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Subject[PATCH 5/7] tty: serial: lantiq: Convert global lock to per device lock
Date
Previous implementation uses one global lock to protect the resource.
If the serial driver have multiple entries, this kind of lock will
slow down the performance.
Add the lock at device level. This will lock only when the function
calling only to the same device.
So that it can avoid useless lock protection.

Signed-off-by: Songjun Wu <songjun.wu@linux.intel.com>
---

drivers/tty/serial/lantiq.c | 51 ++++++++++++++++++++++++++++++---------------
1 file changed, 34 insertions(+), 17 deletions(-)

diff --git a/drivers/tty/serial/lantiq.c b/drivers/tty/serial/lantiq.c
index 1127586dbc94..72aab1b05265 100644
--- a/drivers/tty/serial/lantiq.c
+++ b/drivers/tty/serial/lantiq.c
@@ -107,7 +107,6 @@
static void lqasc_tx_chars(struct uart_port *port);
static struct ltq_uart_port *lqasc_port[MAXPORTS];
static struct uart_driver lqasc_reg;
-static DEFINE_SPINLOCK(ltq_asc_lock);

struct ltq_uart_port {
struct uart_port port;
@@ -118,6 +117,7 @@ struct ltq_uart_port {
unsigned int tx_irq;
unsigned int rx_irq;
unsigned int err_irq;
+ spinlock_t lock; /* exclusive access for multi core */
};

static inline struct ltq_uart_port *to_ltq_uart_port(struct uart_port *port)
@@ -133,10 +133,11 @@ static void lqasc_stop_tx(struct uart_port *port)
static void lqasc_start_tx(struct uart_port *port)
{
unsigned long flags;
- spin_lock_irqsave(&ltq_asc_lock, flags);
+ struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+ spin_lock_irqsave(&ltq_port->lock, flags);
lqasc_tx_chars(port);
- spin_unlock_irqrestore(&ltq_asc_lock, flags);
- return;
+ spin_unlock_irqrestore(&ltq_port->lock, flags);
}

static void lqasc_stop_rx(struct uart_port *port)
@@ -238,10 +239,14 @@ static irqreturn_t lqasc_tx_int(int irq, void *_port)
{
unsigned long flags;
struct uart_port *port = (struct uart_port *)_port;
- spin_lock_irqsave(&ltq_asc_lock, flags);
+ struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+ spin_lock_irqsave(&ltq_port->lock, flags);
writel(ASC_IRNCR_TIR, port->membase + LTQ_ASC_IRNCR);
- spin_unlock_irqrestore(&ltq_asc_lock, flags);
+ spin_unlock_irqrestore(&ltq_port->lock, flags);
+
lqasc_start_tx(port);
+
return IRQ_HANDLED;
}

@@ -250,8 +255,9 @@ static irqreturn_t lqasc_err_int(int irq, void *_port)
unsigned long flags;
u32 stat;
struct uart_port *port = (struct uart_port *)_port;
+ struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);

- spin_lock_irqsave(&ltq_asc_lock, flags);
+ spin_lock_irqsave(&ltq_port->lock, flags);
/* clear any pending interrupts */
writel(ASC_IRNCR_EIR, port->membase + LTQ_ASC_IRNCR);
stat = readl(port->membase + LTQ_ASC_STATE);
@@ -266,7 +272,7 @@ static irqreturn_t lqasc_err_int(int irq, void *_port)
port->icount.overrun++;
}
asc_w32_mask(0, ASCWHBSTATE_CLRALL, port->membase + LTQ_ASC_WHBSTATE);
- spin_unlock_irqrestore(&ltq_asc_lock, flags);
+ spin_unlock_irqrestore(&ltq_port->lock, flags);

return IRQ_HANDLED;
}
@@ -275,10 +281,13 @@ static irqreturn_t lqasc_rx_int(int irq, void *_port)
{
unsigned long flags;
struct uart_port *port = (struct uart_port *)_port;
- spin_lock_irqsave(&ltq_asc_lock, flags);
+ struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+
+ spin_lock_irqsave(&ltq_port->lock, flags);
writel(ASC_IRNCR_RIR, port->membase + LTQ_ASC_IRNCR);
lqasc_rx_chars(port);
- spin_unlock_irqrestore(&ltq_asc_lock, flags);
+ spin_unlock_irqrestore(&ltq_port->lock, flags);
+
return IRQ_HANDLED;
}

