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Subject[PATCH 4/4] serial: 8250_dw: Rework ->serial_out() LCR write retry logic
Date
Currently dw8250_verify_write() (was dw8250_check_lcr()) nullifies the
benefit from differentiated ->serial_out() by having big if tree to
select correct write type.

Rework the logic such that the LCR write can be retried within the
relevant ->serial_out() handler:
1. Move retries counter on the caller level and pass as pointer to
dw8250_verify_write()
2. Make dw8250_verify_write() return bool
3. Retry the write on caller level (if needed)

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
drivers/tty/serial/8250/8250_dw.c | 59 ++++++++++++++++++-------------
1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index fc367d44f86d..f6846363341b 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -92,41 +92,36 @@ static void dw8250_force_idle(struct uart_port *p)
* UART_16550_COMPATIBLE=NO or version prior to introducing that option).
* If BUSY is set while writing to LCR register, the write is ignored and
* needs to be retries.
+ *
+ * Returns: false if the caller should retry the write.
*/
-static void dw8250_verify_write(struct uart_port *p, int offset, int value)
+static bool dw8250_verify_write(struct uart_port *p, int offset, int value,
+ unsigned int *retries)
{
- void __iomem *reg_offset = p->membase + (offset << p->regshift);
struct dw8250_data *d = to_dw8250_data(p->private_data);
- int tries = 1000;
+ unsigned int lcr;

if ((offset != UART_LCR) || !d->uart_16550_compatible)
- return;
+ return true;

/* Make sure LCR write wasn't ignored */
- while (tries--) {
- unsigned int lcr = p->serial_in(p, offset);
+ lcr = p->serial_in(p, offset);

- if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
- return;
+ if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
+ return true;

- dw8250_force_idle(p);
+ dw8250_force_idle(p);

-#ifdef CONFIG_64BIT
- if (p->type == PORT_OCTEON)
- __raw_writeq(value & 0xff, reg_offset);
- else
-#endif
- if (p->iotype == UPIO_MEM32)
- writel(value, reg_offset);
- else if (p->iotype == UPIO_MEM32BE)
- iowrite32be(value, reg_offset);
- else
- writeb(value, reg_offset);
+ if (*retries) {
+ *retries -= 1;
+ return false;
}
+
/*
* FIXME: this deadlocks if port->lock is already held
* dev_err(p->dev, "Couldn't set LCR to %d\n", value);
*/
+ return true;
}

/* Returns once the transmitter is empty or we run out of retries */
@@ -155,9 +150,13 @@ static void dw8250_tx_wait_empty(struct uart_port *p)

static void dw8250_serial_out(struct uart_port *p, int offset, int value)
{
+ unsigned int retries = 1000;
+
+retry:
writeb(value, p->membase + (offset << p->regshift));

- dw8250_verify_write(p, offset, value);
+ if (!dw8250_verify_write(p, offset, value, &retries))
+ goto retry;
}

static void dw8250_serial_out38x(struct uart_port *p, int offset, int value)
@@ -188,20 +187,29 @@ static unsigned int dw8250_serial_inq(struct uart_port *p, int offset)

static void dw8250_serial_outq(struct uart_port *p, int offset, int value)
{
+ unsigned int retries = 1000;
+
value &= 0xff;
+
+retry:
__raw_writeq(value, p->membase + (offset << p->regshift));
/* Read back to ensure register write ordering. */
__raw_readq(p->membase + (UART_LCR << p->regshift));

- dw8250_verify_write(p, offset, value);
+ if (!dw8250_verify_write(p, offset, value, &retries))
+ goto retry;
}
#endif /* CONFIG_64BIT */

static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
{
+ unsigned int retries = 1000;
+
+retry:
writel(value, p->membase + (offset << p->regshift));

- dw8250_verify_write(p, offset, value);
+ if (!dw8250_verify_write(p, offset, value, &retries))
+ goto retry;
}

static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)
@@ -213,10 +221,13 @@ static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)

static void dw8250_serial_out32be(struct uart_port *p, int offset, int value)
{
+ unsigned int retries = 1000;

+retry:
iowrite32be(value, p->membase + (offset << p->regshift));

- dw8250_verify_write(p, offset, value);
+ if (!dw8250_verify_write(p, offset, value, &retries))
+ goto retry;
}

static unsigned int dw8250_serial_in32be(struct uart_port *p, int offset)
--
2.30.2
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