ice: implement direct read for NVM and Shadow RAM regions

Implement the .read handler for the NVM and Shadow RAM regions. This
enables user space to read a small chunk of the flash without needing the
overhead of creating a full snapshot.

Update the documentation for ice to detail which regions have direct read
support.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 69 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice_devlink.c b/drivers/net/ethernet/intel/ice/ice_devlink.c
index 9d3500291d2e..946d64e577c9 100644
--- a/drivers/net/ethernet/intel/ice/ice_devlink.c
+++ b/drivers/net/ethernet/intel/ice/ice_devlink.c
@@ -1688,6 +1688,73 @@ static int ice_devlink_nvm_snapshot(struct devlink *devlink,
 }
 
 /**
+ * ice_devlink_nvm_read - Read a portion of NVM flash contents
+ * @devlink: the devlink instance
+ * @ops: the devlink region to snapshot
+ * @extack: extended ACK response structure
+ * @offset: the offset to start at
+ * @size: the amount to read
+ * @data: the data buffer to read into
+ *
+ * This function is called in response to DEVLINK_CMD_REGION_READ to directly
+ * read a section of the NVM contents.
+ *
+ * It reads from either the nvm-flash or shadow-ram region contents.
+ *
+ * @returns zero on success, and updates the data pointer. Returns a non-zero
+ * error code on failure.
+ */
+static int ice_devlink_nvm_read(struct devlink *devlink,
+				const struct devlink_region_ops *ops,
+				struct netlink_ext_ack *extack,
+				u64 offset, u32 size, u8 *data)
+{
+	struct ice_pf *pf = devlink_priv(devlink);
+	struct device *dev = ice_pf_to_dev(pf);
+	struct ice_hw *hw = &pf->hw;
+	bool read_shadow_ram;
+	u64 nvm_size;
+	int status;
+
+	if (ops == &ice_nvm_region_ops) {
+		read_shadow_ram = false;
+		nvm_size = hw->flash.flash_size;
+	} else if (ops == &ice_sram_region_ops) {
+		read_shadow_ram = true;
+		nvm_size = hw->flash.sr_words * 2u;
+	} else {
+		NL_SET_ERR_MSG_MOD(extack, "Unexpected region in snapshot function");
+		return -EOPNOTSUPP;
+	}
+
+	if (offset + size >= nvm_size) {
+		NL_SET_ERR_MSG_MOD(extack, "Cannot read beyond the region size");
+		return -ERANGE;
+	}
+
+	status = ice_acquire_nvm(hw, ICE_RES_READ);
+	if (status) {
+		dev_dbg(dev, "ice_acquire_nvm failed, err %d aq_err %d\n",
+			status, hw->adminq.sq_last_status);
+		NL_SET_ERR_MSG_MOD(extack, "Failed to acquire NVM semaphore");
+		return -EIO;
+	}
+
+	status = ice_read_flat_nvm(hw, (u32)offset, &size, data,
+				   read_shadow_ram);
+	if (status) {
+		dev_dbg(dev, "ice_read_flat_nvm failed after reading %u bytes, err %d aq_err %d\n",
+			size, status, hw->adminq.sq_last_status);
+		NL_SET_ERR_MSG_MOD(extack, "Failed to read NVM contents");
+		ice_release_nvm(hw);
+		return -EIO;
+	}
+	ice_release_nvm(hw);
+
+	return 0;
+}
+
+/**
  * ice_devlink_devcaps_snapshot - Capture snapshot of device capabilities
  * @devlink: the devlink instance
  * @ops: the devlink region being snapshotted
@@ -1735,12 +1802,14 @@ static const struct devlink_region_ops ice_nvm_region_ops = {
 	.name = "nvm-flash",
 	.destructor = vfree,
 	.snapshot = ice_devlink_nvm_snapshot,
+	.read = ice_devlink_nvm_read,
 };
 
 static const struct devlink_region_ops ice_sram_region_ops = {
 	.name = "shadow-ram",
 	.destructor = vfree,
 	.snapshot = ice_devlink_nvm_snapshot,
+	.read = ice_devlink_nvm_read,
 };
 
 static const struct devlink_region_ops ice_devcaps_region_ops = {