linux-kernel - [PATCH v2 2/6] serial: stm32: use DMAT as a configuration bit

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Date:   Tue, 8 Aug 2023 18:19:02 +0200
From:   Valentin Caron <valentin.caron@...s.st.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Jiri Slaby <jirislaby@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Amelie Delaunay <amelie.delaunay@...s.st.com>,
        <linux-serial@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        Valentin Caron <valentin.caron@...s.st.com>
Subject: [PATCH v2 2/6] 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@...s.st.com>
---
 drivers/tty/serial/stm32-usart.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 2f9672ba4ed3..a1585aa1ceb0 100644
--- 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,
-- 
2.25.1