[PATCH v3 0/7] serial: qcom-geni: Overhaul TX handling to fix crashes/hangs

[Douglas Anderson]

While trying to reproduce -EBUSY errors that our lab was getting in
suspend/resume testing, I ended up finding a whole pile of problems
with the Qualcomm GENI serial driver. I've posted a fix for the -EBUSY
issue separately [1]. This series is fixing all of the Qualcomm GENI
problems that I found.

As far as I can tell most of the problems have been in the Qualcomm
GENI serial driver since inception, but it can be noted that the
behavior got worse with the new kfifo changes. Previously when the OS
took data out of the circular queue we'd just spit stale data onto the
serial port. Now we'll hard lockup. :-P

I've tried to break this series up as much as possible to make it
easier to understand but the final patch is still a lot of change at
once. Hopefully it's OK.

[1] https://lore.kernel.org/r/20240530084841.v2.1.I2395e66cf70c6e67d774c56943825c289b9c13e4@changeid

Changes in v3:
- 0xffffffff => GENMASK(31, 0)
- Reword commit message.
- Use uart_fifo_timeout() for timeout.

Changes in v2:
- Totally rework / rename patch to handle suspend while active xfer
- serial: qcom-geni: Fix arg types for qcom_geni_serial_poll_bit()
- serial: qcom-geni: Fix the timeout in qcom_geni_serial_poll_bit()
- serial: qcom-geni: Introduce qcom_geni_serial_poll_bitfield()
- serial: qcom-geni: Just set the watermark level once
- serial: qcom-geni: Rework TX in FIFO mode to fix hangs/lockups
- soc: qcom: geni-se: Add GP_LENGTH/IRQ_EN_SET/IRQ_EN_CLEAR registers

Douglas Anderson (7):
  soc: qcom: geni-se: Add GP_LENGTH/IRQ_EN_SET/IRQ_EN_CLEAR registers
  serial: qcom-geni: Fix the timeout in qcom_geni_serial_poll_bit()
  serial: qcom-geni: Fix arg types for qcom_geni_serial_poll_bit()
  serial: qcom-geni: Introduce qcom_geni_serial_poll_bitfield()
  serial: qcom-geni: Just set the watermark level once
  serial: qcom-geni: Fix suspend while active UART xfer
  serial: qcom-geni: Rework TX in FIFO mode to fix hangs/lockups

 drivers/tty/serial/qcom_geni_serial.c | 321 +++++++++++++++-----------
 include/linux/soc/qcom/geni-se.h      |   6 +
 2 files changed, 192 insertions(+), 135 deletions(-)

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2.45.1.288.g0e0cd299f1-goog