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iwlwifi: Document Rx calibration

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Document Rx calibration

Signed-off-by: Ben Cahill <ben.m.cahill@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Ben Cahill 2007-11-29 11:09:51 +08:00 committed by David S. Miller
parent abceddb407
commit f7d09d7c45
3 changed files with 261 additions and 25 deletions
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267
drivers/net/wireless/iwlwifi/iwl-4965-commands.h
View File

@ -1573,25 +1573,278 @@ struct iwl4965_missed_beacon_notif {
__le32 num_recvd_beacons;
} __attribute__ ((packed));
/******************************************************************************
* (11)
* Rx Calibration Commands:
*
* With the uCode used for open source drivers, most Tx calibration (except
* for Tx Power) and most Rx calibration is done by uCode during the
* "initialize" phase of uCode boot. Driver must calibrate only:
*
* 1) Tx power (depends on temperature), described elsewhere
* 2) Receiver gain balance (optimize MIMO, and detect disconnected antennas)
* 3) Receiver sensitivity (to optimize signal detection)
*
*****************************************************************************/
#define PHY_CALIBRATE_DIFF_GAIN_CMD (7)
#define HD_TABLE_SIZE (11)
/**
* SENSITIVITY_CMD = 0xa8 (command, has simple generic response)
*
* This command sets up the Rx signal detector for a sensitivity level that
* is high enough to lock onto all signals within the associated network,
* but low enough to ignore signals that are below a certain threshold, so as
* not to have too many "false alarms". False alarms are signals that the
* Rx DSP tries to lock onto, but then discards after determining that they
* are noise.
*
* The optimum number of false alarms is between 5 and 50 per 200 TUs
* (200 * 1024 uSecs, i.e. 204.8 milliseconds) of actual Rx time (i.e.
* time listening, not transmitting). Driver must adjust sensitivity so that
* the ratio of actual false alarms to actual Rx time falls within this range.
*
* While associated, uCode delivers STATISTICS_NOTIFICATIONs after each
* received beacon. These provide information to the driver to analyze the
* sensitivity. Don't analyze statistics that come in from scanning, or any
* other non-associated-network source. Pertinent statistics include:
*
* From "general" statistics (struct statistics_rx_non_phy):
*
* (beacon_energy_[abc] & 0x0FF00) >> 8 (unsigned, higher value is lower level)
* Measure of energy of desired signal. Used for establishing a level
* below which the device does not detect signals.
*
* (beacon_silence_rssi_[abc] & 0x0FF00) >> 8 (unsigned, units in dB)
* Measure of background noise in silent period after beacon.
*
* channel_load
* uSecs of actual Rx time during beacon period (varies according to
* how much time was spent transmitting).
*
* From "cck" and "ofdm" statistics (struct statistics_rx_phy), separately:
*
* false_alarm_cnt
* Signal locks abandoned early (before phy-level header).
*
* plcp_err
* Signal locks abandoned late (during phy-level header).
*
* NOTE: Both false_alarm_cnt and plcp_err increment monotonically from
* beacon to beacon, i.e. each value is an accumulation of all errors
* before and including the latest beacon. Values will wrap around to 0
* after counting up to 2^32 - 1. Driver must differentiate vs.
* previous beacon's values to determine # false alarms in the current
* beacon period.
*
* Total number of false alarms = false_alarms + plcp_errs
*
* For OFDM, adjust the following table entries in struct iwl_sensitivity_cmd
* (notice that the start points for OFDM are at or close to settings for
* maximum sensitivity):
*
* START / MIN / MAX
* HD_AUTO_CORR32_X1_TH_ADD_MIN_INDEX 90 / 85 / 120
* HD_AUTO_CORR32_X1_TH_ADD_MIN_MRC_INDEX 170 / 170 / 210
* HD_AUTO_CORR32_X4_TH_ADD_MIN_INDEX 105 / 105 / 140
* HD_AUTO_CORR32_X4_TH_ADD_MIN_MRC_INDEX 220 / 220 / 270
*
* If actual rate of OFDM false alarms (+ plcp_errors) is too high
* (greater than 50 for each 204.8 msecs listening), reduce sensitivity
* by *adding* 1 to all 4 of the table entries above, up to the max for
