Pkshih <pkshih@xxxxxxxxxxx> 於 2021年3月6日 週六 下午1:09寫道： > > On Tue, 2021-03-02 at 10:21 +0000, 邱名碩 wrote: > > Hi guys, > > I'm planning to implement the get_txpower hook function of the > > struct ieee80211_ops and handle the IEEE80211_CONF_CHANGE_POWER for > > rtl8xxxu driver. So that users can get the information of the current > > tx power limit and set a new limit value with iw commands. > > > > I found there's phy_txpwr_idx_to_dbm() of each driver in > > realtek/rtlwifi to translate the tx power index parsed from efuse to > > tx power level in dBm. Does the power level translated represent the > > current tx power limit in dBm? In my RTL8188CUS module, the power > > index of CCK/OFDM from efuse for each channel is basically 36/38, thus > > the translated txpower level is 11dBm. Is this the expected value for > > the default txpower limit value? Or do I need some other formula to > > compute? > > Basically, you can use a linear equation to translate power level in dBm to > tx power index written to hardware registers. > y = ax + b > where, > y: tx power index written to registers > x: tx power level in dBm > a: a constant, 2 > b: a constant induced by the value programmed in efuse that is used to > adapt modules differences of RF characters. > Thanks so much. So it means that the txpwr_idx_to_dbm and dbm_to_idx functions in rtlwifi family driver are basically correct. Except they use the constant b -7 for CCK and -8 for OFDM instead of the value in efuse. I should have this value from efuse. > > > > And for the handler of IEEE80211_CONF_CHANGE_POWER, can I > > translate the hw->conf.power_level with the phy_dbm_to_txpwr_idx > > functions I found in some rtlwifi family drivers, then directly set > > the txpower index with phy_set_txpower_index functions which write > > power index to bbreg for different rates (CCK and OFDM)? Are there > > some invalid values I should take care of because the TCP RX > > performance seems to be extremely low when I write the power index > > value translated from 20dBm to bbreg. Any suggestions for what I > > should handle before writing the bbreg? > > The power level you're going to set must be less or equal to original > one, because it's the hard limit of hardware capability. If the power > level is too large, the receiver can't understand the signal. Then, > they can't exchange data that leads low performance as you see. > I think the performance would be okay if you connect to a near AP and > power level 10dBm is adapted. > Thanks for clarification. So the power index from efuse is basically the hard limit of the tx power for each channel (and rate)? That explains my performance issue while I override it with higher value. Thanks Chris > > --- > Ping-Ke >
