Hi all,

Here are fixes to 8250 DW UART conditions that mostly occur in scenarios
under constant Rx pressure which are made complicated by BUSY handling
of DW UARTs (used when !uart_16550_compatible).

A few of the changes touch also 8250_port but it's mostly moving existing
code around (except for the extra synchronize_irq() in shutdown).

Pending cleanups (to be sent separately):
 - 8250_dw: UART_IIR_RX_TIMEOUT move to switch/case 
 - 8250: include sorting
 - 8250: iir types to u8

v4:
- Fix warning about label at the end (due to commented out code) being
  an extension by adding an otherwise unnecessary return.

v3:
- Rollback dw8250_idle_enter() failures within
- usr_reg = ... ? ... : ...;
- Leave LCR write fail dev_err() where it was (commented out)

v2:
- Added Fixes tags pointing DW & INTC10EE introducing commits
- Added Cc stable to prerequisite patches
- Separate adding serial8250_handle_irq_locked() to own patch
- Put new exports to SERIAL_8250 namespace (eventually all 8250
  exports should move there, but out-of-scope for this series)
- Changes to no_int_count
	- Change type to u8
	- Use modulo in increment, add a define for it
	- Perform kick only on 4th NO_INT
- Use serial_port_in/out() throughout the series
- Add FIXME comments to ndelay(frame_time) about very low baud rates
- Add cleanup.h
- Tweak lockdep.h place among misordered includes
- Wording tweaks to changelogs and comments

Ilpo Järvinen (7):
  serial: 8250: Protect LCR write in shutdown
  serial: 8250_dw: Avoid unnecessary LCR writes
  serial: 8250: Add serial8250_handle_irq_locked()
  serial: 8250_dw: Rework dw8250_handle_irq() locking and IIR handling
  serial: 8250_dw: Rework IIR_NO_INT handling to stop interrupt storm
  serial: 8250: Add late synchronize_irq() to shutdown to handle DW UART
    BUSY
  serial: 8250_dw: Ensure BUSY is deasserted

 drivers/tty/serial/8250/8250.h      |  25 +++
 drivers/tty/serial/8250/8250_dw.c   | 296 ++++++++++++++++++++++------
 drivers/tty/serial/8250/8250_port.c |  69 ++++---
 include/linux/serial_8250.h         |   1 +
 4 files changed, 304 insertions(+), 87 deletions(-)


base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
-- 
2.39.5