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serial: fsl_lpuart: add sysrq support when using dma 

Add handling of magic sysrq keys when using dma/edma.

Tested by sending BREAK followed by a sysrq command inside
a 5 secs time window, by:

echo 1 > /proc/sys/kernel/sysrq

BREAK + h, t, e, b, c

Tested also sending a command after 5 secs after BREAK, that's
properly ignored.

Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
Link: https://lore.kernel.org/r/20201004161144.1307174-1-angelo.dureghello@timesys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Angelo Dureghello 2020-10-04 18:11:44 +02:00 committed by Greg Kroah-Hartman
parent bfeb28539d
commit f4eef224a0
1 changed files with 57 additions and 0 deletions
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57
drivers/tty/serial/fsl_lpuart.c
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@ -976,6 +976,15 @@ static irqreturn_t lpuart_int(int irq, void *dev_id)
sts = readb(sport->port.membase + UARTSR1);
/* SysRq, using dma, check for linebreak by framing err. */
if (sts & UARTSR1_FE && sport->lpuart_dma_rx_use) {
readb(sport->port.membase + UARTDR);
uart_handle_break(&sport->port);
/* linebreak produces some garbage, removing it */
writeb(UARTCFIFO_RXFLUSH, sport->port.membase + UARTCFIFO);
return IRQ_HANDLED;
}
if (sts & UARTSR1_RDRF && !sport->lpuart_dma_rx_use)
lpuart_rxint(sport);
@ -1004,6 +1013,37 @@ static irqreturn_t lpuart32_int(int irq, void *dev_id)
return IRQ_HANDLED;
}
static inline void lpuart_handle_sysrq_chars(struct uart_port *port,
unsigned char *p, int count)
{
while (count--) {
if (*p && uart_handle_sysrq_char(port, *p))
return;
p++;
}
}
static void lpuart_handle_sysrq(struct lpuart_port *sport)
{
struct circ_buf *ring = &sport->rx_ring;
int count;
if (ring->head < ring->tail) {
count = sport->rx_sgl.length - ring->tail;
lpuart_handle_sysrq_chars(&sport->port,
ring->buf + ring->tail, count);
ring->tail = 0;
}
if (ring->head > ring->tail) {
count = ring->head - ring->tail;
lpuart_handle_sysrq_chars(&sport->port,
ring->buf + ring->tail, count);
ring->tail = ring->head;
}
}
static void lpuart_copy_rx_to_tty(struct lpuart_port *sport)
{
struct tty_port *port = &sport->port.state->port;
@ -1090,6 +1130,15 @@ static void lpuart_copy_rx_to_tty(struct lpuart_port *sport)
*/
ring->head = sport->rx_sgl.length - state.residue;
BUG_ON(ring->head > sport->rx_sgl.length);
/*
* Silent handling of keys pressed in the sysrq timeframe
*/
if (sport->port.sysrq) {
lpuart_handle_sysrq(sport);
goto exit;
}
/*
* At this point ring->head may point to the first byte right after the
* last byte of the dma buffer:
@ -1121,6 +1170,7 @@ static void lpuart_copy_rx_to_tty(struct lpuart_port *sport)
sport->port.icount.rx += count;
}
exit:
dma_sync_sg_for_device(chan->device->dev, &sport->rx_sgl, 1,
DMA_FROM_DEVICE);
@ -1557,6 +1607,7 @@ static void lpuart_tx_dma_startup(struct lpuart_port *sport)
static void lpuart_rx_dma_startup(struct lpuart_port *sport)
{
int ret;
unsigned char cr3;
if (!sport->dma_rx_chan)
goto err;
@ -1573,6 +1624,12 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport)
sport->lpuart_dma_rx_use = true;
rx_dma_timer_init(sport);
if (sport->port.has_sysrq) {
cr3 = readb(sport->port.membase + UARTCR3);
cr3 |= UARTCR3_FEIE;
writeb(cr3, sport->port.membase + UARTCR3);
}
return;
err: