igc: Add initial LTR support

The LTR message on the PCIe inform the requested latency
on which the PCIe must become active to the downstream
PCIe port of the system.
This patch provide recommended LTR parameters by i225
specification.

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

1 files changed, 100 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/igc/igc_i225.c b/drivers/net/ethernet/intel/igc/igc_i225.c
index 3a4e982edb67..8b67d9b49a83 100644
--- a/drivers/net/ethernet/intel/igc/igc_i225.c
+++ b/drivers/net/ethernet/intel/igc/igc_i225.c
@@ -544,3 +544,103 @@ s32 igc_set_eee_i225(struct igc_hw *hw, bool adv2p5G, bool adv1G,
 
 	return IGC_SUCCESS;
 }
+
+/* igc_set_ltr_i225 - Set Latency Tolerance Reporting thresholds
+ * @hw: pointer to the HW structure
+ * @link: bool indicating link status
+ *
+ * Set the LTR thresholds based on the link speed (Mbps), EEE, and DMAC
+ * settings, otherwise specify that there is no LTR requirement.
+ */
+s32 igc_set_ltr_i225(struct igc_hw *hw, bool link)
+{
+	u32 tw_system, ltrc, ltrv, ltr_min, ltr_max, scale_min, scale_max;
+	u16 speed, duplex;
+	s32 size;
+
+	/* If we do not have link, LTR thresholds are zero. */
+	if (link) {
+		hw->mac.ops.get_speed_and_duplex(hw, &speed, &duplex);
+
+		/* Check if using copper interface with EEE enabled or if the
+		 * link speed is 10 Mbps.
+		 */
+		if (hw->dev_spec._base.eee_enable &&
+		    speed != SPEED_10) {
+			/* EEE enabled, so send LTRMAX threshold. */
+			ltrc = rd32(IGC_LTRC) |
+			       IGC_LTRC_EEEMS_EN;
+			wr32(IGC_LTRC, ltrc);
+
+			/* Calculate tw_system (nsec). */
+			if (speed == SPEED_100) {
+				tw_system = ((rd32(IGC_EEE_SU) &
+					     IGC_TW_SYSTEM_100_MASK) >>
+					     IGC_TW_SYSTEM_100_SHIFT) * 500;
+			} else {
+				tw_system = (rd32(IGC_EEE_SU) &
+					     IGC_TW_SYSTEM_1000_MASK) * 500;
+			}
+		} else {
+			tw_system = 0;
+		}
+
+		/* Get the Rx packet buffer size. */
+		size = rd32(IGC_RXPBS) &
+		       IGC_RXPBS_SIZE_I225_MASK;
+
+		/* Calculations vary based on DMAC settings. */
+		if (rd32(IGC_DMACR) & IGC_DMACR_DMAC_EN) {
+			size -= (rd32(IGC_DMACR) &
+				 IGC_DMACR_DMACTHR_MASK) >>
+				 IGC_DMACR_DMACTHR_SHIFT;
+			/* Convert size to bits. */
+			size *= 1024 * 8;
+		} else {
+			/* Convert size to bytes, subtract the MTU, and then
+			 * convert the size to bits.
+			 */
+			size *= 1024;
+			size *= 8;
+		}
+
+		if (size < 0) {
+			hw_dbg("Invalid effective Rx buffer size %d\n",
+			       size);
+			return -IGC_ERR_CONFIG;
+		}
+
+		/* Calculate the thresholds. Since speed is in Mbps, simplify
+		 * the calculation by multiplying size/speed by 1000 for result
+		 * to be in nsec before dividing by the scale in nsec. Set the
+		 * scale such that the LTR threshold fits in the register.
+		 */
+		ltr_min = (1000 * size) / speed;
+		ltr_max = ltr_min + tw_system;
+		scale_min = (ltr_min / 1024) < 1024 ? IGC_LTRMINV_SCALE_1024 :
+			    IGC_LTRMINV_SCALE_32768;
+		scale_max = (ltr_max / 1024) < 1024 ? IGC_LTRMAXV_SCALE_1024 :
+			    IGC_LTRMAXV_SCALE_32768;
+		ltr_min /= scale_min == IGC_LTRMINV_SCALE_1024 ? 1024 : 32768;
+		ltr_min -= 1;
+		ltr_max /= scale_max == IGC_LTRMAXV_SCALE_1024 ? 1024 : 32768;
+		ltr_max -= 1;
+
+		/* Only write the LTR thresholds if they differ from before. */
+		ltrv = rd32(IGC_LTRMINV);
+		if (ltr_min != (ltrv & IGC_LTRMINV_LTRV_MASK)) {
+			ltrv = IGC_LTRMINV_LSNP_REQ | ltr_min |
+			       (scale_min << IGC_LTRMINV_SCALE_SHIFT);
+			wr32(IGC_LTRMINV, ltrv);
+		}
+
+		ltrv = rd32(IGC_LTRMAXV);
+		if (ltr_max != (ltrv & IGC_LTRMAXV_LTRV_MASK)) {
+			ltrv = IGC_LTRMAXV_LSNP_REQ | ltr_max |
+			       (scale_min << IGC_LTRMAXV_SCALE_SHIFT);
+			wr32(IGC_LTRMAXV, ltrv);
+		}
+	}
+
+	return IGC_SUCCESS;
+}