diff options
| author | John Ogness <john.ogness@linutronix.de> | 2023-05-25 11:37:56 +0206 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-05-30 11:45:42 +0100 |
| commit | 87660fb4041f58d5fdfa58f4d3d35385dcc8320d (patch) | |
| tree | fb9200c1f32126bd54868b3436bff995873608b6 /drivers/tty | |
| parent | 51e45fba14bf08b66bca764a083c7f2e2ff62f01 (diff) | |
serial: 8250: lock port for rx_dma() callback
The rx_dma() callback (omap_8250_rx_dma) accesses UART_IER. This
register is modified twice by each console write
(serial8250_console_write()) under the port lock. However, not
all calls to the rx_dma() callback are under the port lock.
Add the missing port locking around rx_dma() callback calls. Add
lockdep notation to the omap_8250_rx_dma().
Note that this is not fixing a real problem because:
1. Currently DMA is forced off for 8250_omap consoles.
2. The serial devices are resumed before console printing is enabled.
However, adding this locking allows for clean locking semantics
for the rx_dma() callback so that lockdep can be used to identify
possible problems in the future. It also simplifies synchronization
of UART_IER in general by not needing to rely on implementation
details such as 1 and 2.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20230525093159.223817-6-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/8250/8250_omap.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index c17d98161d5e..3cb9cfa62331 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -728,8 +728,11 @@ static int omap_8250_startup(struct uart_port *port) priv->wer |= OMAP_UART_TX_WAKEUP_EN; serial_out(up, UART_OMAP_WER, priv->wer); - if (up->dma && !(priv->habit & UART_HAS_EFR2)) + if (up->dma && !(priv->habit & UART_HAS_EFR2)) { + spin_lock_irq(&port->lock); up->dma->rx_dma(up); + spin_unlock_irq(&port->lock); + } enable_irq(up->port.irq); @@ -1003,6 +1006,9 @@ static int omap_8250_rx_dma(struct uart_8250_port *p) unsigned long flags; u32 reg; + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&p->port.lock); + if (priv->rx_dma_broken) return -EINVAL; @@ -1736,8 +1742,11 @@ static int omap8250_runtime_resume(struct device *dev) if (up && omap8250_lost_context(up)) omap8250_restore_regs(up); - if (up && up->dma && up->dma->rxchan && !(priv->habit & UART_HAS_EFR2)) + if (up && up->dma && up->dma->rxchan && !(priv->habit & UART_HAS_EFR2)) { + spin_lock_irq(&up->port.lock); omap_8250_rx_dma(up); + spin_unlock_irq(&up->port.lock); + } priv->latency = priv->calc_latency; schedule_work(&priv->qos_work); |