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    SubjectRe: [PATCH v15 8/9] PCI/DPC: Unify and plumb error handling into DPC
    On Thu, May 03, 2018 at 01:03:57AM -0400, Oza Pawandeep wrote:
    > Current DPC driver does not do recovery, e.g. calling end-point's driver's
    > callbacks, which sanitize the sw.
    >
    > DPC driver implements link_reset callback, and calls pci_do_recovery().
    >
    > Signed-off-by: Oza Pawandeep <poza@codeaurora.org>
    >
    > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
    > index 80ec384..aed7c9f 100644
    > --- a/drivers/pci/pcie/dpc.c
    > +++ b/drivers/pci/pcie/dpc.c
    > @@ -73,29 +73,21 @@ static void dpc_wait_link_inactive(struct dpc_dev *dpc)
    > pcie_wait_for_link(pdev, false);
    > }
    >
    > -static void dpc_work(struct work_struct *work)
    > +static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
    > {
    > - struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
    > - struct pci_dev *dev, *temp, *pdev = dpc->dev->port;
    > - struct pci_bus *parent = pdev->subordinate;
    > - u16 cap = dpc->cap_pos, ctl;
    > -
    > - pci_lock_rescan_remove();
    > - list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
    > - bus_list) {
    > - pci_dev_get(dev);
    > - pci_dev_set_disconnected(dev, NULL);
    > - if (pci_has_subordinate(dev))
    > - pci_walk_bus(dev->subordinate,
    > - pci_dev_set_disconnected, NULL);
    > - pci_stop_and_remove_bus_device(dev);
    > - pci_dev_put(dev);
    > - }
    > - pci_unlock_rescan_remove();

    I think it would be good to have a comment here about why this "reset_link"
    function doesn't actually reset the link, e.g.,

    /*
    * DPC disables the Link automatically in hardware, so it has
    * already been reset by the time we get here.
    */

    > + struct dpc_dev *dpc;
    > + struct pcie_device *pciedev;
    > + struct device *devdpc;
    > + u16 cap, ctl;
    > +
    > + devdpc = pcie_port_find_device(pdev, PCIE_PORT_SERVICE_DPC);
    > + pciedev = to_pcie_device(devdpc);
    > + dpc = get_service_data(pciedev);
    > + cap = dpc->cap_pos;

    And maybe one about waiting until the link is inactive, then clearing DPC
    Trigger Status to allow the port to leave DPC.

    > dpc_wait_link_inactive(dpc);
    > if (dpc->rp_extensions && dpc_wait_rp_inactive(dpc))
    > - return;
    > + return PCI_ERS_RESULT_DISCONNECT;
    > if (dpc->rp_extensions && dpc->rp_pio_status) {
    > pci_write_config_dword(pdev, cap + PCI_EXP_DPC_RP_PIO_STATUS,
    > dpc->rp_pio_status);
    > @@ -108,6 +100,17 @@ static void dpc_work(struct work_struct *work)
    > pci_read_config_word(pdev, cap + PCI_EXP_DPC_CTL, &ctl);
    > pci_write_config_word(pdev, cap + PCI_EXP_DPC_CTL,
    > ctl | PCI_EXP_DPC_CTL_INT_EN);
    > +
    > + return PCI_ERS_RESULT_RECOVERED;
    > +}
    > +
    > +static void dpc_work(struct work_struct *work)
    > +{
    > + struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
    > + struct pci_dev *pdev = dpc->dev->port;
    > +
    > + /* From DPC point of view error is always FATAL. */
    > + pcie_do_recovery(pdev, DPC_FATAL);
    > }
    >
    > static void dpc_process_rp_pio_error(struct dpc_dev *dpc)
    > @@ -288,6 +291,7 @@ static struct pcie_port_service_driver dpcdriver = {
    > .service = PCIE_PORT_SERVICE_DPC,
    > .probe = dpc_probe,
    > .remove = dpc_remove,
    > + .reset_link = dpc_reset_link,
    > };
    >
    > static int __init dpc_service_init(void)
    > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
    > index 877785d..526aba8 100644
    > --- a/drivers/pci/pcie/err.c
    > +++ b/drivers/pci/pcie/err.c
    > @@ -181,11 +181,12 @@ static pci_ers_result_t default_reset_link(struct pci_dev *dev)
    > return PCI_ERS_RESULT_RECOVERED;
    > }
    >
    > -static pci_ers_result_t reset_link(struct pci_dev *dev)
    > +static pci_ers_result_t reset_link(struct pci_dev *dev, int severity)
    > {
    > struct pci_dev *udev;
    > pci_ers_result_t status;
    > struct pcie_port_service_driver *driver;
    > + u32 service;
    >
    > if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
    > /* Reset this port for all subordinates */
    > @@ -196,7 +197,12 @@ static pci_ers_result_t reset_link(struct pci_dev *dev)
    > }
    >
    > /* Use the aer driver of the component firstly */
    > - driver = pcie_port_find_service(udev, PCIE_PORT_SERVICE_AER);
    > + if (severity == DPC_FATAL)
    > + service = PCIE_PORT_SERVICE_DPC;
    > + else
    > + service = PCIE_PORT_SERVICE_AER;
    > +
    > + driver = pcie_port_find_service(udev, service);

    This is where I was wondering about passing in "service" directly instead
    of "severity".

    > if (driver && driver->reset_link) {
    > status = driver->reset_link(udev);
    > @@ -302,7 +308,7 @@ static pci_ers_result_t do_fatal_recovery(struct pci_dev *dev, int severity)
    > pci_dev_put(pdev);
    > }
    >
    > - result = reset_link(udev);
    > + result = reset_link(udev, severity);
    > if (result == PCI_ERS_RESULT_RECOVERED)
    > if (pcie_wait_for_link(udev, true))
    > pci_rescan_bus(udev->bus);
    > @@ -326,7 +332,8 @@ void pcie_do_recovery(struct pci_dev *dev, int severity)
    > pci_ers_result_t status;
    > enum pci_channel_state state;
    >
    > - if (severity == AER_FATAL) {
    > + if ((severity == AER_FATAL) ||
    > + (severity == DPC_FATAL)) {
    > status = do_fatal_recovery(dev, severity);
    > if (status != PCI_ERS_RESULT_RECOVERED)
    > goto failed;
    > diff --git a/include/linux/aer.h b/include/linux/aer.h
    > index 8f87bbe..0c506fe 100644
    > --- a/include/linux/aer.h
    > +++ b/include/linux/aer.h
    > @@ -14,6 +14,7 @@
    > #define AER_NONFATAL 0
    > #define AER_FATAL 1
    > #define AER_CORRECTABLE 2
    > +#define DPC_FATAL 4
    >
    > struct pci_dev;
    >
    > --
    > 2.7.4
    >

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