[PATCH 6/7] tg3: normalize inherited M3000 register byte order

[Magnus Lindholm <linmag7@gmail.com>]

M3000 firmware can leave BCM5718 vendor registers byte-swapped while
standard PCI fields retain normal byte order. Match the Fujitsu 10cf:165a
subsystem, IKKAKU model and swapped revision/product signature before
restoring host control; reject failed PCI accesses or register readbacks.

Keep this in probe so failures can abort initialization; SPARC firmware
enumeration skips PCI_FIXUP_EARLY. Normal rebinds and other platforms
retain their existing path.

Use tg3.h's MISC_HOST_CTRL_BYTE_SWAP and TG3PCI_GEN2_PRODID_ASICREV;
the inherited state was observed on M3000 hardware.

Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
---
 drivers/net/ethernet/broadcom/tg3.c | 91 ++++++++++++++++++++++++++++-
 1 file changed, 89 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index 73a4b569b03e..9335bcc0d8d3 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -56,6 +56,7 @@
 #include <linux/hwmon-sysfs.h>
 #include <linux/crc32.h>
 #include <linux/dmi.h>
+#include <linux/of.h>
 
 #include <net/checksum.h>
 #include <net/gso.h>
@@ -16248,6 +16249,83 @@ static bool tg3_10_100_only_device(struct tg3 *tp,
 	return false;
 }
 
+/* M3000 firmware can leave the on-board BCM5718 registers byte-swapped. */
+static bool tg3_is_m3000(struct pci_dev *pdev)
+{
+	struct device_node *root;
+	const char *model;
+	bool match;
+
+	if (pdev->vendor != PCI_VENDOR_ID_BROADCOM ||
+	    pdev->device != TG3PCI_DEVICE_TIGON3_5718 ||
+	    pdev->subsystem_vendor != 0x10cf ||
+	    pdev->subsystem_device != 0x165a)
+		return false;
+
+	root = of_find_node_by_path("/");
+	match = !of_property_read_string(root, "model", &model) &&
+		!strcmp(model, "IKKAKU");
+	of_node_put(root);
+	return match;
+}
+
+static int tg3_m3000_fw_byteorder(struct tg3 *tp, u32 *misc_ctrl_reg)
+{
+	struct pci_dev *pdev = tp->pdev;
+	u32 prodid, expected_prodid, normalized, readback;
+	int reg, err;
+
+	if (!tg3_is_m3000(pdev) ||
+	    (swab32(*misc_ctrl_reg) >> 28) != ASIC_REV_USE_PROD_ID_REG ||
+	    !(swab32(*misc_ctrl_reg) & MISC_HOST_CTRL_BYTE_SWAP))
+		return 0;
+
+	/* Standard PCI fields are normal; verify the swapped vendor registers. */
+	reg = TG3PCI_GEN2_PRODID_ASICREV;
+	err = pci_read_config_dword(pdev, reg, &prodid);
+	if (err)
+		goto config_error;
+	expected_prodid = swab32(prodid);
+	if ((expected_prodid >> 12) != ASIC_REV_5717) {
+		dev_err(&pdev->dev, "M3000: unexpected swapped product ID %08x\n",
+			prodid);
+		return -ENODEV;
+	}
+
+	normalized = (swab32(*misc_ctrl_reg) & MISC_HOST_CTRL_CHIPREV) |
+		     tp->misc_host_ctrl;
+	reg = TG3PCI_MISC_HOST_CTRL;
+	err = pci_write_config_dword(pdev, reg, swab32(normalized));
+	if (err)
+		goto config_error;
+	err = pci_read_config_dword(pdev, reg, &readback);
+	if (err)
+		goto config_error;
+	if (readback != normalized) {
+		dev_err(&pdev->dev, "M3000: host-control readback mismatch %08x\n",
+			readback);
+		return -EIO;
+	}
+
+	reg = TG3PCI_GEN2_PRODID_ASICREV;
+	err = pci_read_config_dword(pdev, reg, &prodid);
+	if (err)
+		goto config_error;
+	if (prodid != expected_prodid) {
+		dev_err(&pdev->dev, "M3000: product-ID readback mismatch %08x\n",
+			prodid);
+		return -EIO;
+	}
+	*misc_ctrl_reg = readback;
+	dev_info(&pdev->dev, "M3000: normalized firmware register byte order\n");
+	return 0;
+
+config_error:
+	dev_err(&pdev->dev, "M3000: PCI config access at %#x failed (%d)\n",
+		reg, err);
+	return pcibios_err_to_errno(err);
+}
+
 static int tg3_get_invariants(struct tg3 *tp, const struct pci_device_id *ent)
 {
 	u32 misc_ctrl_reg;
@@ -16272,8 +16350,17 @@ static int tg3_get_invariants(struct tg3 *tp, const struct pci_device_id *ent)
 	 * sure that indirect register accesses are enabled before
 	 * the first operation.
 	 */
-	pci_read_config_dword(tp->pdev, TG3PCI_MISC_HOST_CTRL,
-			      &misc_ctrl_reg);
+	err = pci_read_config_dword(tp->pdev, TG3PCI_MISC_HOST_CTRL,
+				    &misc_ctrl_reg);
+	if (err && tg3_is_m3000(tp->pdev)) {
+		dev_err(&tp->pdev->dev, "PCI host-control read failed (%d)\n",
+			err);
+		return pcibios_err_to_errno(err);
+	}
+	err = tg3_m3000_fw_byteorder(tp, &misc_ctrl_reg);
+	if (err)
+		return err;
+
 	tp->misc_host_ctrl |= (misc_ctrl_reg &
 			       MISC_HOST_CTRL_CHIPREV);
 	pci_write_config_dword(tp->pdev, TG3PCI_MISC_HOST_CTRL,
-- 
2.43.0