[PATCH v16 16/18] PCI/CXL: Expose CXL Reset as a PCI reset method

[Srirangan Madhavan <smadhavan@nvidia.com>]

Register cxl_reset with the PCI reset-method interface and place it before
FLR, which does not reset CXL.cache or CXL.mem protocol state.

Return -ENOTTY when device capabilities, function scope, cached HDM state,
or required cache synchronization do not permit a safe reset.

Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
---
 drivers/pci/cxl.c   | 12 +++++++++---
 drivers/pci/pci.c   |  1 +
 include/linux/pci.h |  2 +-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/cxl.c b/drivers/pci/cxl.c
index 58bbd5b47539..0c4ac0832b34 100644
--- a/drivers/pci/cxl.c
+++ b/drivers/pci/cxl.c
@@ -672,7 +672,7 @@ int cxl_reset_function(struct pci_dev *pdev, bool probe)
 
 	rc = cxl_pci_device_dvsec(pdev, &dvsec, &cap);
 	if (rc)
-		return rc;
+		return probe ? -ENOTTY : rc;
 	if (!(cap & PCI_DVSEC_CXL_CACHE_CAPABLE) ||
 	    !(cap & PCI_DVSEC_CXL_MEM_CAPABLE) ||
 	    !(cap & PCI_DVSEC_CXL_RST_CAPABLE) ||
@@ -681,9 +681,9 @@ int cxl_reset_function(struct pci_dev *pdev, bool probe)
 
 	rc = pci_read_config_word(pdev, dvsec + PCI_DVSEC_CXL_CTRL, &ctrl);
 	if (rc)
-		return pcibios_err_to_errno(rc);
+		return probe ? -ENOTTY : pcibios_err_to_errno(rc);
 	if (PCI_POSSIBLE_ERROR(ctrl))
-		return -ENODEV;
+		return probe ? -ENOTTY : -ENODEV;
 	if (!(ctrl & PCI_DVSEC_CXL_CACHE_ENABLE) ||
 	    !(ctrl & PCI_DVSEC_CXL_MEM_ENABLE))
 		return -ENOTTY;
@@ -706,5 +706,11 @@ int cxl_reset_function(struct pci_dev *pdev, bool probe)
 	    !IS_ENABLED(CONFIG_CXL_REGION_INVALIDATION_TEST))
 		return -ENOTTY;
 
+	/* Raw reset callers may not have saved the PCI state needed for restore. */
+	if (!pdev->state_saved) {
+		pci_err(pdev, "CXL reset requires saved PCI state\n");
+		return -EINVAL;
+	}
+
 	return cxl_reset_execute(pdev, dvsec, cap);
 }
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 9031060423cc..f5990d6cc51b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5148,6 +5148,7 @@ const struct pci_reset_fn_method pci_reset_fn_methods[] = {
 	{ },
 	{ pci_dev_specific_reset, .name = "device_specific" },
 	{ pci_dev_acpi_reset, .name = "acpi" },
+	{ cxl_reset_function, .name = "cxl_reset" },
 	{ pcie_reset_flr, .name = "flr" },
 	{ pci_af_flr, .name = "af_flr" },
 	{ pci_pm_reset, .name = "pm" },
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 7bb37fcb556d..743b57ff885a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -52,7 +52,7 @@
 			       PCI_STATUS_PARITY)
 
 /* Number of reset methods used in pci_reset_fn_methods array in pci.c */
-#define PCI_NUM_RESET_METHODS 8
+#define PCI_NUM_RESET_METHODS 9
 
 #define PCI_RESET_PROBE		true
 #define PCI_RESET_DO_RESET	false
-- 
2.43.0