Merge branch 'pci/aspm' into next

* pci/aspm:
  PCI/ASPM: Unexport internal ASPM interfaces
  PCI/ASPM: Enable Latency Tolerance Reporting when supported
  PCI/ASPM: Calculate LTR_L1.2_THRESHOLD from device characteristics

1 files changed, 47 insertions, 24 deletions

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 9783e10da3a9..3b9b4d50cd98 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -43,18 +43,6 @@
 #define ASPM_STATE_ALL		(ASPM_STATE_L0S | ASPM_STATE_L1 |	\
 				 ASPM_STATE_L1SS)
 
-/*
- * When L1 substates are enabled, the LTR L1.2 threshold is a timing parameter
- * that decides whether L1.1 or L1.2 is entered (Refer PCIe spec for details).
- * Not sure is there is a way to "calculate" this on the fly, but maybe we
- * could turn it into a parameter in future.  This value has been taken from
- * the following files from Intel's coreboot (which is the only code I found
- * to have used this):
- * https://www.coreboot.org/pipermail/coreboot-gerrit/2015-March/021134.html
- * https://review.coreboot.org/#/c/8832/
- */
-#define LTR_L1_2_THRESHOLD_BITS	((1 << 21) | (1 << 23) | (1 << 30))
-
 struct aspm_latency {
 	u32 l0s;			/* L0s latency (nsec) */
 	u32 l1;				/* L1 latency (nsec) */
@@ -333,6 +321,32 @@ static u32 calc_l1ss_pwron(struct pci_dev *pdev, u32 scale, u32 val)
 	return 0;
 }
 
+static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
+{
+	u64 threshold_ns = threshold_us * 1000;
+
+	/* See PCIe r3.1, sec 7.33.3 and sec 6.18 */
+	if (threshold_ns < 32) {
+		*scale = 0;
+		*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 {
+		*scale = 5;
+		*value = threshold_ns >> 25;
+	}
+}
+
 struct aspm_register_info {
 	u32 support:2;
 	u32 enabled:2;
@@ -443,6 +457,7 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 				struct aspm_register_info *dwreg)
 {
 	u32 val1, val2, scale1, scale2;
+	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
 
 	link->l1ss.up_cap_ptr = upreg->l1ss_cap_ptr;
 	link->l1ss.dw_cap_ptr = dwreg->l1ss_cap_ptr;
@@ -454,16 +469,7 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	/* Choose the greater of the two Port Common_Mode_Restore_Times */
 	val1 = (upreg->l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
 	val2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
-	if (val1 > val2)
-		link->l1ss.ctl1 |= val1 << 8;
-	else
-		link->l1ss.ctl1 |= val2 << 8;
-
-	/*
-	 * We currently use LTR L1.2 threshold to be fixed constant picked from
-	 * Intel's coreboot.
-	 */
-	link->l1ss.ctl1 |= LTR_L1_2_THRESHOLD_BITS;
+	t_common_mode = max(val1, val2);
 
 	/* Choose the greater of the two Port T_POWER_ON times */
 	val1   = (upreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_VALUE) >> 19;
@@ -472,10 +478,27 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	scale2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_SCALE) >> 16;
 
 	if (calc_l1ss_pwron(link->pdev, scale1, val1) >
-	    calc_l1ss_pwron(link->downstream, scale2, val2))
+	    calc_l1ss_pwron(link->downstream, scale2, val2)) {
 		link->l1ss.ctl2 |= scale1 | (val1 << 3);
-	else
+		t_power_on = calc_l1ss_pwron(link->pdev, scale1, val1);
+	} else {
 		link->l1ss.ctl2 |= scale2 | (val2 << 3);
+		t_power_on = calc_l1ss_pwron(link->downstream, scale2, val2);
+	}
+
+	/*
+	 * Set LTR_L1.2_THRESHOLD to the time required to transition the
+	 * Link from L0 to L1.2 and back to L0 so we enter L1.2 only if
+	 * downstream devices report (via LTR) that they can tolerate at
+	 * least that much latency.
+	 *
+	 * Based on PCIe r3.1, sec 5.5.3.3.1, Figures 5-16 and 5-17, and
+	 * Table 5-11.  T(POWER_OFF) is at most 2us and T(L1.2) is at
+	 * least 4us.
+	 */
+	l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
+	encode_l12_threshold(l1_2_threshold, &scale, &value);
+	link->l1ss.ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
 }
 
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)