linux-kernel - Re: [PATCH 1/5] PCI: endpoint: Add linkdown notifier support

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Date:   Wed, 16 Jun 2021 23:52:28 +0530
From:   Om Prakash Singh <omp@...dia.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <kishon@...com>, <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <hemantk@...eaurora.org>,
        <smohanad@...eaurora.org>
Subject: Re: [PATCH 1/5] PCI: endpoint: Add linkdown notifier support



On 6/16/2021 5:29 PM, Manivannan Sadhasivam wrote:
> External email: Use caution opening links or attachments
> 
> 
> Add support to notify the EPF device about the linkdown event from the
> EPC device.
> 
> Usage:
> ======
> 
> EPC
> ---
> 
> ```
> static irqreturn_t pcie_ep_irq(int irq, void *data)
> {
> ...
>          case PCIE_EP_INT_LINK_DOWN:
>                  pci_epc_linkdown(epc);
>                  break;
Can you provide use case/scenario when epc will get LINK_DOWN interrupt?

> ...
> }
> ```
> 
> EPF
> ---
> 
> ```
> static int pci_epf_notifier(struct notifier_block *nb, unsigned long val,
>                              void *data)
> {
> ...
>          case LINK_DOWN:
>                  /* Handle link down event */
>                  break;
> ...
> }
> ```
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>   drivers/pci/endpoint/pci-epc-core.c | 17 +++++++++++++++++
>   include/linux/pci-epc.h             |  1 +
>   include/linux/pci-epf.h             |  1 +
>   3 files changed, 19 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index adec9bee72cf..f29d78c18438 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -641,6 +641,23 @@ void pci_epc_linkup(struct pci_epc *epc)
>   }
>   EXPORT_SYMBOL_GPL(pci_epc_linkup);
> 
> +/**
> + * pci_epc_linkdown() - Notify the EPF device that EPC device has dropped the
> + *                     connection with the Root Complex.
> + * @epc: the EPC device which has dropped the link with the host
> + *
> + * Invoke to Notify the EPF device that the EPC device has dropped the
> + * connection with the Root Complex.
> + */
> +void pci_epc_linkdown(struct pci_epc *epc)
> +{
> +       if (!epc || IS_ERR(epc))
> +               return;
> +
> +       atomic_notifier_call_chain(&epc->notifier, LINK_DOWN, NULL);
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_linkdown);
> +
>   /**
>    * pci_epc_init_notify() - Notify the EPF device that EPC device's core
>    *                        initialization is completed.
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index b82c9b100e97..23590efc13e7 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -202,6 +202,7 @@ void pci_epc_destroy(struct pci_epc *epc);
>   int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf,
>                      enum pci_epc_interface_type type);
>   void pci_epc_linkup(struct pci_epc *epc);
> +void pci_epc_linkdown(struct pci_epc *epc);
>   void pci_epc_init_notify(struct pci_epc *epc);
>   void pci_epc_remove_epf(struct pci_epc *epc, struct pci_epf *epf,
>                          enum pci_epc_interface_type type);
> diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> index 6833e2160ef1..e9ad634b1575 100644
> --- a/include/linux/pci-epf.h
> +++ b/include/linux/pci-epf.h
> @@ -20,6 +20,7 @@ enum pci_epc_interface_type;
>   enum pci_notify_event {
>          CORE_INIT,
>          LINK_UP,
> +       LINK_DOWN,
>   };
> 
>   enum pci_barno {
> --
> 2.25.1
>