1. 21 Jan, 2014 35 commits
  2. 08 Jan, 2014 3 commits
  3. 07 Jan, 2014 2 commits
    • Sebastian Andrzej Siewior's avatar
      mfd: input: iio: ti_amm335x: Rework TSC/ADC synchronization · 7ca6740c
      Sebastian Andrzej Siewior authored
      The ADC driver always programs all possible ADC values and discards
      them except for the value IIO asked for. On the am335x-evm the driver
      programs four values and it takes 500us to gather them. Reducing the number
      of conversations down to the (required) one also reduces the busy loop down
      to 125us.
      This leads to another error, namely the FIFOCOUNT register is sometimes
      (like one out of 10 attempts) not updated in time leading to EBUSY.
      The next read has the FIFOCOUNT register updated.
      Checking for the ADCSTAT register for being idle isn't a good choice either.
      The problem is that if TSC is used at the same time, the HW completes the
      conversation for ADC *and* before the driver noticed it, the HW begins to
      perform a TSC conversation and so the driver never seen the HW idle. The
      next time we would have two values in the FIFO but since the driver reads
      everything we always see the current one.
      So instead of polling for the IDLE bit in ADCStatus register, we should
      check the FIFOCOUNT register. It should be one instead of zero because we
      request one value.
      This change in turn leads to another error. Sometimes if TSC & ADC are
      used together the TSC starts generating interrupts even if nobody
      actually touched the touchscreen. The interrupts seem valid because TSC's
      FIFO is filled with values for each channel of the TSC. This condition stops
      after a few ADC reads but will occur again. Not good.
      On top of this (even without the changes I just mentioned) there is a ADC
      & TSC lockup condition which was reported to me by Jeff Lance including the
      following test case:
      A busy loop of "cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw"
      and a mug on touch screen. With this setup, the hardware will lockup after
      something between 20 minutes and it could take up to a couple of hours.
      During that lockup, the ADCSTAT register says 0x30 (or 0x70) which means
      STEP_ID = IDLE and FSM_BUSY = yes. That means the hardware says that it is
      idle and busy at the same time which is an invalid condition.
      For all this reasons I decided to rework this TSC/ADC part and add a
      handshake / synchronization here:
      First the ADC signals that it needs the HW and writes a 0 mask into the
      SE register. The HW (if active) will complete the current conversation
      and become idle. The TSC driver will gather the values from the FIFO
      (woken up by an interrupt) and won't "enable" another conversation.
      Instead it will wake up the ADC driver which is already waiting. The ADC
      driver will start "its" conversation and once it is done, it will
      enable the TSC steps so the TSC will work again.
      After this rework I haven't observed the lockup so far. Plus the busy
      loop has been reduced from 500us to 125us.
      The continues-read mode remains unchanged.
      Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
      Acked-by: default avatarJonathan Cameron <jic23@kernel.org>
      Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
    • Sebastian Andrzej Siewior's avatar
      mfd: ti_am335x: Drop am335x_tsc_se_update() from resume path · 3954b7bf
      Sebastian Andrzej Siewior authored
      The update of the SE register in MFD doesn't look right as it has
      nothing to do with it. The better place to do it is in TSC driver (which
      is already doing it) and in the ADC driver which needs this only in the
      continues mode.
      Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
      Acked-by: default avatarJonathan Cameron <jic23@kernel.org>
      Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>