cxl: EEH support
authorDaniel Axtens <dja@axtens.net>
Fri, 14 Aug 2015 07:41:26 +0000 (17:41 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Fri, 14 Aug 2015 11:32:08 +0000 (21:32 +1000)
EEH (Enhanced Error Handling) allows a driver to recover from the
temporary failure of an attached PCI card. Enable basic CXL support
for EEH.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
drivers/misc/cxl/cxl.h
drivers/misc/cxl/pci.c
drivers/misc/cxl/vphb.c

index cda0241..6f53866 100644 (file)
@@ -726,6 +726,7 @@ int cxl_psl_purge(struct cxl_afu *afu);
 
 void cxl_stop_trace(struct cxl *cxl);
 int cxl_pci_vphb_add(struct cxl_afu *afu);
+void cxl_pci_vphb_reconfigure(struct cxl_afu *afu);
 void cxl_pci_vphb_remove(struct cxl_afu *afu);
 
 extern struct pci_driver cxl_pci_driver;
index bfbd647..03ddb2d 100644 (file)
@@ -24,6 +24,7 @@
 #include <asm/io.h>
 
 #include "cxl.h"
+#include <misc/cxl.h>
 
 
 #define CXL_PCI_VSEC_ID        0x1280
@@ -1252,10 +1253,262 @@ static void cxl_remove(struct pci_dev *dev)
        cxl_remove_adapter(adapter);
 }
 
