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iwlwifi: document temperature calculation 

Document temperature calculation

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 11:10:01 +08:00 committed by David S. Miller
parent fcd427bbba
commit 5991b419f0
1 changed files with 46 additions and 11 deletions
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57
drivers/net/wireless/iwlwifi/iwl-4965-hw.h
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@ -645,6 +645,52 @@ static inline int iwl4965_hw_valid_rtc_data_addr(u32 addr)
(addr < KDR_RTC_DATA_UPPER_BOUND);
}
/********************* START TEMPERATURE *************************************/
/*
* 4965 temperature calculation.
*
* The driver must calculate the device temperature before calculating
* a txpower setting (amplifier gain is temperature dependent). The
* calculation uses 4 measurements, 3 of which (R1, R2, R3) are calibration
* values used for the life of the driver, and one of which (R4) is the
* real-time temperature indicator.
*
* uCode provides all 4 values to the driver via the "initialize alive"
* notification (see struct iwl4965_init_alive_resp). After the runtime uCode
* image loads, uCode updates the R4 value via statistics notifications
* (see STATISTICS_NOTIFICATION), which occur after each received beacon
* when associated, or can be requested via REPLY_STATISTICS_CMD.
*
* NOTE: uCode provides the R4 value as a 23-bit signed value. Driver
* must sign-extend to 32 bits before applying formula below.
*
* Formula:
*
* degrees Kelvin = ((97 * 259 * (R4 - R2) / (R3 - R1)) / 100) + 8
*
* NOTE: The basic formula is 259 * (R4-R2) / (R3-R1). The 97/100 is
* an additional correction, which should be centered around 0 degrees
* Celsius (273 degrees Kelvin). The 8 (3 percent of 273) compensates for
* centering the 97/100 correction around 0 degrees K.
*
* Add 273 to Kelvin value to find degrees Celsius, for comparing current
* temperature with factory-measured temperatures when calculating txpower
* settings.
*/
#define TEMPERATURE_CALIB_KELVIN_OFFSET 8
#define TEMPERATURE_CALIB_A_VAL 259
/* Limit range of calculated temperature to be between these Kelvin values */
#define IWL_TX_POWER_TEMPERATURE_MIN (263)
#define IWL_TX_POWER_TEMPERATURE_MAX (410)
#define IWL_TX_POWER_TEMPERATURE_OUT_OF_RANGE(t) \
(((t) < IWL_TX_POWER_TEMPERATURE_MIN) || \
((t) > IWL_TX_POWER_TEMPERATURE_MAX))
/********************* END TEMPERATURE ***************************************/
/********************* START TXPOWER *****************************************/
enum {
@ -656,17 +702,6 @@ enum {
CALIB_CH_GROUP_MAX
};
/* Temperature calibration offset is 3% 0C in Kelvin */
#define TEMPERATURE_CALIB_KELVIN_OFFSET 8
#define TEMPERATURE_CALIB_A_VAL 259
#define IWL_TX_POWER_TEMPERATURE_MIN (263)
#define IWL_TX_POWER_TEMPERATURE_MAX (410)
#define IWL_TX_POWER_TEMPERATURE_OUT_OF_RANGE(t) \
(((t) < IWL_TX_POWER_TEMPERATURE_MIN) || \
((t) > IWL_TX_POWER_TEMPERATURE_MAX))
#define IWL_TX_POWER_MIMO_REGULATORY_COMPENSATION (6)
#define IWL_TX_POWER_TARGET_POWER_MIN (0) /* 0 dBm = 1 milliwatt */