From: Ben Cahill Date: Thu, 29 Nov 2007 03:10:02 +0000 (+0800) Subject: iwlwifi: document txpower calculations X-Git-Tag: v2.6.25-rc1~1162^2~488 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0c434c5a7f9983c8ee3c8943924db8c5fb1d12bd;p=linux-2.6 iwlwifi: document txpower calculations Document txpower calculations 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-hw.h b/drivers/net/wireless/iwlwifi/iwl-4965-hw.h index 78d9854f75..4a2fa80acf 100644 --- a/drivers/net/wireless/iwlwifi/iwl-4965-hw.h +++ b/drivers/net/wireless/iwlwifi/iwl-4965-hw.h @@ -647,7 +647,7 @@ static inline int iwl4965_hw_valid_rtc_data_addr(u32 addr) /********************* START TEMPERATURE *************************************/ -/* +/** * 4965 temperature calculation. * * The driver must calculate the device temperature before calculating @@ -693,44 +693,593 @@ static inline int iwl4965_hw_valid_rtc_data_addr(u32 addr) /********************* START TXPOWER *****************************************/ -enum { - CALIB_CH_GROUP_1 = 0, - CALIB_CH_GROUP_2 = 1, - CALIB_CH_GROUP_3 = 2, - CALIB_CH_GROUP_4 = 3, - CALIB_CH_GROUP_5 = 4, - CALIB_CH_GROUP_MAX -}; +/** + * 4965 txpower calculations rely on information from three sources: + * + * 1) EEPROM + * 2) "initialize" alive notification + * 3) statistics notifications + * + * EEPROM data consists of: + * + * 1) Regulatory information (max txpower and channel usage flags) is provided + * separately for each channel that can possibly supported by 4965. + * 40 MHz wide (.11n fat) channels are listed separately from 20 MHz + * (legacy) channels. + * + * See struct iwl4965_eeprom_channel for format, and struct iwl4965_eeprom + * for locations in EEPROM. + * + * 2) Factory txpower calibration information is provided separately for + * sub-bands of contiguous channels. 2.4GHz has just one sub-band, + * but 5 GHz has several sub-bands. + * + * In addition, per-band (2.4 and 5 Ghz) saturation txpowers are provided. + * + * See struct iwl4965_eeprom_calib_info (and the tree of structures + * contained within it) for format, and struct iwl4965_eeprom for + * locations in EEPROM. + * + * "Initialization alive" notification (see struct iwl4965_init_alive_resp) + * consists of: + * + * 1) Temperature calculation parameters. + * + * 2) Power supply voltage measurement. + * + * 3) Tx gain compensation to balance 2 transmitters for MIMO use. + * + * Statistics notifications deliver: + * + * 1) Current values for temperature param R4. + */ -#define IWL_TX_POWER_MIMO_REGULATORY_COMPENSATION (6) +/** + * To calculate a txpower setting for a given desired target txpower, channel, + * modulation bit rate, and transmitter chain (4965 has 2 transmitters to + * support MIMO and transmit diversity), driver must do the following: + * + * 1) Compare desired txpower vs. (EEPROM) regulatory limit for this channel. + * Do not exceed regulatory limit; reduce target txpower if necessary. + * + * If setting up txpowers for MIMO rates (rate indexes 8-15, 24-31), + * 2 transmitters will be used simultaneously; driver must reduce the + * regulatory limit by 3 dB (half-power) for each transmitter, so the + * combined total output of the 2 transmitters is within regulatory limits. + * + * + * 2) Compare target txpower vs. (EEPROM) saturation txpower *reduced by + * backoff for this bit rate*. Do not exceed (saturation - backoff[rate]); + * reduce target txpower if