IB/hfi1: Add special setting for low power AOC

Low power QSFP AOC cables require a different SerDes
Tx PLL bandwidth setting than the default.  The
8051 firmware does not know the details, so the driver
needs to tell the firmware through a special setting.

Reviewed-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/hw/hfi1/platform.c b/drivers/infiniband/hw/hfi1/platform.c
index 0e70438..838fe84 100644 (file)
--- a/drivers/infiniband/hw/hfi1/platform.c
+++ b/drivers/infiniband/hw/hfi1/platform.c
@@ -637,6 +637,38 @@ static void apply_tx_lanes(struct hfi1_pportdata *ppd, u8 field_id,
        }
 }
 
+/*
+ * Return a special SerDes setting for low power AOC cables.  The power class
+ * threshold and setting being used were all found by empirical testing.
+ *
+ * Summary of the logic:
+ *
+ * if (QSFP and QSFP_TYPE == AOC and QSFP_POWER_CLASS < 4)
+ *     return 0xe
+ * return 0; // leave at default
+ */
+static u8 aoc_low_power_setting(struct hfi1_pportdata *ppd)
+{
+       u8 *cache = ppd->qsfp_info.cache;
+       int power_class;
+
+       /* QSFP only */
+       if (ppd->port_type != PORT_TYPE_QSFP)
+               return 0; /* leave at default */
+
+       /* active optical cables only */
+       switch ((cache[QSFP_MOD_TECH_OFFS] & 0xF0) >> 4) {
+       case 0x0 ... 0x9: /* fallthrough */
+       case 0xC: /* fallthrough */
+       case 0xE:
+               /* active AOC */
+               power_class = get_qsfp_power_class(cache[QSFP_MOD_PWR_OFFS]);
+               if (power_class < QSFP_POWER_CLASS_4)
+                       return 0xe;
+       }
+       return 0; /* leave at default */
+}
+
 static void apply_tunings(
                struct hfi1_pportdata *ppd, u32 tx_preset_index,
                u8 tuning_method, u32 total_atten, u8 limiting_active)
@@ -705,7 +737,17 @@ static void apply_tunings(
                tx_preset_index, TX_PRESET_TABLE_POSTCUR, &tx_preset, 4);
        postcur = tx_preset;
 
-       config_data = precur | (attn << 8) | (postcur << 16);
+       /*
+        * NOTES:
+        * o The aoc_low_power_setting is applied to all lanes even
+        *   though only lane 0's value is examined by the firmware.
+        * o A lingering low power setting after a cable swap does
+        *   not occur.  On cable unplug the 8051 is reset and
+        *   restarted on cable insert.  This resets all settings to
+        *   their default, erasing any previous low power setting.
+        */
+       config_data = precur | (attn << 8) | (postcur << 16) |
+                       (aoc_low_power_setting(ppd) << 24);
 
        apply_tx_lanes(ppd, TX_EQ_SETTINGS, config_data,
                       "Applying TX settings");