1. 10 May, 2013 1 commit
    • Lokesh Vutla's avatar
      ARM: OMAP5: Fix warm reset with USB cable connected · 0b1b60c7
      Lokesh Vutla authored
      Warm reset on OMAP5 freezes when USB cable is connected.
      Fix requires PRM_RSTTIME.RSTTIME1 to be programmed
      with the time for which reset should be held low for the
      voltages and the oscillator to reach stable state.
      
      There are 3 parameters to be considered for calculating
      the time, which are mostly board and PMIC dependent.
      -1- Time taken by the Oscillator to shut + restart
      -2- PMIC OTP times
      -3- Voltage rail ramp times, which inturn depends on the
      PMIC slew rate and value of the voltage ramp needed.
      
      In order to keep the code in u-boot simple, have a way
      for boards to specify a pre computed time directly using
      the 'CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC'
      option. If boards fail to specify the time, use a default
      as specified by 'CONFIG_DEFAULT_OMAP_RESET_TIME_MAX_USEC' instead.
      Using the default value translates into some ~22ms and should work in
      all cases.
      However in order to avoid this large delay hiding other bugs,
      its recommended that all boards look at their respective data
      sheets and specify a pre computed and optimal value using
      'CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC'
      
      In order to help future board additions to compute this
      config option value, add a README at doc/README.omap-reset-time
      which explains how to compute the value. Also update the toplevel
      README with the additional option and pointers to
      doc/README.omap-reset-time.
      Signed-off-by: 's avatarLokesh Vutla <lokeshvutla@ti.com>
      [rnayak@ti.com: Updated changelog and added the README]
      Signed-off-by: 's avatarRajendra Nayak <rnayak@ti.com>
      0b1b60c7