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Subject[PATCH 5/7] serial: stm32: Add support of TC bit status check
Date
Adds a check on the Transmission Complete bit status before closing the
com port. Prevents the port closure before the end of the transmission.
TC poll loop is moved from stm32_tx_dma_complete to stm32_shutdown
routine, in order to check TC before shutdown in both dma and
PIO tx modes.
TC clear is added in stm32_transmit_char routine, in order to be cleared
before transmitting in both dma and PIO tx modes.

Fixes: 3489187204eb ("serial: stm32: adding dma support")
Signed-off-by: Erwan Le Ray <erwan.leray@st.com>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 2e7757d..d603be9 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -290,21 +290,6 @@ static void stm32_tx_dma_complete(void *arg)
struct uart_port *port = arg;
struct stm32_port *stm32port = to_stm32_port(port);
struct stm32_usart_offsets *ofs = &stm32port->info->ofs;
- unsigned int isr;
- int ret;
-
- ret = readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr,
- isr,
- (isr & USART_SR_TC),
- 10, 100000);
-
- if (ret)
- dev_err(port->dev, "terminal count not set\n");
-
- if (ofs->icr == UNDEF_REG)
- stm32_clr_bits(port, ofs->isr, USART_SR_TC);
- else
- stm32_set_bits(port, ofs->icr, USART_CR_TC);

stm32_clr_bits(port, ofs->cr3, USART_CR3_DMAT);
stm32port->tx_dma_busy = false;
@@ -396,7 +381,6 @@ static void stm32_transmit_chars_dma(struct uart_port *port)
/* Issue pending DMA TX requests */
dma_async_issue_pending(stm32port->tx_ch);

- stm32_clr_bits(port, ofs->isr, USART_SR_TC);
stm32_set_bits(port, ofs->cr3, USART_CR3_DMAT);

xmit->tail = (xmit->tail + count) & (UART_XMIT_SIZE - 1);
@@ -425,6 +409,11 @@ static void stm32_transmit_chars(struct uart_port *port)
return;
}

+ if (ofs->icr == UNDEF_REG)
+ stm32_clr_bits(port, ofs->isr, USART_SR_TC);
+ else
+ stm32_set_bits(port, ofs->icr, USART_ICR_TCCF);
+
if (stm32_port->tx_ch)
stm32_transmit_chars_dma(port);
else
@@ -601,12 +590,21 @@ static void stm32_shutdown(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;
+ u32 val, isr;
+ int ret;

val = USART_CR1_TXEIE | USART_CR1_RXNEIE | USART_CR1_TE | USART_CR1_RE;
val |= BIT(cfg->uart_enable_bit);
if (stm32_port->fifoen)
val |= USART_CR1_FIFOEN;
+
+ ret = readl_relaxed_poll_timeout(port->membase + ofs->isr,
+ isr, (isr & USART_SR_TC),
+ 10, 100000);
+
+ if (ret)
+ dev_err(port->dev, "transmission complete not set\n");
+
stm32_clr_bits(port, ofs->cr1, val);

dev_pm_clear_wake_irq(port->dev);
--
1.9.1
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