necessary. + * + * Backoff values below are in 1/2 dB units (equivalent to steps in + * txpower gain tables): + * + * OFDM 6 - 36 MBit: 10 steps (5 dB) + * OFDM 48 MBit: 15 steps (7.5 dB) + * OFDM 54 MBit: 17 steps (8.5 dB) + * OFDM 60 MBit: 20 steps (10 dB) + * CCK all rates: 10 steps (5 dB) + * + * Backoff values apply to saturation txpower on a per-transmitter basis; + * when using MIMO (2 transmitters), each transmitter uses the same + * saturation level provided in EEPROM, and the same backoff values; + * no reduction (such as with regulatory txpower limits) is required. + * + * Saturation and Backoff values apply equally to 20 Mhz (legacy) channel + * widths and 40 Mhz (.11n fat) channel widths; there is no separate + * factory measurement for fat channels. + * + * The result of this step is the final target txpower. The rest of + * the steps figure out the proper settings for the device to achieve + * that target txpower. + * + * + * 3) Determine (EEPROM) calibration subband for the target channel, by + * comparing against first and last channels in each subband + * (see struct iwl4965_eeprom_calib_subband_info). + * + * + * 4) Linearly interpolate (EEPROM) factory calibration measurement sets, + * referencing the 2 factory-measured (sample) channels within the subband. + * + * Interpolation is based on difference between target channel's frequency + * and the sample channels' frequencies. Since channel numbers are based + * on frequency (5 MHz between each channel number), this is equivalent + * to interpolating based on channel number differences. + * + * Note that the sample channels may or may not be the channels at the + * edges of the subband. The target channel may be "outside" of the + * span of the sampled channels. + * + * Driver may choose the pair (for 2 Tx chains) of measurements (see + * struct iwl4965_eeprom_calib_ch_info) for which the actual measured + * txpower comes closest to the desired txpower. Usually, though, + * the middle set of measurements is closest to the regulatory limits, + * and is therefore a good choice for all txpower calculations (this + * assumes that high accuracy is needed for maximizing legal txpower, + * while lower txpower configurations do not need as much accuracy). + * + * Driver should interpolate both members of the chosen measurement pair, + * i.e. for both Tx chains (radio transmitters), unless the driver knows + * that only one of the chains will be used (e.g. only one tx antenna + * connected, but this should be unusual). The rate scaling algorithm + * switches antennas to find best performance, so both Tx chains will + * be used (although only one at a time) even for non-MIMO transmissions. + * + * Driver should interpolate factory values for temperature, gain table + * index, and actual power. The power amplifier detector values are + * not used by the driver. + * + * Sanity check: If the target channel happens to be one of the sample + * channels, the results should agree with the sample channel's + * measurements! + * + * + * 5) Find difference between desired txpower and (interpolated) + * factory-measured txpower. Using (interpolated) factory gain table index + * (shown elsewhere) as a starting point, adjust this index lower to + * increase txpower, or higher to decrease txpower, until the target + * txpower is reached. Each step in the gain table is 1/2 dB. + * + * For example, if factory measured