104 lines
3.6 KiB
Diff
104 lines
3.6 KiB
Diff
From 501e87c5f421654e1bb6fd4a25de46420549cae8 Mon Sep 17 00:00:00 2001
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From: Phil Elwell <phil@raspberrypi.com>
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Date: Mon, 24 Apr 2023 11:48:31 +0100
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Subject: [PATCH] serial: 8250: Add NOMSI bug for bcm2835aux
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The BCM2835 mini-UART has no modem status interrupt, causing all
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transmission to stop, never to use, if a speed change ever happens
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while the CTS signal is high.
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Add a simple polling mechanism in order to allow recovery in that
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situation.
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Signed-off-by: Phil Elwell <phil@raspberrypi.com>
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---
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drivers/tty/serial/8250/8250.h | 1 +
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drivers/tty/serial/8250/8250_bcm2835aux.c | 1 +
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drivers/tty/serial/8250/8250_core.c | 15 +++++++++++++++
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drivers/tty/serial/8250/8250_port.c | 9 +++++++++
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4 files changed, 26 insertions(+)
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--- a/drivers/tty/serial/8250/8250.h
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+++ b/drivers/tty/serial/8250/8250.h
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@@ -92,6 +92,7 @@ struct serial8250_config {
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#define UART_BUG_NOMSR BIT(2) /* UART has buggy MSR status bits (Au1x00) */
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#define UART_BUG_THRE BIT(3) /* UART has buggy THRE reassertion */
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#define UART_BUG_TXRACE BIT(5) /* UART Tx fails to set remote DR */
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+#define UART_BUG_NOMSI BIT(6) /* UART has no modem status interrupt */
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#ifdef CONFIG_SERIAL_8250_SHARE_IRQ
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--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
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+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
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@@ -109,6 +109,7 @@ static int bcm2835aux_serial_probe(struc
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UPF_SKIP_TEST | UPF_IOREMAP;
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up.port.rs485_config = serial8250_em485_config;
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up.port.rs485_supported = serial8250_em485_supported;
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+ up.bugs |= UART_BUG_NOMSI;
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up.rs485_start_tx = bcm2835aux_rs485_start_tx;
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up.rs485_stop_tx = bcm2835aux_rs485_stop_tx;
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--- a/drivers/tty/serial/8250/8250_core.c
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+++ b/drivers/tty/serial/8250/8250_core.c
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@@ -252,6 +252,18 @@ static void serial8250_timeout(struct ti
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mod_timer(&up->timer, jiffies + uart_poll_timeout(&up->port));
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}
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+static void serial8250_cts_poll_timeout(struct timer_list *t)
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+{
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+ struct uart_8250_port *up = from_timer(up, t, timer);
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+ unsigned long flags;
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+
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+ spin_lock_irqsave(&up->port.lock, flags);
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+ serial8250_modem_status(up);
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+ spin_unlock_irqrestore(&up->port.lock, flags);
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+ if (up->port.hw_stopped)
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+ mod_timer(&up->timer, jiffies + 1);
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+}
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+
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static void serial8250_backup_timeout(struct timer_list *t)
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{
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struct uart_8250_port *up = from_timer(up, t, timer);
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@@ -314,6 +326,9 @@ static void univ8250_setup_timer(struct
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uart_poll_timeout(port) + HZ / 5);
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}
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+ if (up->bugs & UART_BUG_NOMSI)
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+ up->timer.function = serial8250_cts_poll_timeout;
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+
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/*
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* If the "interrupt" for this port doesn't correspond with any
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* hardware interrupt, we use a timer-based system. The original
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--- a/drivers/tty/serial/8250/8250_port.c
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+++ b/drivers/tty/serial/8250/8250_port.c
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@@ -1559,6 +1559,9 @@ static void serial8250_stop_tx(struct ua
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serial_icr_write(up, UART_ACR, up->acr);
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}
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serial8250_rpm_put(up);
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+
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+ if (port->hw_stopped && (up->bugs & UART_BUG_NOMSI))
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+ mod_timer(&up->timer, jiffies + 1);
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}
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static inline void __start_tx(struct uart_port *port)
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@@ -1669,6 +1672,9 @@ static void serial8250_start_tx(struct u
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struct uart_8250_port *up = up_to_u8250p(port);
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struct uart_8250_em485 *em485 = up->em485;
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+ if (up->bugs & UART_BUG_NOMSI)
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+ del_timer(&up->timer);
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+
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if (!port->x_char && uart_circ_empty(&port->state->xmit))
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return;
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@@ -1889,6 +1895,9 @@ unsigned int serial8250_modem_status(str
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uart_handle_cts_change(port, status & UART_MSR_CTS);
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wake_up_interruptible(&port->state->port.delta_msr_wait);
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+ } else if (up->bugs & UART_BUG_NOMSI && port->hw_stopped &&
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+ status & UART_MSR_CTS) {
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+ uart_handle_cts_change(port, status & UART_MSR_CTS);
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}
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return status;
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