1. 17 Jan, 2018 2 commits
  2. 15 Jan, 2018 20 commits
  3. 04 Jan, 2018 1 commit
    • Jan Kundrát's avatar
      i2c: gpio: Enable working over slow can_sleep GPIOs · f11a0446
      Jan Kundrát authored
      "Slow" GPIOs (usually those connected over an SPI or an I2C bus) are,
      well, slow in their operation. It is generally a good idea to avoid
      using them for time-critical operation, but sometimes the hardware just
      sucks, and the software has to cope. In addition to that, the I2C bus
      itself does not actually define any strict timing limits; the bus is
      free to go all the way down to DC. The timeouts (and therefore the
      slowest acceptable frequency) are present only in SMBus.
      
      The `can_sleep` is IMHO a wrong concept to use here. My SPI-to-quad-UART
      chip (MAX14830) is connected via a 26MHz SPI bus, and it happily drives
      SCL at 200kHz (5µs pulses) during my benchmarks. That's faster than the
      maximal allowed speed of the traditional I2C.
      
      The previous version of this code did not really block operation over
      slow GPIO pins, anyway. Instead, it just resorted to printing a warning
      with a backtrace each time a GPIO pin was accessed, thereby slowing
      things down even more.
      
      Finally, it's not just me. A similar patch was originally submitted in
      2015 [1].
      
      [1] https://patchwork.ozlabs.org/patch/450956/
      
      
      
      Signed-off-by: default avatarJan Kundrát <jan.kundrat@cesnet.cz>
      Acked-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
      Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
      f11a0446
  4. 03 Jan, 2018 4 commits
  5. 02 Jan, 2018 4 commits
  6. 01 Jan, 2018 9 commits