* each entry. Conversely, if false alarm rate is too low (less than 5
* for each 204.8 msecs listening), *subtract* 1 from each entry to
* increase sensitivity.
*
* For CCK sensitivity, keep track of the following:
*
* 1). 20-beacon history of maximum background noise, indicated by
* (beacon_silence_rssi_[abc] & 0x0FF00), units in dB, across the
* 3 receivers. For any given beacon, the "silence reference" is
* the maximum of last 60 samples (20 beacons * 3 receivers).
*
* 2). 10-beacon history of strongest signal level, as indicated
* by (beacon_energy_[abc] & 0x0FF00) >> 8, across the 3 receivers,
* i.e. the strength of the signal through the best receiver at the
* moment. These measurements are "upside down", with lower values
* for stronger signals, so max energy will be *minimum* value.
*
* Then for any given beacon, the driver must determine the *weakest*
* of the strongest signals; this is the minimum level that needs to be
* successfully detected, when using the best receiver at the moment.
* "Max cck energy" is the maximum (higher value means lower energy!)
* of the last 10 minima. Once this is determined, driver must add
* a little margin by adding "6" to it.
*
* 3). Number of consecutive beacon periods with too few false alarms.
* Reset this to 0 at the first beacon period that falls within the
* "good" range (5 to 50 false alarms per 204.8 milliseconds rx).
*
* Then, adjust the following CCK table entries in struct iwl_sensitivity_cmd
* (notice that the start points for CCK are at maximum sensitivity):
*
* START / MIN / MAX
* HD_AUTO_CORR40_X4_TH_ADD_MIN_INDEX 125 / 125 / 200
* HD_AUTO_CORR40_X4_TH_ADD_MIN_MRC_INDEX 200 / 200 / 400
* HD_MIN_ENERGY_CCK_DET_INDEX 100 / 0 / 100
*
* If actual rate of CCK false alarms (+ plcp_errors) is too high
* (greater than 50 for each 204.8 msecs listening), method for reducing
* sensitivity is:
*
* 1) *Add* 3 to value in HD_AUTO_CORR40_X4_TH_ADD_MIN_MRC_INDEX,
* up to max 400.
*
* 2) If current value in HD_AUTO_CORR40_X4_TH_ADD_MIN_INDEX is < 160,
* sensitivity has been reduced a significant amount; bring it up to
* a moderate 161. Otherwise, *add* 3, up to max 200.
*
* 3) a) If current value in HD_AUTO_CORR40_X4_TH_ADD_MIN_INDEX is > 160,
* sensitivity has been reduced only a moderate or small amount;
* *subtract* 2 from value in HD_MIN_ENERGY_CCK_DET_INDEX,
* down to min 0. Otherwise (if gain has been significantly reduced),
* don't change the HD_MIN_ENERGY_CCK_DET_INDEX value.
*
* b) Save a snapshot of the "silence reference".
*
* If actual rate of CCK false alarms (+ plcp_errors) is too low
* (less than 5 for each 204.8 msecs listening), method for increasing
* sensitivity is used only if:
*
* 1a) Previous beacon did not have too many false alarms
* 1b) AND difference between previous "silence reference" and current
* "silence reference" (prev - current) is 2 or more,
* OR 2) 100 or more consecutive beacon periods have had rate of
* less than 5 false alarms per 204.8 milliseconds rx time.
*
* Method for increasing sensitivity:
*
* 1) *Subtract* 3 from value in HD_AUTO_CORR40_X4_TH_ADD_MIN_INDEX,
* down to min 125.
*
* 2) *Subtract* 3 from value in HD_AUTO_CORR40_X4_TH_ADD_MIN_MRC_INDEX,
* down to min 200.
*
* 3) *Add* 2 to value in HD_MIN_ENERGY_CCK_DET_INDEX, up to max 100.
*
* If actual rate of CCK false alarms (+ plcp_errors) is within good range
* (between 5 and 50 for each 204.8 msecs listening):
*
* 1) Save a snapshot of the silence reference.
*
* 2) If previous beacon had too many CCK false alarms (+ plcp_errors),
* give some extra margin to energy threshold by *subtracting* 8
* from value in HD_MIN_ENERGY_CCK_DET_INDEX.
*
* For all cases (too few, too many, good range), make sure that the CCK
* detection threshold (energy) is below the energy level for robust
* detection over the past 10 beacon periods, the "Max cck energy".
* Lower values mean higher energy; this means making sure that the value
* in HD_MIN_ENERGY_CCK_DET_INDEX is at or *above* "Max cck energy".
*
* Driver should set the following entries to fixed values:
*
* HD_MIN_ENERGY_OFDM_DET_INDEX 100