txpower is 16 dBm, and target txpower + * is 13 dBm, add 6 steps to the factory gain index to reduce txpower + * by 3 dB. + * + * + * 6) Find difference between current device temperature and (interpolated) + * factory-measured temperature for sub-band. Factory values are in + * degrees Celsius. To calculate current temperature, see comments for + * "4965 temperature calculation". + * + * If current temperature is higher than factory temperature, driver must + * increase gain (lower gain table index), and vice versa. + * + * Temperature affects gain differently for different channels: + * + * 2.4 GHz all channels: 3.5 degrees per half-dB step + * 5 GHz channels 34-43: 4.5 degrees per half-dB step + * 5 GHz channels >= 44: 4.0 degrees per half-dB step + * + * NOTE: Temperature can increase rapidly when transmitting, especially + * with heavy traffic at high txpowers. Driver should update + * temperature calculations often under these conditions to + * maintain strong txpower in the face of rising temperature. + * + * + * 7) Find difference between current power supply voltage indicator + * (from "initialize alive") and factory-measured power supply voltage + * indicator (EEPROM). + * + * If the current voltage is higher (indicator is lower) than factory + * voltage, gain should be reduced (gain table index increased) by: + * + * (eeprom - current) / 7 + * + * If the current voltage is lower (indicator is higher) than factory + * voltage, gain should be increased (gain table index decreased) by: + * + * 2 * (current - eeprom) / 7 + * + * If number of index steps in either direction turns out to be > 2, + * something is wrong ... just use 0. + * + * NOTE: Voltage compensation is independent of band/channel. + * + * NOTE: "Initialize" uCode measures current voltage, which is assumed + * to be constant after this initial measurement. Voltage + * compensation for txpower (number of steps in gain table) + * may be calculated once and used until the next uCode bootload. + * + * + * 8) If setting up txpowers for MIMO rates (rate indexes 8-15, 24-31), + * adjust txpower for each transmitter chain, so txpower is balanced + * between the two chains. There are 5 pairs of tx_atten[group][chain] + * values in "initialize alive", one pair for each of 5 channel ranges: + * + * Group 0: 5 GHz channel 34-43 + * Group 1: 5 GHz channel 44-70 + * Group 2: 5 GHz channel 71-124 + * Group 3: 5 GHz channel 125-200 + * Group 4: 2.4 GHz all channels + * + * Add the tx_atten[group][chain] value to the index for the target chain. + * The values are signed, but are in pairs of 0 and a non-negative number, + * so as to reduce gain (if necessary) of the "hotter" channel. This + * avoids any need to double-check for regulatory compliance after + * this step. + * + * + * 9) If setting up for a CCK rate, lower the gain by adding a CCK compensation + * value to the index: + * + * Hardware rev B: 9 steps (4.5 dB) + * Hardware rev C: 5 steps (2.5 dB) + * + * Hardware rev for 4965 can be determined by reading CSR_HW_REV_WA_REG, + * bits [3:2], 1 = B, 2 = C. + * + * NOTE: This compensation is in addition to any saturation backoff that + * might have been applied in an earlier step. + * + * + * 10) Select the gain table, based on band (2.4 vs 5 GHz). + * + * Limit the adjusted index to stay within the table! + * + * + * 11) Read gain table entries for DSP and radio gain, place into appropriate + * location(s) in command (struct iwl4965_txpowertable_cmd). + */ +/* Limit range of txpower output target to be between these values */ #define IWL_TX_POWER_TARGET_POWER_MIN (0) /* 0 dBm = 1 milliwatt */ #define IWL_TX_POWER_TARGET_POWER_MAX (16) /* 16 dBm */ -#define MIN_TX_GAIN_INDEX (0) -#define MIN_TX_GAIN_INDEX_52GHZ_EXT (-9) +/** + * When MIMO is used (2 transmitters operating simultaneously), driver should + * limit each transmitter to deliver a max of 3 dB below the regulatory limit + * for the device. That is, use half power for each transmitter, so total + * txpower is within regulatory limits. + * + * The value "6" represents number of steps in gain table to reduce power 3 dB. + * Each step is 1/2 dB. + */ +#define IWL_TX_POWER_MIMO_REGULATORY_COMPENSATION (6) + +/** + * CCK gain compensation. + * + * When calculating txpowers for CCK, after making sure that the target power + * is within regulatory and saturation limits, driver must additionally + * back off gain by adding these values to the gain table index. + * + * Hardware rev for 4965 can be determined by reading CSR_HW_REV_WA_REG, + * bits [3:2], 1 = B, 2 = C. + */ +#define IWL_TX_POWER_CCK_COMPENSATION_B_STEP (9) +#define IWL_TX_POWER_CCK_COMPENSATION_C_STEP (5) + +/* + * 4965 power supply voltage compensation for txpower + */ +#define TX_POWER_IWL_VOLTAGE_CODES_PER_03V (7) + +/** + * Gain tables. + * + * The following tables contain pair of values for setting txpower, i.e. + * gain settings for the output of the device's digital signal processor (DSP), + * and for the analog gain structure of the transmitter. + * + * Each entry in the gain tables represents a step of 1/2 dB. Note that these + * are *relative* steps, not indications of absolute output power. Output + * power varies with temperature, voltage, and channel frequency, and also + * requires consideration of average power (to satisfy regulatory constraints), + * and peak power (to avoid distortion of the output signal). + * + * Each entry contains two values: + * 1) DSP gain (or sometimes called DSP attenuation). This is a fine-grained + * linear value that multiplies the output of the digital signal processor, + * before being sent to the analog radio. + * 2) Radio gain. This sets the analog gain of the radio Tx path. + * It is a coarser setting, and behaves in a logarithmic (dB) fashion. + * + * EEPROM contains factory calibration data for txpower. This maps actual + * measured txpower levels to gain settings in the "well known" tables + * below ("well-known" means here that both factory calibration *and* the + * driver work with the same table). + * + * There are separate tables for 2.4 GHz and 5 GHz bands. The 5 GHz table + * has an extension (into negative indexes), in case the driver needs to + * boost power setting for high device temperatures (higher than would be + * present during factory calibration). A 5 Ghz EEPROM index of "40" + * corresponds to the 49th entry in the table used by the driver. + */ +#define MIN_TX_GAIN_INDEX (0) /* highest gain, lowest idx, 2.4 */ +#define MIN_TX_GAIN_INDEX_52GHZ_EXT (-9) /* highest gain, lowest idx, 5 */ + +/** + * 2.4 GHz gain table + * + * Index Dsp gain Radio gain + * 0 110 0x3f (highest gain) + * 1 104 0x3f + * 2 98 0x3f + * 3 110 0x3e + * 4 104 0x3e + * 5 98 0x3e + * 6 110 0x3d + * 7 104 0x3d + * 8 98 0x3d + * 9 110 0x3c + * 10 104 0x3c + * 11 98 0x3c + * 12 110 0x3b + * 13 104 0x3b + * 14 98 0x3b + * 15 110 0x3a + * 16 104 0x3a + * 17 98 0x3a + * 18 110 0x39 + * 19 104 0x39 + * 20 98 0x39 + * 21 110 0x38 + * 22 104 0x38 + * 23 98 0x38 + * 24 110 0x37 + * 25 104 0x37 + * 26 98 0x37 + * 27 110 0x36 + * 28 104 0x36 + * 29 98 0x36 + * 30 110 0x35 + * 31 104 0x35 + * 32 98 0x35 + * 33 110 0x34 + * 34 104 0x34 + * 35 98 0x34 + * 36 110 0x33 + * 37 104 0x33 + * 38 98 0x33 + * 39 110 0x32 + * 40 104 0x32 + * 41 98 0x32 + * 42 110 0x31 + * 43 104 0x31 + * 44 98 0x31 + * 45 110 0x30 + * 46 104 0x30 + * 47 98 0x30 + * 48 110 0x6 + * 49 104 0x6 + * 50 98 0x6 + * 51 110 0x5 + * 52 104 0x5 + * 53 98 0x5 + * 54 110 0x4 + * 55 104 0x4 + * 56 98 0x4 + * 57 110 0x3 + * 58 104 0x3 + * 59 98 0x3 + * 60 110 0x2 + * 61 104 0x2 + * 62 98 0x2 + * 63 110 0x1 + * 64 104 0x1 + * 65 98 0x1 + * 66 110 0x0 + * 67 104 0x0 + * 68 98 0x0 + * 69 97 0 + * 70 96 0 + * 71 95 0 + * 72 94 0 + * 73 93 0 + * 74 92 0 + * 75 91 0 + * 76 90 0 + * 77 89 0 + * 78 88 0 + * 79 87 0 + * 80 86 0 + * 81 85 0 + * 82 84 0 + * 83 83 0 + * 84 82 0 + * 85 81 0 + * 86 80 0 + * 87 79 0 + * 88 78 0 + * 89 77 0 + * 90 76 0 + * 91 75 0 + * 92 74 0 + * 93 73 0 + * 94 72 0 + * 95 71 0 + * 96 70 0 + * 97 69 0 + * 98 68 0 + */ + +/** + * 5 GHz gain table + * + * Index Dsp gain Radio gain + * -9 123 0x3F (highest gain) + * -8 117 0x3F + * -7 110 0x3F + * -6 104 0x3F + * -5 98 0x3F + * -4 110 0x3E + * -3 104 0x3E + * -2 98 0x3E + * -1 110 0x3D + * 0 104 0x3D + * 1 98 0x3D + * 2 110 0x3C + * 3 104 0x3C + * 4 98 0x3C + * 5 110 0x3B + * 6 104 0x3B + * 7 98 0x3B + * 8 110 0x3A + * 9 104 0x3A + * 10 98 0x3A + * 11 110 0x39 + * 12 104 0x39 + * 13 98 0x39 + * 14 110 0x38 + * 15 104 0x38 + * 16 98 0x38 + * 17 110 0x37 + * 18 104 0x37 + * 19 98 0x37 + * 20 110 0x36 + * 21 104 0x36 + * 22 98 0x36 + * 23 110 0x35 + * 24 104 0x35 + * 25 98 0x35 + * 26 110 0x34 + * 27 104 0x34 + * 28 98 0x34 + * 29 110 0x33 + * 30 104 0x33 + * 31 98 0x33 + * 32 110 0x32 + * 33 104 0x32 + * 34 98 0x32 + * 35 110 0x31 + * 36 104 0x31 + * 37 98 0x31 + * 38 110 0x30 + * 39 104 0x30 + * 40 98 0x30 + * 41 110 0x25 + * 42 104 0x25 + * 43 98 0x25 + * 44 110 0x24 + * 45 104 0x24 + * 46 98 0x24 + * 47 110 0x23 + * 48 104 0x23 + * 49 98 0x23 + * 50 110 0x22 + * 51 104 0x18 + * 52 98 0x18 + * 53 110 0x17 + * 54 104 0x17 + * 55 98 0x17 + * 56 110 0x16 + * 57 104 0x16 + * 58 98 0x16 + * 59 110 0x15 + * 60 104 0x15 + * 61 98 0x15 + * 62 110 0x14 + * 63 104 0x14 + * 64 98 0x14 + * 65 110 0x13 + * 66 104 0x13 + * 67 98 0x13 + * 68 110 0x12 + * 69 104 0x08 + * 70 98 0x08 + * 71 110 0x07 + * 72 104 0x07 + * 73 98 0x07 + * 74 110 0x06 + * 75 104 0x06 + * 76 98 0x06 + * 77 110 0x05 + * 78 104 0x05 + * 79 98 0x05 + * 80 110 0x04 + * 81 104 0x04 + * 82 98 0x04 + * 83 110 0x03 + * 84 104 0x03 + * 85 98 0x03 + * 86 110 0x02 + * 87 104 0x02 + * 88 98 0x02 + * 89 110 0x01 + * 90 104 0x01 + * 91 98 0x01 + * 92 110 0x00 + * 93 104 0x00 + * 94 98 0x00 + * 95 93 0x00 + * 96 88 0x00 + * 97 83 0x00 + * 98 78 0x00 + */ + +/** + * Sanity checks and default values for EEPROM regulatory levels. + * If EEPROM values fall outside MIN/MAX range, use default values. + * + * Regulatory limits refer to the maximum average txpower allowed by + * regulatory agencies in the geographies in which the device is meant + * to be operated. These limits are SKU-specific (i.e. geography-specific), + * and channel-specific; each channel has an individual regulatory