From 5d9176edacc29cadb9a0b52c8aaba67ce5ff4ed4 Mon Sep 17 00:00:00 2001 From: Erwan Le Ray Date: Tue, 18 Jun 2019 12:02:23 +0200 Subject: serial: stm32: update PIO transmission Improves PIO transmission: - Replaces the FIFO filling per character by a filling per blocks of characters, which provides better performances - Replaces the active waiting loop by TX empty interrupt dynamic handling. TXE interrupt is now enabled when data has to be sent (ie when uart_circ is not empty), and inhibited when there is no more data to send (ie when uart_circ is empty). Signed-off-by: Erwan Le Ray Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/stm32-usart.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 2e75b586e5bf..2085f10aabfa 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -300,27 +300,26 @@ static void stm32_transmit_chars_pio(struct uart_port *port) struct stm32_port *stm32_port = to_stm32_port(port); struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; struct circ_buf *xmit = &port->state->xmit; - unsigned int isr; - int ret; if (stm32_port->tx_dma_busy) { stm32_clr_bits(port, ofs->cr3, USART_CR3_DMAT); stm32_port->tx_dma_busy = false; } - ret = readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr, - isr, - (isr & USART_SR_TXE), - 10, 100000); - - if (ret) - dev_err(port->dev, "tx empty not set\n"); - - stm32_set_bits(port, ofs->cr1, USART_CR1_TXEIE); + while (!uart_circ_empty(xmit)) { + /* Check that TDR is empty before filling FIFO */ + if (!(readl_relaxed(port->membase + ofs->isr) & USART_SR_TXE)) + break; + writel_relaxed(xmit->buf[xmit->tail], port->membase + ofs->tdr); + xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); + port->icount.tx++; + } - writel_relaxed(xmit->buf[xmit->tail], port->membase + ofs->tdr); - xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); - port->icount.tx++; + /* rely on TXE irq (mask or unmask) for sending remaining data */ + if (uart_circ_empty(xmit)) + stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE); + else + stm32_set_bits(port, ofs->cr1, USART_CR1_TXEIE); } static void stm32_transmit_chars_dma(struct uart_port *port) -- cgit