From: Ben Cahill Date: Thu, 29 Nov 2007 03:09:51 +0000 (+0800) Subject: iwlwifi: Document Rx calibration X-Git-Tag: v2.6.25-rc1~1162^2~498 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f7d09d7c453f197d802c50172b27170a43e1a816;p=linux-2.6 iwlwifi: Document Rx calibration Document Rx calibration Signed-off-by: Ben Cahill Signed-off-by: Zhu Yi Signed-off-by: John W. Linville --- diff --git a/drivers/net/wireless/iwlwifi/iwl-4965-commands.h b/drivers/net/wireless/iwlwifi/iwl-4965-commands.h index 00d4ab7c7a..575a065f8e 100644 --- a/drivers/net/wireless/iwlwifi/iwl-4965-commands.h +++ b/drivers/net/wireless/iwlwifi/iwl-4965-commands.h @@ -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; diff --git a/drivers/net/wireless/iwlwifi/iwl-4965.c b/drivers/net/wireless/iwlwifi/iwl-4965.c index 7d95de9d03..d44166a599 100644 --- a/drivers/net/wireless/iwlwifi/iwl-4965.c +++ b/drivers/net/wireless/iwlwifi/iwl-4965.c @@ -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) diff --git a/drivers/net/wireless/iwlwifi/iwl-4965.h b/drivers/net/wireless/iwlwifi/iwl-4965.h index af3497442a..321767f539 100644 --- a/drivers/net/wireless/iwlwifi/iwl-4965.h +++ b/drivers/net/wireless/iwlwifi/iwl-4965.h @@ -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