target/linux/bcm27xx/patches-6.1/950-0698-serial-8250-Add-NOMSI-bug-for-bcm2835aux.patch

   1 From 501e87c5f421654e1bb6fd4a25de46420549cae8 Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.com>
   3 Date: Mon, 24 Apr 2023 11:48:31 +0100
   4 Subject: [PATCH] serial: 8250: Add NOMSI bug for bcm2835aux
   5
   6 The BCM2835 mini-UART has no modem status interrupt, causing all
   7 transmission to stop, never to use, if a speed change ever happens
   8 while the CTS signal is high.
   9
  10 Add a simple polling mechanism in order to allow recovery in that
  11 situation.
  12
  13 Signed-off-by: Phil Elwell <phil@raspberrypi.com>
  14 ---
  15  drivers/tty/serial/8250/8250.h            |  1 +
  16  drivers/tty/serial/8250/8250_bcm2835aux.c |  1 +
  17  drivers/tty/serial/8250/8250_core.c       | 15 +++++++++++++++
  18  drivers/tty/serial/8250/8250_port.c       |  9 +++++++++
  19  4 files changed, 26 insertions(+)
  20
  21 --- a/drivers/tty/serial/8250/8250.h
  22 +++ b/drivers/tty/serial/8250/8250.h
  23 @@ -93,6 +93,7 @@ struct serial8250_config {
  24  #define UART_BUG_THRE  BIT(3)  /* UART has buggy THRE reassertion */
  25  #define UART_BUG_PARITY        BIT(4)  /* UART mishandles parity if FIFO enabled */
  26  #define UART_BUG_TXRACE        BIT(5)  /* UART Tx fails to set remote DR */
  27 +#define UART_BUG_NOMSI BIT(6)  /* UART has no modem status interrupt */
  28
  29
  30  #ifdef CONFIG_SERIAL_8250_SHARE_IRQ
  31 --- a/drivers/tty/serial/8250/8250_bcm2835aux.c
  32 +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
  33 @@ -109,6 +109,7 @@ static int bcm2835aux_serial_probe(struc
  34                         UPF_SKIP_TEST | UPF_IOREMAP;
  35         up.port.rs485_config = serial8250_em485_config;
  36         up.port.rs485_supported = serial8250_em485_supported;
  37 +       up.bugs |= UART_BUG_NOMSI;
  38         up.rs485_start_tx = bcm2835aux_rs485_start_tx;
  39         up.rs485_stop_tx = bcm2835aux_rs485_stop_tx;
  40
  41 --- a/drivers/tty/serial/8250/8250_core.c
  42 +++ b/drivers/tty/serial/8250/8250_core.c
  43 @@ -252,6 +252,18 @@ static void serial8250_timeout(struct ti
  44         mod_timer(&up->timer, jiffies + uart_poll_timeout(&up->port));
  45  }
  46
  47 +static void serial8250_cts_poll_timeout(struct timer_list *t)
  48 +{
  49 +       struct uart_8250_port *up = from_timer(up, t, timer);
  50 +       unsigned long flags;
  51 +
  52 +       spin_lock_irqsave(&up->port.lock, flags);
  53 +       serial8250_modem_status(up);
  54 +       spin_unlock_irqrestore(&up->port.lock, flags);
  55 +       if (up->port.hw_stopped)
  56 +               mod_timer(&up->timer, jiffies + 1);
  57 +}
  58 +
  59  static void serial8250_backup_timeout(struct timer_list *t)
  60  {
  61         struct uart_8250_port *up = from_timer(up, t, timer);
  62 @@ -314,6 +326,9 @@ static void univ8250_setup_timer(struct
  63                           uart_poll_timeout(port) + HZ / 5);
  64         }
  65
  66 +       if (up->bugs & UART_BUG_NOMSI)
  67 +               up->timer.function = serial8250_cts_poll_timeout;
  68 +
  69         /*
  70          * If the "interrupt" for this port doesn't correspond with any
  71          * hardware interrupt, we use a timer-based system.  The original
  72 --- a/drivers/tty/serial/8250/8250_port.c
  73 +++ b/drivers/tty/serial/8250/8250_port.c
  74 @@ -1559,6 +1559,9 @@ static void serial8250_stop_tx(struct ua
  75                 serial_icr_write(up, UART_ACR, up->acr);
  76         }
  77         serial8250_rpm_put(up);
  78 +
  79 +       if (port->hw_stopped && (up->bugs & UART_BUG_NOMSI))
  80 +               mod_timer(&up->timer, jiffies + 1);
  81  }
  82
  83  static inline void __start_tx(struct uart_port *port)
  84 @@ -1669,6 +1672,9 @@ static void serial8250_start_tx(struct u
  85         struct uart_8250_port *up = up_to_u8250p(port);
  86         struct uart_8250_em485 *em485 = up->em485;
  87
  88 +       if (up->bugs & UART_BUG_NOMSI)
  89 +               del_timer(&up->timer);
  90 +
  91         if (!port->x_char && uart_circ_empty(&port->state->xmit))
  92                 return;
  93
  94 @@ -1889,6 +1895,9 @@ unsigned int serial8250_modem_status(str
  95                         uart_handle_cts_change(port, status & UART_MSR_CTS);
  96
  97                 wake_up_interruptible(&port->state->port.delta_msr_wait);
  98 +       } else if (up->bugs & UART_BUG_NOMSI && port->hw_stopped &&
  99 +                  status & UART_MSR_CTS) {
 100 +               uart_handle_cts_change(port, status & UART_MSR_CTS);
 101         }
 102
 103         return status;