In my project, I need to add 5/10MHZ channel width support function, my chip is ar9280.
       1. I don't know whether this chip support this function, because there is no information about this function in the
   datasheet which given by Atheros, but UBiquiti M2 support it, its chip is ar9283.
       2. I check the Madwifi source code and find that this function is not completed. The driver provide this function with a ioctl interface(iwpriv ath0 chanbw 0/1/2  0: full 1: half 2: quarter) to set ic->ic_chanbwflag , however, this value have not been used in anywhere.
      3. In the Hal layer, there is a function named ar5416InitPLL, It seems that this function provide channel width control. But it did not work when I set a fixed value for variable pll. I judged it by IQView equipment and a device worked in 20MHZ channel width can connect it.
      I really want to know whether ar9280 support 5/10MHZ channel width, if it works, which registers control it and how to set those register. I guess the registers are AR_PHY_PLL_CTL(#define AR_PHY_PLL_CTL  0x987c  /* PLL control register */) or AR_RTC_PLL_CONTROL(#define AR_RTC_PLL_CONTROL      0x7014).
      Any help will be appreciated.
Best Regards