From: Marek Vasut marex@denx.de
[ Upstream commit d7c76716169ddc37cf6316ff381d34ea807fbfd7 ]
In case the RS485 mode is emulated using GPIO RTS, use the TC interrupt to deassert the GPIO RTS, otherwise the GPIO RTS stays asserted after a transmission ended and the RS485 cannot work.
Signed-off-by: Marek Vasut marex@denx.de Cc: Alexandre Torgue alexandre.torgue@foss.st.com Cc: Erwan Le Ray erwan.leray@foss.st.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jean Philippe Romain jean-philippe.romain@foss.st.com Cc: Valentin Caron valentin.caron@foss.st.com Cc: linux-arm-kernel@lists.infradead.org Cc: linux-stm32@st-md-mailman.stormreply.com To: linux-serial@vger.kernel.org Link: https://lore.kernel.org/r/20220430162845.244655-2-marex@denx.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/stm32-usart.c | 42 ++++++++++++++++++++++++++++++-- drivers/tty/serial/stm32-usart.h | 1 + 2 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index f2cef5f7ae5a..86f044a96de1 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -314,6 +314,14 @@ static void stm32_usart_tx_interrupt_enable(struct uart_port *port) stm32_usart_set_bits(port, ofs->cr1, USART_CR1_TXEIE); }
+static void stm32_usart_tc_interrupt_enable(struct uart_port *port) +{ + struct stm32_port *stm32_port = to_stm32_port(port); + const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; + + stm32_usart_set_bits(port, ofs->cr1, USART_CR1_TCIE); +} + static void stm32_usart_tx_interrupt_disable(struct uart_port *port) { struct stm32_port *stm32_port = to_stm32_port(port); @@ -325,6 +333,14 @@ static void stm32_usart_tx_interrupt_disable(struct uart_port *port) stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_TXEIE); }
+static void stm32_usart_tc_interrupt_disable(struct uart_port *port) +{ + struct stm32_port *stm32_port = to_stm32_port(port); + const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; + + stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_TCIE); +} + static void stm32_usart_rs485_rts_enable(struct uart_port *port) { struct stm32_port *stm32_port = to_stm32_port(port); @@ -462,6 +478,13 @@ static void stm32_usart_transmit_chars(struct uart_port *port) u32 isr; int ret;
+ if (!stm32_port->hw_flow_control && + port->rs485.flags & SER_RS485_ENABLED) { + stm32_port->txdone = false; + stm32_usart_tc_interrupt_disable(port); + stm32_usart_rs485_rts_enable(port); + } + if (port->x_char) { if (stm32_port->tx_dma_busy) stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); @@ -501,8 +524,14 @@ static void stm32_usart_transmit_chars(struct uart_port *port) if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) uart_write_wakeup(port);
- if (uart_circ_empty(xmit)) + if (uart_circ_empty(xmit)) { stm32_usart_tx_interrupt_disable(port); + if (!stm32_port->hw_flow_control && + port->rs485.flags & SER_RS485_ENABLED) { + stm32_port->txdone = true; + stm32_usart_tc_interrupt_enable(port); + } + } }
static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) @@ -515,6 +544,13 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
sr = readl_relaxed(port->membase + ofs->isr);
+ if (!stm32_port->hw_flow_control && + port->rs485.flags & SER_RS485_ENABLED && + (sr & USART_SR_TC)) { + stm32_usart_tc_interrupt_disable(port); + stm32_usart_rs485_rts_disable(port); + } + if ((sr & USART_SR_RTOF) && ofs->icr != UNDEF_REG) writel_relaxed(USART_ICR_RTOCF, port->membase + ofs->icr); @@ -612,8 +648,10 @@ static void stm32_usart_start_tx(struct uart_port *port) { struct circ_buf *xmit = &port->state->xmit;
- if (uart_circ_empty(xmit) && !port->x_char) + if (uart_circ_empty(xmit) && !port->x_char) { + stm32_usart_rs485_rts_disable(port); return; + }
stm32_usart_rs485_rts_enable(port);
diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h index 07ac291328cd..ad6335155de2 100644 --- a/drivers/tty/serial/stm32-usart.h +++ b/drivers/tty/serial/stm32-usart.h @@ -267,6 +267,7 @@ struct stm32_port { bool hw_flow_control; bool swap; /* swap RX & TX pins */ bool fifoen; + bool txdone; int rxftcfg; /* RX FIFO threshold CFG */ int txftcfg; /* TX FIFO threshold CFG */ bool wakeup_src;