queue-6.8/serial-mxs-auart-add-spinlock-around-changing-cts-state.patch

   1 From 54c4ec5f8c471b7c1137a1f769648549c423c026 Mon Sep 17 00:00:00 2001
   2 From: Emil Kronborg <emil.kronborg@protonmail.com>
   3 Date: Wed, 20 Mar 2024 12:15:36 +0000
   4 Subject: serial: mxs-auart: add spinlock around changing cts state
   5
   6 From: Emil Kronborg <emil.kronborg@protonmail.com>
   7
   8 commit 54c4ec5f8c471b7c1137a1f769648549c423c026 upstream.
   9
  10 The uart_handle_cts_change() function in serial_core expects the caller
  11 to hold uport->lock. For example, I have seen the below kernel splat,
  12 when the Bluetooth driver is loaded on an i.MX28 board.
  13
  14     [   85.119255] ------------[ cut here ]------------
  15     [   85.124413] WARNING: CPU: 0 PID: 27 at /drivers/tty/serial/serial_core.c:3453 uart_handle_cts_change+0xb4/0xec
  16     [   85.134694] Modules linked in: hci_uart bluetooth ecdh_generic ecc wlcore_sdio configfs
  17     [   85.143314] CPU: 0 PID: 27 Comm: kworker/u3:0 Not tainted 6.6.3-00021-gd62a2f068f92 #1
  18     [   85.151396] Hardware name: Freescale MXS (Device Tree)
  19     [   85.156679] Workqueue: hci0 hci_power_on [bluetooth]
  20     (...)
  21     [   85.191765]  uart_handle_cts_change from mxs_auart_irq_handle+0x380/0x3f4
  22     [   85.198787]  mxs_auart_irq_handle from __handle_irq_event_percpu+0x88/0x210
  23     (...)
  24
  25 Cc: stable@vger.kernel.org
  26 Fixes: 4d90bb147ef6 ("serial: core: Document and assert lock requirements for irq helpers")
  27 Reviewed-by: Frank Li <Frank.Li@nxp.com>
  28 Signed-off-by: Emil Kronborg <emil.kronborg@protonmail.com>
  29 Link: https://lore.kernel.org/r/20240320121530.11348-1-emil.kronborg@protonmail.com
  30 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  31 ---
  32  drivers/tty/serial/mxs-auart.c |    8 ++++++--
  33  1 file changed, 6 insertions(+), 2 deletions(-)
  34
  35 --- a/drivers/tty/serial/mxs-auart.c
  36 +++ b/drivers/tty/serial/mxs-auart.c
  37 @@ -1086,11 +1086,13 @@ static void mxs_auart_set_ldisc(struct u
  38
  39  static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
  40  {
  41 -       u32 istat;
  42 +       u32 istat, stat;
  43         struct mxs_auart_port *s = context;
  44         u32 mctrl_temp = s->mctrl_prev;
  45 -       u32 stat = mxs_read(s, REG_STAT);
  46
  47 +       uart_port_lock(&s->port);
  48 +
  49 +       stat = mxs_read(s, REG_STAT);
  50         istat = mxs_read(s, REG_INTR);
  51
  52         /* ack irq */
  53 @@ -1126,6 +1128,8 @@ static irqreturn_t mxs_auart_irq_handle(
  54                 istat &= ~AUART_INTR_TXIS;
  55         }
  56
  57 +       uart_port_unlock(&s->port);
  58 +
  59         return IRQ_HANDLED;
  60  }
  61