+static pci_ers_result_t cxl_vphb_error_detected(struct cxl_afu *afu,
+                                               pci_channel_state_t state)
+{
+       struct pci_dev *afu_dev;
+       pci_ers_result_t result = PCI_ERS_RESULT_NEED_RESET;
+       pci_ers_result_t afu_result = PCI_ERS_RESULT_NEED_RESET;
+
+       /* There should only be one entry, but go through the list
+        * anyway
+        */
+       list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
+               if (!afu_dev->driver)
+                       continue;
+
+               afu_dev->error_state = state;
+
+               if (afu_dev->driver->err_handler)
+                       afu_result = afu_dev->driver->err_handler->error_detected(afu_dev,
+                                                                                 state);
+               /* Disconnect trumps all, NONE trumps NEED_RESET */
+               if (afu_result == PCI_ERS_RESULT_DISCONNECT)
+                       result = PCI_ERS_RESULT_DISCONNECT;
+               else if ((afu_result == PCI_ERS_RESULT_NONE) &&
+                        (result == PCI_ERS_RESULT_NEED_RESET))
+                       result = PCI_ERS_RESULT_NONE;
+       }
+       return result;
+}
+
+static pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
+                                              pci_channel_state_t state)
+{
+       struct cxl *adapter = pci_get_drvdata(pdev);
+       struct cxl_afu *afu;
+       pci_ers_result_t result = PCI_ERS_RESULT_NEED_RESET;
+       int i;
+
+       /* At this point, we could still have an interrupt pending.
+        * Let's try to get them out of the way before they do
+        * anything we don't like.
+        */
+       schedule();
+
+       /* If we're permanently dead, give up. */
+       if (state == pci_channel_io_perm_failure) {
+               /* Tell the AFU drivers; but we don't care what they
+                * say, we're going away.
+                */
+               for (i = 0; i < adapter->slices; i++) {
+                       afu = adapter->afu[i];
+                       cxl_vphb_error_detected(afu, state);
+               }
+               return PCI_ERS_RESULT_DISCONNECT;
+       }
+
+       /* Are we reflashing?
+        *
+        * If we reflash, we could come back as something entirely
+        * different, including a non-CAPI card. As such, by default
+        * we don't participate in the process. We'll be unbound and
+        * the slot re-probed. (TODO: check EEH doesn't blindly rebind
+        * us!)
+        *
+        * However, this isn't the entire story: for reliablity
+        * reasons, we usually want to reflash the FPGA on PERST in
+        * order to get back to a more reliable known-good state.
+        *
+        * This causes us a bit of a problem: if we reflash we can't
+        * trust that we'll come back the same - we could have a new
+        * image and been PERSTed in order to load that
+        * image. However, most of the time we actually *will* come
+        * back the same - for example a regular EEH event.
+        *
+        * Therefore, we allow the user to assert that the image is
+        * indeed the same and that we should continue on into EEH
+        * anyway.
+        */
+       if (adapter->perst_loads_image && !adapter->perst_same_image) {
+               /* TODO take the PHB out of CXL mode */
+               dev_info(&pdev->dev, "reflashing, so opting out of EEH!\n");
+               return PCI_ERS_RESULT_NONE;
+       }
+
+       /*
+        * At this point, we want to try to recover.  We'll always
+        * need a complete slot reset: we don't trust any other reset.
+        *
+        * Now, we go through each AFU:
+        *  - We send the driver, if bound, an error_detected callback.
+        *    We expect it to clean up, but it can also tell us to give
+        *    up and permanently detach the card. To simplify things, if
+        *    any bound AFU driver doesn't support EEH, we give up on EEH.
+        *
+        *  - We detach all contexts associated with the AFU. This
+        *    does not free them, but puts them into a CLOSED state
+        *    which causes any the associated files to return useful
+        *    errors to userland. It also unmaps, but does not free,
+        *    any IRQs.
+        *
+        *  - We clean up our side: releasing and unmapping resources we hold
+        *    so we can wire them up again when the hardware comes back up.
+        *
+        * Driver authors should note:
+        *
+        *  - Any contexts you create in your kernel driver (except
+        *    those associated with anonymous file descriptors) are
+        *    your responsibility to free and recreate. Likewise with
+        *    any attached resources.
+        *
+        *  - We will take responsibility for re-initialising the
+        *    device context (the one set up for you in
+        *    cxl_pci_enable_device_hook and accessed through
+        *    cxl_get_context). If you've attached IRQs or other
+        *    resources to it, they remains yours to free.
+        *
+        * You can call the same functions to release resources as you
+        * normally would: we make sure that these functions continue
+        * to work when the hardware is down.
+        *
+        * Two examples:
+        *
+        * 1) If you normally free all your resources at the end of
+        *    each request, or if you use anonymous FDs, your
