ath9k: add comments for ath9k_hw_configpcipowersave()

This is used for ASPM.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath9k/hw.c b/drivers/net/wireless/ath9k/hw.c
index 72ca1c8ff090..cfcaaf886d03 100644
--- a/drivers/net/wireless/ath9k/hw.c
+++ b/drivers/net/wireless/ath9k/hw.c
@@ -2632,6 +2632,15 @@ bool ath9k_hw_setpower(struct ath_hw *ah, enum ath9k_power_mode mode)
         return status;
 }
 
+/*
+ * Helper for ASPM support.
+ *
+ * Disable PLL when in L0s as well as receiver clock when in L1.
+ * This power saving option must be enabled through the SerDes.
+ *
+ * Programming the SerDes must go through the same 288 bit serial shift
+ * register as the other analog registers.  Hence the 9 writes.
+ */
 void ath9k_hw_configpcipowersave(struct ath_hw *ah, int restore)
 {
         u8 i;
@@ -2639,13 +2648,20 @@ void ath9k_hw_configpcipowersave(struct ath_hw *ah, int restore)
         if (ah->is_pciexpress != true)
                 return;
 
+        /* Do not touch SerDes registers */
         if (ah->config.pcie_powersave_enable == 2)
                 return;
 
+        /* Nothing to do on restore for 11N */
         if (restore)
                 return;
 
         if (AR_SREV_9280_20_OR_LATER(ah)) {
+                /*
+                 * AR9280 2.0 or later chips use SerDes values from the
+                 * initvals.h initialized depending on chipset during
+                 * ath9k_hw_do_attach()
+                 */
                 for (i = 0; i < ah->iniPcieSerdes.ia_rows; i++) {
                         REG_WRITE(ah, INI_RA(&ah->iniPcieSerdes, i, 0),
                                   INI_RA(&ah->iniPcieSerdes, i, 1));
@@ -2656,10 +2672,12 @@ void ath9k_hw_configpcipowersave(struct ath_hw *ah, int restore)
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x9248fd00);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x24924924);
 
+                /* RX shut off when elecidle is asserted */
                 REG_WRITE(ah, AR_PCIE_SERDES, 0xa8000019);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x13160820);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0xe5980560);
 
+                /* Shut off CLKREQ active in L1 */
                 if (ah->config.pcie_clock_req)
                         REG_WRITE(ah, AR_PCIE_SERDES, 0x401deffc);
                 else
@@ -2669,29 +2687,46 @@ void ath9k_hw_configpcipowersave(struct ath_hw *ah, int restore)
                 REG_WRITE(ah, AR_PCIE_SERDES, 0xbe105554);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x00043007);
 
+                /* Load the new settings */
                 REG_WRITE(ah, AR_PCIE_SERDES2, 0x00000000);
 
                 udelay(1000);
         } else {
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x9248fc00);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x24924924);
+
+                /* RX shut off when elecidle is asserted */
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x28000039);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x53160824);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0xe5980579);
+
+                /*
+                 * Ignore ah->ah_config.pcie_clock_req setting for
+                 * pre-AR9280 11n
+                 */
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x001defff);
+
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x1aaabe40);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0xbe105554);
                 REG_WRITE(ah, AR_PCIE_SERDES, 0x000e3007);
+
+                /* Load the new settings */
                 REG_WRITE(ah, AR_PCIE_SERDES2, 0x00000000);
         }
 
+        /* set bit 19 to allow forcing of pcie core into L1 state */
         REG_SET_BIT(ah, AR_PCIE_PM_CTRL, AR_PCIE_PM_CTRL_ENA);
 
+        /* Several PCIe massages to ensure proper behaviour */
         if (ah->config.pcie_waen) {
                 REG_WRITE(ah, AR_WA, ah->config.pcie_waen);
         } else {
                 if (AR_SREV_9285(ah))
                         REG_WRITE(ah, AR_WA, AR9285_WA_DEFAULT);
+                /*
+                 * On AR9280 chips bit 22 of 0x4004 needs to be set to
+                 * otherwise card may disappear.
+                 */
                 else if (AR_SREV_9280(ah))
                         REG_WRITE(ah, AR_WA, AR9280_WA_DEFAULT);
                 else