* HD_BARKER_CORR_TH_ADD_MIN_INDEX 190
* HD_BARKER_CORR_TH_ADD_MIN_MRC_INDEX 390
* HD_OFDM_ENERGY_TH_IN_INDEX 62
*/
/*
* Table entries in SENSITIVITY_CMD (struct iwl4965_sensitivity_cmd)
*/
#define HD_TABLE_SIZE (11) /* number of entries */
#define HD_MIN_ENERGY_CCK_DET_INDEX (0) /* table indexes */
#define HD_MIN_ENERGY_OFDM_DET_INDEX (1)
#define HD_AUTO_CORR32_X1_TH_ADD_MIN_INDEX (2)
#define HD_AUTO_CORR32_X1_TH_ADD_MIN_MRC_INDEX (3)
#define HD_AUTO_CORR40_X4_TH_ADD_MIN_MRC_INDEX (4)
#define HD_AUTO_CORR32_X4_TH_ADD_MIN_INDEX (5)
#define HD_AUTO_CORR32_X4_TH_ADD_MIN_MRC_INDEX (6)
#define HD_BARKER_CORR_TH_ADD_MIN_INDEX (7)
#define HD_BARKER_CORR_TH_ADD_MIN_MRC_INDEX (8)
#define HD_AUTO_CORR40_X4_TH_ADD_MIN_INDEX (9)
#define HD_OFDM_ENERGY_TH_IN_INDEX (10)
/* Control field in struct iwl4965_sensitivity_cmd */
#define SENSITIVITY_CMD_CONTROL_DEFAULT_TABLE __constant_cpu_to_le16(0)
#define SENSITIVITY_CMD_CONTROL_WORK_TABLE __constant_cpu_to_le16(1)
/**
* struct iwl4965_sensitivity_cmd
* @control: (1) updates working table, (0) updates default table
* @table: energy threshold values, use HD_* as index into table
*
* Always use "1" in "control" to update uCode's working table and DSP.
*/
struct iwl4965_sensitivity_cmd {
__le16 control;
__le16 table[HD_TABLE_SIZE];
__le16 control; /* always use "1" */
__le16 table[HD_TABLE_SIZE]; /* use HD_* as index */
} __attribute__ ((packed));
/**
* REPLY_PHY_CALIBRATION_CMD = 0xb0 (command, has simple generic response)
*
* This command sets the relative gains of 4965's 3 radio receiver chains.
*
* After the first association, driver should accumulate signal and noise
* statistics from the STATISTICS_NOTIFICATIONs that follow the first 20
* beacons from the associated network (don't collect statistics that come
* in from scanning, or any other non-network source).
*
* DISCONNECTED ANTENNA:
*
* Driver should determine which antennas are actually connected, by comparing
* average beacon signal levels for the 3 Rx chains. Accumulate (add) the
* following values over 20 beacons, one accumulator for each of the chains
* a/b/c, from struct statistics_rx_non_phy:
*
* beacon_rssi_[abc] & 0x0FF (unsigned, units in dB)
*
* Find the strongest signal from among a/b/c. Compare the other two to the
* strongest. If any signal is more than 15 dB (times 20, unless you
* divide the accumulated values by 20) below the strongest, the driver
* considers that antenna to be disconnected, and should not try to use that
* antenna/chain for Rx or Tx. If both A and B seem to be disconnected,
* driver should declare the stronger one as connected, and attempt to use it
* (A and B are the only 2 Tx chains!).
*
*
* RX BALANCE:
*
* Driver should balance the 3 receivers (but just the ones that are connected
* to antennas, see above) for gain, by comparing the average signal levels
* detected during the silence after each beacon (background noise).
* Accumulate (add) the following values over 20 beacons, one accumulator for
* each of the chains a/b/c, from struct statistics_rx_non_phy:
*
* beacon_silence_rssi_[abc] & 0x0FF (unsigned, units in dB)
*
* Find the weakest background noise level from among a/b/c. This Rx chain
* will be the reference, with 0 gain adjustment. Attenuate other channels by
* finding noise difference:
*
* (accum_noise[i] - accum_noise[reference]) / 30
*
* The "30" adjusts the dB in the 20 accumulated samples to units of 1.5 dB.
* For use in diff_gain_[abc] fields of struct iwl_calibration_cmd, the
* driver should limit the difference results to a range of 0-3 (0-4.5 dB),
* and set bit 2 to indicate "reduce gain". The value for the reference
* (weakest) chain should be "0".
*
* diff_gain_[abc] bit fields:
* 2: (1) reduce gain, (0) increase gain
* 1-0: amount of gain, units of 1.5 dB
*/
/* "Differential Gain" opcode used in REPLY_PHY_CALIBRATION_CMD. */
#define PHY_CALIBRATE_DIFF_GAIN_CMD (7)
struct iwl4965_calibration_cmd {
u8 opCode;
u8 flags;
u8 opCode; /* PHY_CALIBRATE_DIFF_GAIN_CMD (7) */
u8 flags; /* not used */
__le16 reserved;
s8 diff_gain_a;
s8 diff_gain_a; /* see above */
s8 diff_gain_b;
s8 diff_gain_c;
u8 reserved1;