+        *    error_detected callback can simply set a flag to tell
+        *    your driver not to start any new calls. You can then
+        *    clear the flag in the resume callback.
+        *
+        * 2) If you normally allocate your resources on startup:
+        *     * Set a flag in error_detected as above.
+        *     * Let CXL detach your contexts.
+        *     * In slot_reset, free the old resources and allocate new ones.
+        *     * In resume, clear the flag to allow things to start.
+        */
+       for (i = 0; i < adapter->slices; i++) {
+               afu = adapter->afu[i];
+
+               result = cxl_vphb_error_detected(afu, state);
+
+               /* Only continue if everyone agrees on NEED_RESET */
+               if (result != PCI_ERS_RESULT_NEED_RESET)
+                       return result;
+
+               cxl_context_detach_all(afu);
+               cxl_afu_deactivate_mode(afu);
+               cxl_deconfigure_afu(afu);
+       }
+       cxl_deconfigure_adapter(adapter);
+
+       return result;
+}
+
+static pci_ers_result_t cxl_pci_slot_reset(struct pci_dev *pdev)
+{
+       struct cxl *adapter = pci_get_drvdata(pdev);
+       struct cxl_afu *afu;
+       struct cxl_context *ctx;
+       struct pci_dev *afu_dev;
+       pci_ers_result_t afu_result = PCI_ERS_RESULT_RECOVERED;
+       pci_ers_result_t result = PCI_ERS_RESULT_RECOVERED;
+       int i;
+
+       if (cxl_configure_adapter(adapter, pdev))
+               goto err;
+
+       for (i = 0; i < adapter->slices; i++) {
+               afu = adapter->afu[i];
+
+               if (cxl_configure_afu(afu, adapter, pdev))
+                       goto err;
+
+               if (cxl_afu_select_best_mode(afu))
+                       goto err;
+
+               cxl_pci_vphb_reconfigure(afu);
+
+               list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
+                       /* Reset the device context.
+                        * TODO: make this less disruptive
+                        */
+                       ctx = cxl_get_context(afu_dev);
+
+                       if (ctx && cxl_release_context(ctx))
+                               goto err;
+
+                       ctx = cxl_dev_context_init(afu_dev);
+                       if (!ctx)
+                               goto err;
+
+                       afu_dev->dev.archdata.cxl_ctx = ctx;
+
+                       if (cxl_afu_check_and_enable(afu))
+                               goto err;
+
+                       afu_dev->error_state = pci_channel_io_normal;
+
+                       /* If there's a driver attached, allow it to
+                        * chime in on recovery. Drivers should check
+                        * if everything has come back OK, but
+                        * shouldn't start new work until we call
+                        * their resume function.
+                        */
+                       if (!afu_dev->driver)
+                               continue;
+
+                       if (afu_dev->driver->err_handler &&
+                           afu_dev->driver->err_handler->slot_reset)
+                               afu_result = afu_dev->driver->err_handler->slot_reset(afu_dev);
+
+                       if (afu_result == PCI_ERS_RESULT_DISCONNECT)
+                               result = PCI_ERS_RESULT_DISCONNECT;
+               }
+       }
+       return result;
+
+err:
+       /* All the bits that happen in both error_detected and cxl_remove
+        * should be idempotent, so we don't need to worry about leaving a mix
+        * of unconfigured and reconfigured resources.
+        */
+       dev_err(&pdev->dev, "EEH recovery failed. Asking to be disconnected.\n");
+       return PCI_ERS_RESULT_DISCONNECT;
+}
+
+static void cxl_pci_resume(struct pci_dev *pdev)
+{
+       struct cxl *adapter = pci_get_drvdata(pdev);
+       struct cxl_afu *afu;
+       struct pci_dev *afu_dev;
+       int i;
+
+       /* Everything is back now. Drivers should restart work now.
+        * This is not the place to be checking if everything came back up
+        * properly, because there's no return value: do that in slot_reset.
+        */
+       for (i = 0; i < adapter->slices; i++) {
+               afu = adapter->afu[i];
+
+               list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
+                       if (afu_dev->driver && afu_dev->driver->err_handler &&
+                           afu_dev->driver->err_handler->resume)
+                               afu_dev->driver->err_handler->resume(afu_dev);
+               }
+       }
+}
+
+static const struct pci_error_handlers cxl_err_handler = {
+       .error_detected = cxl_pci_error_detected,
+       .slot_reset = cxl_pci_slot_reset,
+       .resume = cxl_pci_resume,
+};
+
 struct pci_driver cxl_pci_driver = {
        .name = "cxl-pci",
        .id_table = cxl_pci_tbl,
        .probe = cxl_probe,
        .remove = cxl_remove,
        .shutdown = cxl_remove,
+       .err_handler = &cxl_err_handler,
 };
index 2930911..6dd16a6 100644 (file)
@@ -266,6 +266,14 @@ int cxl_pci_vphb_add(struct cxl_afu *afu)
        return 0;
 }
 
+void cxl_pci_vphb_reconfigure(struct cxl_afu *afu)
+{
+       /* When we are reconfigured, the AFU's MMIO space is unmapped
+        * and remapped. We need to reflect this in the PHB's view of
+        * the world.
+        */
+       afu->phb->cfg_addr = afu->afu_desc_mmio + afu->crs_offset;
+}
 
 void cxl_pci_vphb_remove(struct cxl_afu *afu)
 {