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tty: serial: msm: Support sysrq on uartDM devices 

To properly support sysrq on uartDM hardware we need to properly
handle break characters. With the DM hardware the fifo can pack 4
characters at a time, where a break is indicated by an all zero
byte. Unfortunately, we can't differentiate between an all zero
byte for a break and an all zero byte of data, so try and do as
best we can. First unmask the RX break start interrupt and record
the interrupt when it arrives. Then while processing the fifo,
detect the break by searching for an all zero character as long
as we recently received an RX break start interrupt. This should
make sysrq work fairly well.

Cc: Frank Rowand <frank.rowand@sonymobile.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Stephen Boyd 2014-10-29 11:14:38 -07:00 committed by Greg Kroah-Hartman
parent 660beb0e94
commit 0896d4d4fb
2 changed files with 34 additions and 11 deletions
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43
drivers/tty/serial/msm_serial.c
View File

@ -54,6 +54,7 @@ struct msm_port {
unsigned int imr;
int is_uartdm;
unsigned int old_snap_state;
bool break_detected;
};
static inline void wait_for_xmitr(struct uart_port *port)
@ -126,23 +127,38 @@ static void handle_rx_dm(struct uart_port *port, unsigned int misr)
while (count > 0) {
unsigned char buf[4];
int sysrq, r_count, i;
sr = msm_read(port, UART_SR);
if ((sr & UART_SR_RX_READY) == 0) {
msm_port->old_snap_state -= count;
break;
}
ioread32_rep(port->membase + UARTDM_RF, buf, 1);
if (sr & UART_SR_RX_BREAK) {
port->icount.brk++;
if (uart_handle_break(port))
continue;
} else if (sr & UART_SR_PAR_FRAME_ERR)
port->icount.frame++;
/* TODO: handle sysrq */
tty_insert_flip_string(tport, buf, min(count, 4));
count -= 4;
ioread32_rep(port->membase + UARTDM_RF, buf, 1);
r_count = min_t(int, count, sizeof(buf));
for (i = 0; i < r_count; i++) {
char flag = TTY_NORMAL;
if (msm_port->break_detected && buf[i] == 0) {
port->icount.brk++;
flag = TTY_BREAK;
msm_port->break_detected = false;
if (uart_handle_break(port))
continue;
}
if (!(port->read_status_mask & UART_SR_RX_BREAK))
flag = TTY_NORMAL;
spin_unlock(&port->lock);
sysrq = uart_handle_sysrq_char(port, buf[i]);
spin_lock(&port->lock);
if (!sysrq)
tty_insert_flip_char(tport, buf[i], flag);
}
count -= r_count;
}
spin_unlock(&port->lock);
@ -291,6 +307,11 @@ static irqreturn_t msm_irq(int irq, void *dev_id)
misr = msm_read(port, UART_MISR);
msm_write(port, 0, UART_IMR); /* disable interrupt */
if (misr & UART_IMR_RXBREAK_START) {
msm_port->break_detected = true;
msm_write(port, UART_CR_CMD_RESET_RXBREAK_START, UART_CR);
}
if (misr & (UART_IMR_RXLEV | UART_IMR_RXSTALE)) {
if (msm_port->is_uartdm)
handle_rx_dm(port, misr);
@ -496,7 +517,7 @@ static int msm_startup(struct uart_port *port)
/* turn on RX and CTS interrupts */
msm_port->imr = UART_IMR_RXLEV | UART_IMR_RXSTALE |
UART_IMR_CURRENT_CTS;
UART_IMR_CURRENT_CTS | UART_IMR_RXBREAK_START;
if (msm_port->is_uartdm) {
msm_write(port, 0xFFFFFF, UARTDM_DMRX);

2
drivers/tty/serial/msm_serial.h
View File

@ -65,6 +65,7 @@
#define UART_CR_TX_ENABLE (1 << 2)
#define UART_CR_RX_DISABLE (1 << 1)
#define UART_CR_RX_ENABLE (1 << 0)
#define UART_CR_CMD_RESET_RXBREAK_START ((1 << 11) | (2 << 4))
#define UART_IMR 0x0014
#define UART_IMR_TXLEV (1 << 0)
@ -72,6 +73,7 @@
#define UART_IMR_RXLEV (1 << 4)
#define UART_IMR_DELTA_CTS (1 << 5)
#define UART_IMR_CURRENT_CTS (1 << 6)
#define UART_IMR_RXBREAK_START (1 << 10)
#define UART_IPR_RXSTALE_LAST 0x20
#define UART_IPR_STALE_LSB 0x1F