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Subject[PATCH 06/13] serial: stm32: fix wake-up flag handling
Date
This patch fixes several issue with wake-up handling:
- the WUF irq is handled several times at wake-up
- the USART is disabled / enabled at suspend to set wake-up flag.
It can cause glitches during RX.

This patch fix those issues:
- clear wake-up flag and disable wake-up irq in WUF irq handling
- enable wake-up from low power on start bit detection at port
configuration
- Unmask the wake-up flag irq at suspend and mask it at resume

In addition, pm_wakeup_event handling is moved from receice_chars to WUF
irq handling.

Fixes: 270e5a74fe4c ("serial: stm32: add wakeup mechanism")
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 524c55751023..14011183edfe 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -218,9 +218,6 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
u32 sr;
char flag;

- if (irqd_is_wakeup_set(irq_get_irq_data(port->irq)))
- pm_wakeup_event(tport->tty->dev, 0);
-
if (threaded)
spin_lock_irqsave(&port->lock, flags);
else
@@ -463,6 +460,7 @@ static void stm32_usart_transmit_chars(struct uart_port *port)
static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
{
struct uart_port *port = ptr;
+ struct tty_port *tport = &port->state->port;
struct stm32_port *stm32_port = to_stm32_port(port);
struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
u32 sr;
@@ -473,9 +471,14 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
writel_relaxed(USART_ICR_RTOCF,
port->membase + ofs->icr);

- if ((sr & USART_SR_WUF) && ofs->icr != UNDEF_REG)
+ if ((sr & USART_SR_WUF) && ofs->icr != UNDEF_REG) {
+ /* Clear wake up flag and disable wake up interrupt */
writel_relaxed(USART_ICR_WUCF,
port->membase + ofs->icr);
+ stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_WUFIE);
+ if (irqd_is_wakeup_set(irq_get_irq_data(port->irq)))
+ pm_wakeup_event(tport->tty->dev, 0);
+ }

if ((sr & USART_SR_RXNE) && !(stm32_port->rx_ch))
stm32_usart_receive_chars(port, false);
@@ -901,6 +904,12 @@ static void stm32_usart_set_termios(struct uart_port *port,
cr1 &= ~(USART_CR1_DEDT_MASK | USART_CR1_DEAT_MASK);
}

+ /* Configure wake up from low power on start bit detection */
+ if (stm32_port->wakeirq > 0) {
+ cr3 &= ~USART_CR3_WUS_MASK;
+ cr3 |= USART_CR3_WUS_START_BIT;
+ }
+
writel_relaxed(cr3, port->membase + ofs->cr3);
writel_relaxed(cr2, port->membase + ofs->cr2);
writel_relaxed(cr1, port->membase + ofs->cr1);
@@ -1479,23 +1488,20 @@ static void __maybe_unused stm32_usart_serial_en_wakeup(struct uart_port *port,
{
struct stm32_port *stm32_port = to_stm32_port(port);
struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
- struct stm32_usart_config *cfg = &stm32_port->info->cfg;
- u32 val;

if (stm32_port->wakeirq <= 0)
return;

+ /*
+ * Enable low-power wake-up and wake-up irq if argument is set to
+ * "enable", disable low-power wake-up and wake-up irq otherwise
+ */
if (enable) {
- stm32_usart_clr_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
stm32_usart_set_bits(port, ofs->cr1, USART_CR1_UESM);
- val = readl_relaxed(port->membase + ofs->cr3);
- val &= ~USART_CR3_WUS_MASK;
- /* Enable Wake up interrupt from low power on start bit */
- val |= USART_CR3_WUS_START_BIT | USART_CR3_WUFIE;
- writel_relaxed(val, port->membase + ofs->cr3);
- stm32_usart_set_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
+ stm32_usart_set_bits(port, ofs->cr3, USART_CR3_WUFIE);
} else {
stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_UESM);
+ stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_WUFIE);
}
}

--
2.17.1
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