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

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Date:   Thu, 17 Jun 2021 00:00:17 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Om Prakash Singh <omp@...dia.com>
Cc:     kishon@...com, lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        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 Wed, Jun 16, 2021 at 11:52:28PM +0530, Om Prakash Singh wrote:
> 
> 
> 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?
> 

During host shutdown/reboot epc will get LINK_DOWN interrupt. And in our MHI
function we need to catch that for handling the SYSERR state as per the spec.

Thanks,
Mani

> > ...
> > }
> > ```
> > 
> > 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
> >