[PATCH 10/23] IB/hfi1: Add special setting for low power AOC

Dennis Dalessandro
2016-12-08T03:33:13Z

From: Dean Luick <dean.luick-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

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-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Dean Luick <dean.luick-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
drivers/infiniband/hw/hfi1/platform.c | 44 ++++++++++++++++++++++++++++++++-
1 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/platform.c b/drivers/infiniband/hw/hfi1/platform.c
index 0e70438..838fe84 100644
--- 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");