[PATCH v4 08/10] cxl: add DVSEC config save/restore

[<smadhavan@nvidia.com>]

From: Srirangan Madhavan <smadhavan@nvidia.com>

Save and restore CXL DVSEC control registers across reset with
CONFIG_LOCK handling so RWL fields are preserved when locked. This
maintains device policy and capability state across cxl_reset while
avoiding writes to locked fields.

Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
---
 drivers/cxl/pci.c | 107 ++++++++++++++++++++++++++++++++++++++++++++++
 include/cxl/pci.h |  15 +++++++
 2 files changed, 122 insertions(+)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index f9cc452ccb8a..7d6a0ef70b2d 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -1154,6 +1154,113 @@ static int cxl_region_flush_host_cpu_caches(struct device *dev, void *data)
 	return 0;
 }

+/*
+ * CXL DVSEC register save/restore
+ */
+static int cxl_save_dvsec_state(struct pci_dev *pdev,
+				struct cxl_type2_saved_state *state, int dvsec)
+{
+	int rc;
+
+	rc = pci_read_config_word(pdev, dvsec + CXL_DVSEC_CTRL_OFFSET,
+				  &state->dvsec_ctrl);
+	if (rc)
+		return rc;
+
+	rc = pci_read_config_word(pdev, dvsec + CXL_DVSEC_CTRL2_OFFSET,
+				  &state->dvsec_ctrl2);
+	return rc;
+}
+
+static int cxl_restore_dvsec_state(struct pci_dev *pdev,
+				   const struct cxl_type2_saved_state *state,
+				   int dvsec, bool config_locked)
+{
+	int rc;
+	u16 val_to_restore;
+
+	if (config_locked) {
+		u16 current_val;
+
+		rc = pci_read_config_word(pdev, dvsec + CXL_DVSEC_CTRL_OFFSET,
+					  &current_val);
+		if (rc)
+			return rc;
+
+		val_to_restore = (current_val & CXL_DVSEC_CTRL_RWL_MASK) |
+				 (state->dvsec_ctrl & ~CXL_DVSEC_CTRL_RWL_MASK);
+	} else {
+		val_to_restore = state->dvsec_ctrl;
+	}
+
+	rc = pci_write_config_word(pdev, dvsec + CXL_DVSEC_CTRL_OFFSET,
+				   val_to_restore);
+	if (rc)
+		return rc;
+
+	rc = pci_write_config_word(pdev, dvsec + CXL_DVSEC_CTRL2_OFFSET,
+				   state->dvsec_ctrl2);
+	return rc;
+}
+
+/**
+ * cxl_config_save_state - Save CXL configuration state
+ * @pdev: PCI device
+ * @state: Structure to store saved state
+ *
+ * Saves CXL DVSEC state before reset.
+ */
+int cxl_config_save_state(struct pci_dev *pdev,
+			  struct cxl_type2_saved_state *state)
+{
+	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
+	int dvsec;
+
+	if (!cxlds || !state)
+		return -EINVAL;
+
+	memset(state, 0, sizeof(*state));
+
+	dvsec = cxlds->cxl_dvsec;
+	if (!dvsec)
+		return -ENODEV;
+
+	return cxl_save_dvsec_state(pdev, state, dvsec);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_config_save_state, "CXL");
+
+/**
+ * cxl_config_restore_state - Restore CXL configuration state
+ * @pdev: PCI device
+ * @state: Previously saved state
+ *
+ * Restores CXL DVSEC state after reset.
+ */
+int cxl_config_restore_state(struct pci_dev *pdev,
+			     const struct cxl_type2_saved_state *state)
+{
+	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
+	bool config_locked;
+	int rc, dvsec;
+	u16 lock_reg;
+
+	if (!cxlds || !state)
+		return -EINVAL;
+
+	dvsec = cxlds->cxl_dvsec;
+	if (!dvsec)
+		return -ENODEV;
+
+	rc = pci_read_config_word(pdev, dvsec + CXL_DVSEC_LOCK_OFFSET, &lock_reg);
+	if (rc)
+		return rc;
+
+	config_locked = !!(lock_reg & CXL_DVSEC_LOCK_CONFIG_LOCK);
+
+	return cxl_restore_dvsec_state(pdev, state, dvsec, config_locked);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_config_restore_state, "CXL");
+
 static int cxl_check_region_driver_bound(struct device *dev, void *data)
 {
 	struct cxl_decoder *cxld = to_cxl_decoder(dev);
diff --git a/include/cxl/pci.h b/include/cxl/pci.h
index 71d8de5de948..2c629ded73cc 100644
--- a/include/cxl/pci.h
+++ b/include/cxl/pci.h
@@ -4,6 +4,18 @@
 #ifndef __CXL_ACCEL_PCI_H
 #define __CXL_ACCEL_PCI_H

+/* CXL Type 2 device state for save/restore across reset */
+struct cxl_type2_saved_state {
+	/* DVSEC registers */
+	u16 dvsec_ctrl;
+	u16 dvsec_ctrl2;
+};
+
+int cxl_config_save_state(struct pci_dev *pdev,
+			  struct cxl_type2_saved_state *state);
+int cxl_config_restore_state(struct pci_dev *pdev,
+			     const struct cxl_type2_saved_state *state);
+
 /*
  * See section 8.1 Configuration Space Registers in the CXL 2.0
  * Specification. Names are taken straight from the specification with "CXL" and
@@ -23,6 +35,7 @@
 #define     CXL_DVSEC_CXL_RST_MEM_CLR_CAPABLE	BIT(11)
 #define   CXL_DVSEC_CTRL_OFFSET		0xC
 #define     CXL_DVSEC_MEM_ENABLE	BIT(2)
+#define     CXL_DVSEC_CTRL_RWL_MASK	0x5FED
 #define   CXL_DVSEC_CTRL2_OFFSET	0x10
 #define     CXL_DVSEC_DISABLE_CACHING	BIT(0)
 #define     CXL_DVSEC_INIT_CACHE_WBI	BIT(1)
@@ -32,6 +45,8 @@
 #define     CXL_DVSEC_CACHE_INVALID	BIT(0)
 #define     CXL_DVSEC_CXL_RST_COMPLETE	BIT(1)
 #define     CXL_DVSEC_CXL_RESET_ERR	BIT(2)
+#define   CXL_DVSEC_LOCK_OFFSET		0x14
+#define     CXL_DVSEC_LOCK_CONFIG_LOCK	BIT(0)
 #define   CXL_DVSEC_RANGE_SIZE_HIGH(i)	(0x18 + ((i) * 0x10))
 #define   CXL_DVSEC_RANGE_SIZE_LOW(i)	(0x1C + ((i) * 0x10))
 #define     CXL_DVSEC_MEM_INFO_VALID	BIT(0)
--
2.34.1