PCI/ASPM: Add support for L1 substates

Add support for ASPM L1 substates.  For details about L1 substates, see the
PCIe r3.1 spec, which includes the ECN below in secs 5.5 and 7.33.

Add macros for the 4 new L1 substates, and add a new ASPM "POWER_SUPERSAVE"
policy that can be used to enable L1 substates on a system if desired.  The
new policy is in a sense, a superset of the existing POWERSAVE policy.  The
4 policies are now:

  DEFAULT: Reads and uses whatever ASPM states BIOS enabled
  PERFORMANCE: Everything except L0 disabled.
  POWERSAVE: L0s and L1 enabled (but not L1 substates)
  POWER_SUPERSAVE: L0s + L1 + L1 substates also enabled

[bhelgaas: add PCIe r3.1 spec reference]
Link: https://pcisig.com/sites/default/files/specification_documents/ECN_L1_PM_Substates_with_CLKREQ_31_May_2013_Rev10a.pdf
Signed-off-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/Kconfig

@@ -71,6 +71,14 @@ config PCIEASPM_POWERSAVE
 	  Enable PCI Express ASPM L0s and L1 where possible, even if the
 	  BIOS did not.
 
+config PCIEASPM_POWER_SUPERSAVE
+	bool "Power Supersave"
+	depends on PCIEASPM
+	help
+	  Same as PCIEASPM_POWERSAVE, except it also enables L1 substates where
+	  possible. This would result in higher power savings while staying in L1
+	  where the components support it.
+
 config PCIEASPM_PERFORMANCE
 	bool "Performance"
 	depends on PCIEASPM

drivers/pci/pcie/aspm.c

@@ -30,8 +30,17 @@
 #define ASPM_STATE_L0S_UP	(1)	/* Upstream direction L0s state */
 #define ASPM_STATE_L0S_DW	(2)	/* Downstream direction L0s state */
 #define ASPM_STATE_L1		(4)	/* L1 state */
+#define ASPM_STATE_L1_1		(8)	/* ASPM L1.1 state */
+#define ASPM_STATE_L1_2		(0x10)	/* ASPM L1.2 state */
+#define ASPM_STATE_L1_1_PCIPM	(0x20)	/* PCI PM L1.1 state */
+#define ASPM_STATE_L1_2_PCIPM	(0x40)	/* PCI PM L1.2 state */
+#define ASPM_STATE_L1_SS_PCIPM	(ASPM_STATE_L1_1_PCIPM | ASPM_STATE_L1_2_PCIPM)
+#define ASPM_STATE_L1_2_MASK	(ASPM_STATE_L1_2 | ASPM_STATE_L1_2_PCIPM)
+#define ASPM_STATE_L1SS		(ASPM_STATE_L1_1 | ASPM_STATE_L1_1_PCIPM |\
+				 ASPM_STATE_L1_2_MASK)
 #define ASPM_STATE_L0S		(ASPM_STATE_L0S_UP | ASPM_STATE_L0S_DW)
-#define ASPM_STATE_ALL		(ASPM_STATE_L0S | ASPM_STATE_L1)
+#define ASPM_STATE_ALL		(ASPM_STATE_L0S | ASPM_STATE_L1 |	\
+				 ASPM_STATE_L1SS)
 
 struct aspm_latency {
 	u32 l0s;			/* L0s latency (nsec) */
@@ -47,11 +56,11 @@ struct pcie_link_state {
 	struct list_head link;		/* node in parent's children list */
 
 	/* ASPM state */
-	u32 aspm_support:3;		/* Supported ASPM state */
-	u32 aspm_enabled:3;		/* Enabled ASPM state */
-	u32 aspm_capable:3;		/* Capable ASPM state with latency */
-	u32 aspm_default:3;		/* Default ASPM state by BIOS */
-	u32 aspm_disable:3;		/* Disabled ASPM state */
+	u32 aspm_support:7;		/* Supported ASPM state */
+	u32 aspm_enabled:7;		/* Enabled ASPM state */
+	u32 aspm_capable:7;		/* Capable ASPM state with latency */
+	u32 aspm_default:7;		/* Default ASPM state by BIOS */
+	u32 aspm_disable:7;		/* Disabled ASPM state */
 
 	/* Clock PM state */
 	u32 clkpm_capable:1;		/* Clock PM capable? */
@@ -76,11 +85,14 @@ static LIST_HEAD(link_list);
 #define POLICY_DEFAULT 0	/* BIOS default setting */
 #define POLICY_PERFORMANCE 1	/* high performance */
 #define POLICY_POWERSAVE 2	/* high power saving */
+#define POLICY_POWER_SUPERSAVE 3 /* possibly even more power saving */
 
 #ifdef CONFIG_PCIEASPM_PERFORMANCE
 static int aspm_policy = POLICY_PERFORMANCE;
 #elif defined CONFIG_PCIEASPM_POWERSAVE
 static int aspm_policy = POLICY_POWERSAVE;
+#elif defined CONFIG_PCIEASPM_POWER_SUPERSAVE
+static int aspm_policy = POLICY_POWER_SUPERSAVE;
 #else
 static int aspm_policy;
 #endif
@@ -88,7 +100,8 @@ static int aspm_policy;
 static const char *policy_str[] = {
 	[POLICY_DEFAULT] = "default",
 	[POLICY_PERFORMANCE] = "performance",
-	[POLICY_POWERSAVE] = "powersave"
+	[POLICY_POWERSAVE] = "powersave",
+	[POLICY_POWER_SUPERSAVE] = "powersupersave"
 };
 
 #define LINK_RETRAIN_TIMEOUT HZ
@@ -101,6 +114,9 @@ static int policy_to_aspm_state(struct pcie_link_state *link)
 		return 0;
 	case POLICY_POWERSAVE:
 		/* Enable ASPM L0s/L1 */
+		return (ASPM_STATE_L0S | ASPM_STATE_L1);
+	case POLICY_POWER_SUPERSAVE:
+		/* Enable Everything */
 		return ASPM_STATE_ALL;
 	case POLICY_DEFAULT:
 		return link->aspm_default;
@@ -115,7 +131,8 @@ static int policy_to_clkpm_state(struct pcie_link_state *link)
 		/* Disable ASPM and Clock PM */
 		return 0;
 	case POLICY_POWERSAVE:
-		/* Disable Clock PM */
+	case POLICY_POWER_SUPERSAVE:
+		/* Enable Clock PM */
 		return 1;
 	case POLICY_DEFAULT:
 		return link->clkpm_default;
@@ -612,7 +629,8 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 	 * the BIOS's expectation, we'll do so once pci_enable_device() is
 	 * called.
 	 */
-	if (aspm_policy != POLICY_POWERSAVE) {
+	if (aspm_policy != POLICY_POWERSAVE &&
+	    aspm_policy != POLICY_POWER_SUPERSAVE) {
 		pcie_config_aspm_path(link);
 		pcie_set_clkpm(link, policy_to_clkpm_state(link));
 	}
@@ -712,7 +730,8 @@ void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
 	if (aspm_disabled || !link)
 		return;
 
-	if (aspm_policy != POLICY_POWERSAVE)
+	if (aspm_policy != POLICY_POWERSAVE &&
+	    aspm_policy != POLICY_POWER_SUPERSAVE)
 		return;
 
 	down_read(&pci_bus_sem);