1
drivers/net/wireless/iwlwifi/iwl-4965.c
View File

@ -1068,6 +1068,7 @@ static int iwl4965_sensitivity_write(struct iwl4965_priv *priv, u8 flags)
data->auto_corr_cck, data->auto_corr_cck_mrc,
data->nrg_th_cck);
/* Update uCode's "work" table, and copy it to DSP */
cmd.control = SENSITIVITY_CMD_CONTROL_WORK_TABLE;
if (flags & CMD_ASYNC)

18
drivers/net/wireless/iwlwifi/iwl-4965.h
View File

@ -924,22 +924,6 @@ struct iwl4965_lq_mngr {
#define CAL_NUM_OF_BEACONS 20
#define MAXIMUM_ALLOWED_PATHLOSS 15
/* Param table within SENSITIVITY_CMD */
#define HD_MIN_ENERGY_CCK_DET_INDEX (0)
#define HD_MIN_ENERGY_OFDM_DET_INDEX (1)
#define HD_AUTO_CORR32_X1_TH_ADD_MIN_INDEX (2)
#define HD_AUTO_CORR32_X1_TH_ADD_MIN_MRC_INDEX (3)
#define HD_AUTO_CORR40_X4_TH_ADD_MIN_MRC_INDEX (4)
#define HD_AUTO_CORR32_X4_TH_ADD_MIN_INDEX (5)
#define HD_AUTO_CORR32_X4_TH_ADD_MIN_MRC_INDEX (6)
#define HD_BARKER_CORR_TH_ADD_MIN_INDEX (7)
#define HD_BARKER_CORR_TH_ADD_MIN_MRC_INDEX (8)
#define HD_AUTO_CORR40_X4_TH_ADD_MIN_INDEX (9)
#define HD_OFDM_ENERGY_TH_IN_INDEX (10)
#define SENSITIVITY_CMD_CONTROL_DEFAULT_TABLE __constant_cpu_to_le16(0)
#define SENSITIVITY_CMD_CONTROL_WORK_TABLE __constant_cpu_to_le16(1)
#define CHAIN_NOISE_MAX_DELTA_GAIN_CODE 3
#define MAX_FA_OFDM 50
@ -967,8 +951,6 @@ struct iwl4965_lq_mngr {
#define AUTO_CORR_STEP_CCK 3
#define AUTO_CORR_MAX_TH_CCK 160
#define NRG_ALG 0
#define AUTO_CORR_ALG 1
#define NRG_DIFF 2
#define NRG_STEP_CCK 2
#define NRG_MARGIN 8