[PATCH v6 1/4] PCI/ERR: Add support for resetting the Root Ports in a platform specific way

[Manivannan Sadhasivam via B4 Relay]

From: Manivannan Sadhasivam <m...@kernel.org>

Some host bridge devices require resetting the Root Ports in a platform
specific way to recover them from error conditions such as Fatal AER
errors, Link Down etc... So introduce pci_host_bridge::reset_root_port()
callback and call it from pcibios_reset_secondary_bus() if available. Also,
save the Root Port config space before reset and restore it afterwards.

The 'reset_root_port' callback is responsible for resetting the given Root
Port referenced by the 'pci_dev' pointer in a platform specific way and
bring it back to the working state if possible. If any error occurs during
the reset operation, relevant errno should be returned.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasi...@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasi...@oss.qualcomm.com>
---
 drivers/pci/pci.c      | 20 ++++++++++++++++++++
 drivers/pci/pcie/err.c |  5 -----
 include/linux/pci.h    |  1 +
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 
e9448d55113bdfd2263d8e2f6b3ec802f56b712e..b29264aa2be33b18a58b3b3db1d1fb0f6483e5e8
 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4964,6 +4964,26 @@ void pci_reset_secondary_bus(struct pci_dev *dev)
 
 void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
 {
+       struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
+       int ret;
+
+       if (pci_is_root_bus(dev->bus) && host->reset_root_port) {
+               /*
+                * Save the config space of the Root Port before doing the
+                * reset, since the state could be lost. The Endpoint state
+                * should've been saved by the caller.
+                */
+               pci_save_state(dev);
+               ret = host->reset_root_port(host, dev);
+               if (ret)
+                       pci_err(dev, "Failed to reset Root Port: %d\n", ret);
+               else
+                       /* Now restore it on success */
+                       pci_restore_state(dev);
+
+               return;
+       }
+
        pci_reset_secondary_bus(dev);
 }
 
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index 
de6381c690f5c21f00021cdc7bde8d93a5c7db52..b834fc0d705938540d3d7d3d8739770c09fe7cf1
 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -234,11 +234,6 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
        }
 
        if (status == PCI_ERS_RESULT_NEED_RESET) {
-               /*
-                * TODO: Should call platform-specific
-                * functions to reset slot before calling
-                * drivers' slot_reset callbacks?
-                */
                status = PCI_ERS_RESULT_RECOVERED;
                pci_dbg(bridge, "broadcast slot_reset message\n");
                pci_walk_bridge(bridge, report_slot_reset, &status);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 
05e68f35f39238f8b9ce08df97b384d1c1e89bbe..e7c118a961910a307ec365f17b8fe4f2585267e8
 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -599,6 +599,7 @@ struct pci_host_bridge {
        void (*release_fn)(struct pci_host_bridge *);
        int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev 
*dev);
        void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev 
*dev);
+       int (*reset_root_port)(struct pci_host_bridge *bridge, struct pci_dev 
*dev);
        void            *release_data;
        unsigned int    ignore_reset_delay:1;   /* For entire hierarchy */
        unsigned int    no_ext_tags:1;          /* No Extended Tags */

-- 
2.45.2