1 files changed, 32 insertions, 17 deletions

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index f12d117f44e0..53a1fa306e1e 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/math.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/pci.h>
@@ -350,29 +351,43 @@ static u32 calc_l1ss_pwron(struct pci_dev *pdev, u32 scale, u32 val)
 	return 0;
 }
 
+/*
+ * Encode an LTR_L1.2_THRESHOLD value for the L1 PM Substates Control 1
+ * register.  Ports enter L1.2 when the most recent LTR value is greater
+ * than or equal to LTR_L1.2_THRESHOLD, so we round up to make sure we
+ * don't enter L1.2 too aggressively.
+ *
+ * See PCIe r6.0, sec 5.5.1, 6.18, 7.8.3.3.
+ */
 static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
 {
-	u32 threshold_ns = threshold_us * 1000;
+	u64 threshold_ns = (u64) threshold_us * 1000;
 
-	/* See PCIe r3.1, sec 7.33.3 and sec 6.18 */
-	if (threshold_ns < 32) {
-		*scale = 0;
+	/*
+	 * LTR_L1.2_THRESHOLD_Value ("value") is a 10-bit field with max
+	 * value of 0x3ff.
+	 */
+	if (threshold_ns <= 0x3ff * 1) {
+		*scale = 0;		/* Value times 1ns */
 		*value = threshold_ns;
-	} else if (threshold_ns < 1024) {
-		*scale = 1;
-		*value = threshold_ns >> 5;
-	} else if (threshold_ns < 32768) {
-		*scale = 2;
-		*value = threshold_ns >> 10;
-	} else if (threshold_ns < 1048576) {
-		*scale = 3;
-		*value = threshold_ns >> 15;
-	} else if (threshold_ns < 33554432) {
-		*scale = 4;
-		*value = threshold_ns >> 20;
+	} else if (threshold_ns <= 0x3ff * 32) {
+		*scale = 1;		/* Value times 32ns */
+		*value = roundup(threshold_ns, 32) / 32;
+	} else if (threshold_ns <= 0x3ff * 1024) {
+		*scale = 2;		/* Value times 1024ns */
+		*value = roundup(threshold_ns, 1024) / 1024;
+	} else if (threshold_ns <= 0x3ff * 32768) {
+		*scale = 3;		/* Value times 32768ns */
+		*value = roundup(threshold_ns, 32768) / 32768;
+	} else if (threshold_ns <= 0x3ff * 1048576) {
+		*scale = 4;		/* Value times 1048576ns */
+		*value = roundup(threshold_ns, 1048576) / 1048576;
+	} else if (threshold_ns <= 0x3ff * (u64) 33554432) {
+		*scale = 5;		/* Value times 33554432ns */
+		*value = roundup(threshold_ns, 33554432) / 33554432;
 	} else {
 		*scale = 5;
-		*value = threshold_ns >> 25;
+		*value = 0x3ff;		/* Max representable value */
 	}
 }