serial: stm32: use DMAT as a configuration bit

DMAT is a configuration bit so it should be set at the startup of uart
port and not when a DMA transfer begins.

This patch move set of DMAT into set_termios and remove DMAT reset except
in shutdown.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20230808161906.178996-3-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 2f9672b..a1585aa 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -510,10 +510,8 @@ static void stm32_usart_tx_dma_complete(void *arg)
 {
        struct uart_port *port = arg;
        struct stm32_port *stm32port = to_stm32_port(port);
-       const struct stm32_usart_offsets *ofs = &stm32port->info->ofs;
        unsigned long flags;
 
-       stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT);
        stm32_usart_tx_dma_terminate(stm32port);
 
        /* Let's see if we have pending data to send */
@@ -602,7 +600,6 @@ static void stm32_usart_transmit_chars_pio(struct uart_port *port)
 static void stm32_usart_transmit_chars_dma(struct uart_port *port)
 {
        struct stm32_port *stm32port = to_stm32_port(port);
-       const struct stm32_usart_offsets *ofs = &stm32port->info->ofs;
        struct circ_buf *xmit = &port->state->xmit;
        struct dma_async_tx_descriptor *desc = NULL;
        unsigned int count;
@@ -667,8 +664,6 @@ static void stm32_usart_transmit_chars_dma(struct uart_port *port)
        /* Issue pending DMA TX requests */
        dma_async_issue_pending(stm32port->tx_ch);
 
-       stm32_usart_set_bits(port, ofs->cr3, USART_CR3_DMAT);
-
        uart_xmit_advance(port, count);
 
        return;
@@ -1270,6 +1265,9 @@ static void stm32_usart_set_termios(struct uart_port *port,
                cr3 |= USART_CR3_DDRE;
        }
 
+       if (stm32_port->tx_ch)
+               cr3 |= USART_CR3_DMAT;
+
        if (rs485conf->flags & SER_RS485_ENABLED) {
                stm32_usart_config_reg_rs485(&cr1, &cr3,
                                             rs485conf->delay_rts_before_send,