limit + * listed in the EEPROM. + * + * Units are in half-dBm (i.e. "34" means 17 dBm). + */ #define IWL_TX_POWER_DEFAULT_REGULATORY_24 (34) #define IWL_TX_POWER_DEFAULT_REGULATORY_52 (34) #define IWL_TX_POWER_REGULATORY_MIN (0) #define IWL_TX_POWER_REGULATORY_MAX (34) + +/** + * Sanity checks and default values for EEPROM saturation levels. + * If EEPROM values fall outside MIN/MAX range, use default values. + * + * Saturation is the highest level that the output power amplifier can produce + * without significant clipping distortion. This is a "peak" power level. + * Different types of modulation (i.e. various "rates", and OFDM vs. CCK) + * require differing amounts of backoff, relative to their average power output, + * in order to avoid clipping distortion. + * + * Driver must make sure that it is violating neither the saturation limit, + * nor the regulatory limit, when calculating Tx power settings for various + * rates. + * + * Units are in half-dBm (i.e. "38" means 19 dBm). + */ #define IWL_TX_POWER_DEFAULT_SATURATION_24 (38) #define IWL_TX_POWER_DEFAULT_SATURATION_52 (38) #define IWL_TX_POWER_SATURATION_MIN (20) #define IWL_TX_POWER_SATURATION_MAX (50) -/* First and last channels of all groups */ +/** + * Channel groups used for Tx Attenuation calibration (MIMO tx channel balance) + * and thermal Txpower calibration. + * + * When calculating txpower, driver must compensate for current device + * temperature; higher temperature requires higher gain. Driver must calculate + * current temperature (see "4965 temperature calculation"), then compare vs. + * factory calibration temperature in EEPROM; if current temperature is higher + * than factory temperature, driver must *increase* gain by proportions shown + * in table below. If current temperature is lower than factory, driver must + * *decrease* gain. + * + * Different frequency ranges require different compensation, as shown below. + */ +/* Group 0, 5.2 GHz ch 34-43: 4.5 degrees per 1/2 dB. */ #define CALIB_IWL_TX_ATTEN_GR1_FCH 34 #define CALIB_IWL_TX_ATTEN_GR1_LCH 43 + +/* Group 1, 5.3 GHz ch 44-70: 4.0 degrees per 1/2 dB. */ #define CALIB_IWL_TX_ATTEN_GR2_FCH 44 #define CALIB_IWL_TX_ATTEN_GR2_LCH 70 + +/* Group 2, 5.5 GHz ch 71-124: 4.0 degrees per 1/2 dB. */ #define CALIB_IWL_TX_ATTEN_GR3_FCH 71 #define CALIB_IWL_TX_ATTEN_GR3_LCH 124 + +/* Group 3, 5.7 GHz ch 125-200: 4.0 degrees per 1/2 dB. */ #define CALIB_IWL_TX_ATTEN_GR4_FCH 125 #define CALIB_IWL_TX_ATTEN_GR4_LCH 200 + +/* Group 4, 2.4 GHz all channels: 3.5 degrees per 1/2 dB. */ #define CALIB_IWL_TX_ATTEN_GR5_FCH 1 #define CALIB_IWL_TX_ATTEN_GR5_LCH 20 +enum { + CALIB_CH_GROUP_1 = 0, + CALIB_CH_GROUP_2 = 1, + CALIB_CH_GROUP_3 = 2, + CALIB_CH_GROUP_4 = 3, + CALIB_CH_GROUP_5 = 4, + CALIB_CH_GROUP_MAX +}; + /********************* END TXPOWER *****************************************/ /* Flow Handler Definitions */ diff --git a/drivers/net/wireless/iwlwifi/iwl-4965.h b/drivers/net/wireless/iwlwifi/iwl-4965.h index 4a1ec9442c..2930c10b5e 100644 --- a/drivers/net/wireless/iwlwifi/iwl-4965.h +++ b/drivers/net/wireless/iwlwifi/iwl-4965.h @@ -859,9 +859,6 @@ struct iwl4965_kw { #define NUM_RX_CHAINS (3) #define TX_POWER_IWL_ILLEGAL_VOLTAGE -10000 -#define TX_POWER_IWL_VOLTAGE_CODES_PER_03V 7 -#define IWL_TX_POWER_CCK_COMPENSATION_B_STEP (9) -#define IWL_TX_POWER_CCK_COMPENSATION_C_STEP (5) struct iwl4965_traffic_load { unsigned long time_stamp;