(void *ptr)
> @@ -104,5 +106,36 @@ void pci_host_common_remove(struct platform_device *pdev)
> }
> EXPORT_SYMBOL_GPL(pci_host_common_remove);
>
> +static pci_ers_result_t pci_host_reset_root_port(struct pci_dev *dev)
> +{
> + int ret;
> +
> + ret = pci_bus_error_reset(dev);
> + if (ret) {
> + pci_err(dev, "Failed to reset Root Port: %d\n", ret);
> + return PCI_ERS_RESULT_DISCONNECT;
> + }
> +
> + pci_info(dev, "Root Port has been reset\n");
> +
> + return PCI_ERS_RESULT_RECOVERED;
> +}
> +
> +static void pci_host_recover_root_port(struct pci_dev *port)
> +{
> +#if IS_ENABLED(CONFIG_PCIEAER)
> + pcie_do_recovery(port, pci_channel_io_frozen, pci_host_reset_root_port);
> +#else
> + pci_host_reset_root_port(port);
> +#endif
> +}
> +
> +void pci_host_handle_link_down(struct pci_dev *port)
> +{
> + pci_info(port, "Recovering Root Port due to Link Down\n");
> + pci_host_recover_root_port(port);
> +}
> +EXPORT_SYMBOL_GPL(pci_host_handle_link_down);
> +
> MODULE_DESCRIPTION("Common library for PCI host controller drivers");
> MODULE_LICENSE("GPL v2");
> diff --git a/drivers/pci/controller/pci-host-common.h b/drivers/pci/controller/pci-host-common.h
> index 65bd9e032353827221a6af59858c46fdbe5916bf..cb0a07c8773ec87838164e994b34a62d2c8118be 100644
> --- a/drivers/pci/controller/pci-host-common.h
> +++ b/drivers/pci/controller/pci-host-common.h
> @@ -16,5 +16,6 @@ int pci_host_common_probe(struct platform_device *pdev);
> int pci_host_common_init(struct platform_device *pdev,
> const struct pci_ecam_ops *ops);
> void pci_host_common_remove(struct platform_device *pdev);
> +void pci_host_handle_link_down(struct pci_dev *port);
>
> #endif
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b29264aa2be33b18a58b3b3db1d1fb0f6483e5e8..39310422634a9551efc8aded565b7cc30f4989d0 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5768,6 +5768,7 @@ int pci_bus_error_reset(struct pci_dev *bridge)
> mutex_unlock(&pci_slot_mutex);
> return pci_bus_reset(bridge->subordinate, PCI_RESET_DO_RESET);
> }
> +EXPORT_SYMBOL_GPL(pci_bus_error_reset);
>
> /**
> * pci_probe_reset_bus - probe whether a PCI bus can be reset
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index b834fc0d705938540d3d7d3d8739770c09fe7cf1..3e3084bb7cb7fa06b526e6fab60e77927aba0ad0 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -270,3 +270,4 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>
> return status;
> }
> +EXPORT_SYMBOL_GPL(pcie_do_recovery);
>
> --
> 2.45.2
>
>
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