[PATCH net] net: thunderx: workaround BGX TX Underflow issue

[Robert Jones]

From: Tim Harvey <tharvey@xxxxxxxxxxxxx>

While it is not yet understood why a TX underflow can easily occur
for SGMII interfaces resulting in a TX wedge. It has been found that
disabling/re-enabling the LMAC resolves the issue.

Signed-off-by: Tim Harvey <tharvey@xxxxxxxxxxxxx>
Reviewed-by: Robert Jones <rjones@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/cavium/thunder/thunder_bgx.c | 54 +++++++++++++++++++++++
 drivers/net/ethernet/cavium/thunder/thunder_bgx.h |  9 ++++
 2 files changed, 63 insertions(+)

diff --git a/drivers/net/ethernet/cavium/thunder/thunder_bgx.c b/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
index c4f6ec0..078ecea 100644
--- a/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
+++ b/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
@@ -74,6 +74,7 @@ struct bgx {
 	struct pci_dev		*pdev;
 	bool                    is_dlm;
 	bool                    is_rgx;
+	char			irq_name[7];
 };

 static struct bgx *bgx_vnic[MAX_BGX_THUNDER];
@@ -1535,6 +1536,53 @@ static int bgx_init_phy(struct bgx *bgx)
 	return bgx_init_of_phy(bgx);
 }

+static irqreturn_t bgx_intr_handler(int irq, void *data)
+{
+	struct bgx *bgx = (struct bgx *)data;
+	struct device *dev = &bgx->pdev->dev;
+	u64 status, val;
+	int lmac;
+
+	for (lmac = 0; lmac < bgx->lmac_count; lmac++) {
+		status = bgx_reg_read(bgx, lmac, BGX_GMP_GMI_TXX_INT);
+		if (status & GMI_TXX_INT_UNDFLW) {
+			dev_err(dev, "BGX%d lmac%d UNDFLW\n", bgx->bgx_id,
+				lmac);
+			val = bgx_reg_read(bgx, lmac, BGX_CMRX_CFG);
+			val &= ~CMR_EN;
+			bgx_reg_write(bgx, lmac, BGX_CMRX_CFG, val);
+			val |= CMR_EN;
+			bgx_reg_write(bgx, lmac, BGX_CMRX_CFG, val);
+		}
+		/* clear interrupts */
+		bgx_reg_write(bgx, lmac, BGX_GMP_GMI_TXX_INT, status);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int bgx_register_intr(struct pci_dev *pdev)
+{
+	struct bgx *bgx = pci_get_drvdata(pdev);
+	struct device *dev = &pdev->dev;
+	int num_vec, ret;
+
+	/* Enable MSI-X */
+	num_vec = pci_msix_vec_count(pdev);
+	ret = pci_alloc_irq_vectors(pdev, num_vec, num_vec, PCI_IRQ_MSIX);
+	if (ret < 0) {
+		dev_err(dev, "Req for #%d msix vectors failed\n", num_vec);
+		return 1;
+	}
+	sprintf(bgx->irq_name, "BGX%d", bgx->bgx_id);
+	ret = request_irq(pci_irq_vector(pdev, GMPX_GMI_TX_INT),
+		bgx_intr_handler, 0, bgx->irq_name, bgx);
+	if (ret)
+		return 1;
+
+	return 0;
+}
+
 static int bgx_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	int err;
@@ -1604,6 +1652,8 @@ static int bgx_probe(struct pci_dev *pdev, const struct pci_device_id *ent)

 	bgx_init_hw(bgx);

+	bgx_register_intr(pdev);
+
 	/* Enable all LMACs */
 	for (lmac = 0; lmac < bgx->lmac_count; lmac++) {
 		err = bgx_lmac_enable(bgx, lmac);
@@ -1614,6 +1664,10 @@ static int bgx_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 				bgx_lmac_disable(bgx, --lmac);
 			goto err_enable;
 		}
+
+		/* enable TX FIFO Underflow interrupt */
+		bgx_reg_modify(bgx, lmac, BGX_GMP_GMI_TXX_INT_ENA_W1S,
+			       GMI_TXX_INT_UNDFLW);
 	}

 	return 0;
diff --git a/drivers/net/ethernet/cavium/thunder/thunder_bgx.h b/drivers/net/ethernet/cavium/thunder/thunder_bgx.h
index 2588870..cdea493 100644
--- a/drivers/net/ethernet/cavium/thunder/thunder_bgx.h
+++ b/drivers/net/ethernet/cavium/thunder/thunder_bgx.h
@@ -180,6 +180,15 @@
 #define BGX_GMP_GMI_TXX_BURST		0x38228
 #define BGX_GMP_GMI_TXX_MIN_PKT		0x38240
 #define BGX_GMP_GMI_TXX_SGMII_CTL	0x38300
+#define BGX_GMP_GMI_TXX_INT		0x38500
+#define BGX_GMP_GMI_TXX_INT_W1S		0x38508
+#define BGX_GMP_GMI_TXX_INT_ENA_W1C	0x38510
+#define BGX_GMP_GMI_TXX_INT_ENA_W1S	0x38518
+#define  GMI_TXX_INT_PTP_LOST			BIT_ULL(4)
+#define  GMI_TXX_INT_LATE_COL			BIT_ULL(3)
+#define  GMI_TXX_INT_XSDEF			BIT_ULL(2)
+#define  GMI_TXX_INT_XSCOL			BIT_ULL(1)
+#define  GMI_TXX_INT_UNDFLW			BIT_ULL(0)

 #define BGX_MSIX_VEC_0_29_ADDR		0x400000 /* +(0..29) << 4 */
 #define BGX_MSIX_VEC_0_29_CTL		0x400008
--
2.9.2