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