linux-kernel - [PATCH 0/6] 8250 DW UART fixes when under constant Rx pressure

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Message-Id: <20260123172739.13410-1-ilpo.jarvinen@linux.intel.com>
Date: Fri, 23 Jan 2026 19:27:33 +0200
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	linux-serial@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	qianfan Zhao <qianfanguijin@....com>,
	Adriana Nicolae <adriana@...sta.com>
Cc: linux-kernel@...r.kernel.org,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH 0/6] 8250 DW UART fixes when under constant Rx pressure

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).

I'll do UART_IIR_RX_TIMEOUT move to switch/case separately from this
fix series.

Ilpo Järvinen (6):
  serial: 8250: Protect LCR write in shutdown
  serial: 8250_dw: Avoid unnecessary LCR writes
  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   | 297 ++++++++++++++++++++++------
 drivers/tty/serial/8250/8250_port.c |  69 ++++---
 include/linux/serial_8250.h         |   1 +
 4 files changed, 301 insertions(+), 91 deletions(-)


base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
-- 
2.39.5