ntb: intel: add Intel NTB LTR vendor support for gen4 NTB

Intel NTB device has custom LTR management that is not compliant with the
PCIe standard. Add support to set LTR status triggered by link status
change.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/hw/intel/ntb_hw_gen1.h

@@ -141,6 +141,7 @@
 #define NTB_HWERR_B2BDOORBELL_BIT14	BIT_ULL(2)
 #define NTB_HWERR_MSIX_VECTOR32_BAD	BIT_ULL(3)
 #define NTB_HWERR_BAR_ALIGN		BIT_ULL(4)
+#define NTB_HWERR_LTR_BAD		BIT_ULL(5)
 
 extern struct intel_b2b_addr xeon_b2b_usd_addr;
 extern struct intel_b2b_addr xeon_b2b_dsd_addr;

drivers/ntb/hw/intel/ntb_hw_gen4.c

@@ -177,8 +177,10 @@ int gen4_init_dev(struct intel_ntb_dev *ndev)
 
 	ndev->reg = &gen4_reg;
 
-	if (pdev_is_ICX(pdev))
+	if (pdev_is_ICX(pdev)) {
 		ndev->hwerr_flags |= NTB_HWERR_BAR_ALIGN;
+		ndev->hwerr_flags |= NTB_HWERR_LTR_BAD;
+	}
 
 	ppd1 = ioread32(ndev->self_mmio + GEN4_PPD1_OFFSET);
 	ndev->ntb.topo = gen4_ppd_topo(ndev, ppd1);
@@ -431,6 +433,25 @@ static int intel_ntb4_link_enable(struct ntb_dev *ntb,
 		dev_dbg(&ntb->pdev->dev,
 				"ignoring max_width %d\n", max_width);
 
+	if (!(ndev->hwerr_flags & NTB_HWERR_LTR_BAD)) {
+		u32 ltr;
+
+		/* Setup active snoop LTR values */
+		ltr = NTB_LTR_ACTIVE_REQMNT | NTB_LTR_ACTIVE_VAL | NTB_LTR_ACTIVE_LATSCALE;
+		/* Setup active non-snoop values */
+		ltr = (ltr << NTB_LTR_NS_SHIFT) | ltr;
+		iowrite32(ltr, ndev->self_mmio + GEN4_LTR_ACTIVE_OFFSET);
+
+		/* Setup idle snoop LTR values */
+		ltr = NTB_LTR_IDLE_VAL | NTB_LTR_IDLE_LATSCALE | NTB_LTR_IDLE_REQMNT;
+		/* Setup idle non-snoop values */
+		ltr = (ltr << NTB_LTR_NS_SHIFT) | ltr;
+		iowrite32(ltr, ndev->self_mmio + GEN4_LTR_IDLE_OFFSET);
+
+		/* setup PCIe LTR to active */
+		iowrite8(NTB_LTR_SWSEL_ACTIVE, ndev->self_mmio + GEN4_LTR_SWSEL_OFFSET);
+	}
+
 	ntb_ctl = NTB_CTL_E2I_BAR23_SNOOP | NTB_CTL_I2E_BAR23_SNOOP;
 	ntb_ctl |= NTB_CTL_E2I_BAR45_SNOOP | NTB_CTL_I2E_BAR45_SNOOP;
 	iowrite32(ntb_ctl, ndev->self_mmio + ndev->reg->ntb_ctl);
@@ -476,6 +497,10 @@ static int intel_ntb4_link_disable(struct ntb_dev *ntb)
 	lnkctl |= GEN4_LINK_CTRL_LINK_DISABLE;
 	iowrite16(lnkctl, ndev->self_mmio + GEN4_LINK_CTRL_OFFSET);
 
+	/* set LTR to idle */
+	if (!(ndev->hwerr_flags & NTB_HWERR_LTR_BAD))
+		iowrite8(NTB_LTR_SWSEL_IDLE, ndev->self_mmio + GEN4_LTR_SWSEL_OFFSET);
+
 	ndev->dev_up = 0;
 
 	return 0;

drivers/ntb/hw/intel/ntb_hw_gen4.h

@@ -35,6 +35,9 @@
 #define GEN4_IM_SPAD_SEM_OFFSET		0x00c0	/* SPAD hw semaphore */
 #define GEN4_IM_SPAD_STICKY_OFFSET	0x00c4  /* sticky SPAD */
 #define GEN4_IM_DOORBELL_OFFSET		0x0100  /* 0-31 doorbells */
+#define GEN4_LTR_SWSEL_OFFSET		0x30ec
+#define GEN4_LTR_ACTIVE_OFFSET		0x30f0
+#define GEN4_LTR_IDLE_OFFSET		0x30f4
 #define GEN4_EM_SPAD_OFFSET		0x8080
 /* note, link status is now in MMIO and not config space for NTB */
 #define GEN4_LINK_CTRL_OFFSET		0xb050
@@ -80,6 +83,18 @@
 
 #define NTB_SJC_FORCEDETECT		0x000004
 
+#define NTB_LTR_SWSEL_ACTIVE		0x0
+#define NTB_LTR_SWSEL_IDLE		0x1
+
+#define NTB_LTR_NS_SHIFT		16
+#define NTB_LTR_ACTIVE_VAL		0x0000  /* 0 us */
+#define NTB_LTR_ACTIVE_LATSCALE		0x0800  /* 1us scale */
+#define NTB_LTR_ACTIVE_REQMNT		0x8000  /* snoop req enable */
+
+#define NTB_LTR_IDLE_VAL		0x0258  /* 600 us */
+#define NTB_LTR_IDLE_LATSCALE		0x0800  /* 1us scale */
+#define NTB_LTR_IDLE_REQMNT		0x8000  /* snoop req enable */
+
 ssize_t ndev_ntb4_debugfs_read(struct file *filp, char __user *ubuf,
 				      size_t count, loff_t *offp);
 int gen4_init_dev(struct intel_ntb_dev *ndev);