@@ -309,11 +318,13 @@ lqasc_startup(struct uart_port *port)
{
struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
int retval;
+ unsigned long flags;

if (!IS_ERR(ltq_port->clk))
clk_enable(ltq_port->clk);
port->uartclk = clk_get_rate(ltq_port->fpiclk);

+ spin_lock_irqsave(&ltq_port->lock, flags);
asc_w32_mask(ASCCLC_DISS | ASCCLC_RMCMASK, (1 << ASCCLC_RMCOFFSET),
port->membase + LTQ_ASC_CLC);

@@ -330,6 +341,7 @@ lqasc_startup(struct uart_port *port)
wmb();
asc_w32_mask(0, ASCCON_M_8ASYNC | ASCCON_FEN | ASCCON_TOEN |
ASCCON_ROEN, port->membase + LTQ_ASC_CON);
+ spin_unlock_irqrestore(&ltq_port->lock, flags);

retval = request_irq(ltq_port->tx_irq, lqasc_tx_int,
0, "asc_tx", port);
@@ -410,6 +422,7 @@ static void lqasc_set_termios(struct uart_port *port,
unsigned long flags;
u32 fdv = 0;
u32 reload = 0;
+ struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);

cflag = new->c_cflag;
iflag = new->c_iflag;
@@ -463,7 +476,7 @@ static void lqasc_set_termios(struct uart_port *port,
/* set error signals - framing, parity and overrun, enable receiver */
con |= ASCCON_FEN | ASCCON_TOEN | ASCCON_ROEN;

- spin_lock_irqsave(&ltq_asc_lock, flags);
+ spin_lock_irqsave(&ltq_port->lock, flags);

/* set up CON */
asc_w32_mask(0, con, port->membase + LTQ_ASC_CON);
@@ -490,7 +503,7 @@ static void lqasc_set_termios(struct uart_port *port,
/* enable rx */
writel(ASCWHBSTATE_SETREN, port->membase + LTQ_ASC_WHBSTATE);

- spin_unlock_irqrestore(&ltq_asc_lock, flags);
+ spin_unlock_irqrestore(&ltq_port->lock, flags);

/* Don't rewrite B0 */
if (tty_termios_baud_rate(new))
@@ -604,16 +617,14 @@ static void lqasc_console_putchar(struct uart_port *port, int ch)
static void lqasc_serial_port_write(struct uart_port *port, const char *s,
u_int count)
{
- unsigned long flags;
-
- spin_lock_irqsave(&ltq_asc_lock, flags);
uart_console_write(port, s, count, lqasc_console_putchar);
- spin_unlock_irqrestore(&ltq_asc_lock, flags);
}

static void lqasc_console_write(struct console *co, const char *s, u_int count)
{
+ unsigned long flags;
struct ltq_uart_port *ltq_port;
+ struct uart_port *port;

if (co->index >= MAXPORTS)
return;
@@ -622,7 +633,11 @@ static void lqasc_console_write(struct console *co, const char *s, u_int count)
if (!ltq_port)
return;

- lqasc_serial_port_write(&ltq_port->port, s, count);
+ port = &ltq_port->port;
+
+ spin_lock_irqsave(&ltq_port->lock, flags);
+ lqasc_serial_port_write(port, s, count);
+ spin_unlock_irqrestore(&ltq_port->lock, flags);
}

static int __init lqasc_console_setup(struct console *co, char *options)
@@ -760,6 +775,8 @@ static int __init lqasc_probe(struct platform_device *pdev)
ltq_port->rx_irq = irqres[1].start;
ltq_port->err_irq = irqres[2].start;

+ spin_lock_init(&ltq_port->lock);
+
lqasc_port[line] = ltq_port;
platform_set_drvdata(pdev, ltq_port);

--
2.11.0
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