From 1788cf6a91d9fa9aa61fc2917afe192c23d67f6a Mon Sep 17 00:00:00 2001 From: "Jiri Slaby (SUSE)" Date: Fri, 5 Apr 2024 08:08:23 +0200 Subject: tty: serial: switch from circ_buf to kfifo MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Switch from struct circ_buf to proper kfifo. kfifo provides much better API, esp. when wrap-around of the buffer needs to be taken into account. Look at pl011_dma_tx_refill() or cpm_uart_tx_pump() changes for example. Kfifo API can also fill in scatter-gather DMA structures, so it easier for that use case too. Look at lpuart_dma_tx() for example. Note that not all drivers can be converted to that (like atmel_serial), they handle DMA specially. Note that usb-serial uses kfifo for TX for ages. omap needed a bit more care as it needs to put a char into FIFO to start the DMA transfer when OMAP_DMA_TX_KICK is set. In that case, we have to do kfifo_dma_out_prepare twice: once to find out the tx_size (to find out if it is worths to do DMA at all -- size >= 4), the second time for the actual transfer. All traces of circ_buf are removed from serial_core.h (and its struct uart_state). Signed-off-by: Jiri Slaby (SUSE) Cc: Al Cooper Cc: Matthias Brugger Cc: AngeloGioacchino Del Regno Cc: Kumaravel Thiagarajan Cc: Tharun Kumar P Cc: Russell King Cc: Vineet Gupta Cc: Richard Genoud Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Claudiu Beznea Cc: Alexander Shiyan Cc: Baruch Siach Cc: Maciej W. Rozycki Cc: Shawn Guo Cc: Sascha Hauer Cc: Fabio Estevam Cc: Neil Armstrong Cc: Kevin Hilman Cc: Jerome Brunet Cc: Martin Blumenstingl Cc: Taichi Sugaya Cc: Takao Orito Cc: Bjorn Andersson Cc: Konrad Dybcio Cc: Pali Rohár Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Aneesh Kumar K.V Cc: Naveen N. Rao Cc: Manivannan Sadhasivam Cc: Krzysztof Kozlowski Cc: Alim Akhtar Cc: Laxman Dewangan Cc: Thierry Reding Cc: Jonathan Hunter Cc: Orson Zhai Cc: Baolin Wang Cc: Chunyan Zhang Cc: Patrice Chotard Cc: Maxime Coquelin Cc: Alexandre Torgue Cc: David S. Miller Cc: Hammer Hsieh Cc: Peter Korsgaard Cc: Timur Tabi Cc: Michal Simek Cc: Sumit Semwal Cc: Christian König Link: https://lore.kernel.org/r/20240405060826.2521-13-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 54 +++++++++++++++++++++--------------------------- 1 file changed, 23 insertions(+), 31 deletions(-) (limited to 'drivers/tty/serial/imx.c') diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index e14813250616..56b76a221082 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -8,6 +8,7 @@ * Copyright (C) 2004 Pengutronix */ +#include #include #include #include @@ -521,7 +522,8 @@ static void imx_uart_dma_tx(struct imx_port *sport); /* called with port.lock taken and irqs off */ static inline void imx_uart_transmit_buffer(struct imx_port *sport) { - struct circ_buf *xmit = &sport->port.state->xmit; + struct tty_port *tport = &sport->port.state->port; + unsigned char c; if (sport->port.x_char) { /* Send next char */ @@ -531,7 +533,8 @@ static inline void imx_uart_transmit_buffer(struct imx_port *sport) return; } - if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) { + if (kfifo_is_empty(&tport->xmit_fifo) || + uart_tx_stopped(&sport->port)) { imx_uart_stop_tx(&sport->port); return; } @@ -555,26 +558,22 @@ static inline void imx_uart_transmit_buffer(struct imx_port *sport) return; } - while (!uart_circ_empty(xmit) && - !(imx_uart_readl(sport, imx_uart_uts_reg(sport)) & UTS_TXFULL)) { - /* send xmit->buf[xmit->tail] - * out the port here */ - imx_uart_writel(sport, xmit->buf[xmit->tail], URTX0); - uart_xmit_advance(&sport->port, 1); - } + while (!(imx_uart_readl(sport, imx_uart_uts_reg(sport)) & UTS_TXFULL) && + uart_fifo_get(&sport->port, &c)) + imx_uart_writel(sport, c, URTX0); - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) + if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS) uart_write_wakeup(&sport->port); - if (uart_circ_empty(xmit)) + if (kfifo_is_empty(&tport->xmit_fifo)) imx_uart_stop_tx(&sport->port); } static void imx_uart_dma_tx_callback(void *data) { struct imx_port *sport = data; + struct tty_port *tport = &sport->port.state->port; struct scatterlist *sgl = &sport->tx_sgl[0]; - struct circ_buf *xmit = &sport->port.state->xmit; unsigned long flags; u32 ucr1; @@ -592,10 +591,11 @@ static void imx_uart_dma_tx_callback(void *data) sport->dma_is_txing = 0; - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) + if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS) uart_write_wakeup(&sport->port); - if (!uart_circ_empty(xmit) && !uart_tx_stopped(&sport->port)) + if (!kfifo_is_empty(&tport->xmit_fifo) && + !uart_tx_stopped(&sport->port)) imx_uart_dma_tx(sport); else if (sport->port.rs485.flags & SER_RS485_ENABLED) { u32 ucr4 = imx_uart_readl(sport, UCR4); @@ -609,7 +609,7 @@ static void imx_uart_dma_tx_callback(void *data) /* called with port.lock taken and irqs off */ static void imx_uart_dma_tx(struct imx_port *sport) { - struct circ_buf *xmit = &sport->port.state->xmit; + struct tty_port *tport = &sport->port.state->port; struct scatterlist *sgl = sport->tx_sgl; struct dma_async_tx_descriptor *desc; struct dma_chan *chan = sport->dma_chan_tx; @@ -624,18 +624,10 @@ static void imx_uart_dma_tx(struct imx_port *sport) ucr4 &= ~UCR4_TCEN; imx_uart_writel(sport, ucr4, UCR4); - sport->tx_bytes = uart_circ_chars_pending(xmit); - - if (xmit->tail < xmit->head || xmit->head == 0) { - sport->dma_tx_nents = 1; - sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes); - } else { - sport->dma_tx_nents = 2; - sg_init_table(sgl, 2); - sg_set_buf(sgl, xmit->buf + xmit->tail, - UART_XMIT_SIZE - xmit->tail); - sg_set_buf(sgl + 1, xmit->buf, xmit->head); - } + sg_init_table(sgl, ARRAY_SIZE(sport->tx_sgl)); + sport->tx_bytes = kfifo_len(&tport->xmit_fifo); + sport->dma_tx_nents = kfifo_dma_out_prepare(&tport->xmit_fifo, sgl, + ARRAY_SIZE(sport->tx_sgl), sport->tx_bytes); ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE); if (ret == 0) { @@ -653,8 +645,7 @@ static void imx_uart_dma_tx(struct imx_port *sport) desc->callback = imx_uart_dma_tx_callback; desc->callback_param = sport; - dev_dbg(dev, "TX: prepare to send %lu bytes by DMA.\n", - uart_circ_chars_pending(xmit)); + dev_dbg(dev, "TX: prepare to send %u bytes by DMA.\n", sport->tx_bytes); ucr1 = imx_uart_readl(sport, UCR1); ucr1 |= UCR1_TXDMAEN; @@ -671,9 +662,10 @@ static void imx_uart_dma_tx(struct imx_port *sport) static void imx_uart_start_tx(struct uart_port *port) { struct imx_port *sport = (struct imx_port *)port; + struct tty_port *tport = &sport->port.state->port; u32 ucr1; - if (!sport->port.x_char && uart_circ_empty(&port->state->xmit)) + if (!sport->port.x_char && kfifo_is_empty(&tport->xmit_fifo)) return; /* @@ -749,7 +741,7 @@ static void imx_uart_start_tx(struct uart_port *port) return; } - if (!uart_circ_empty(&port->state->xmit) && + if (!kfifo_is_empty(&tport->xmit_fifo) && !uart_tx_stopped(port)) imx_uart_dma_tx(sport); return; -- cgit v1.2.3-59-g8ed1b From e533e4c62e9993e62e947ae9bbec34e4c7ae81c2 Mon Sep 17 00:00:00 2001 From: Esben Haabendal Date: Thu, 11 Apr 2024 14:19:23 +0200 Subject: serial: imx: Introduce timeout when waiting on transmitter empty By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential deadlock. In case of the timeout, there is not much we can do, so we simply ignore the transmitter state and optimistically try to continue. Signed-off-by: Esben Haabendal Acked-by: Marc Kleine-Budde Link: https://lore.kernel.org/r/919647898c337a46604edcabaf13d42d80c0915d.1712837613.git.esben@geanix.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'drivers/tty/serial/imx.c') diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 56b76a221082..79f1503cd75b 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include @@ -2002,7 +2003,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) struct imx_port *sport = imx_uart_ports[co->index]; struct imx_port_ucrs old_ucr; unsigned long flags; - unsigned int ucr1; + unsigned int ucr1, usr2; int locked = 1; if (sport->port.sysrq) @@ -2033,8 +2034,8 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) * Finally, wait for transmitter to become empty * and restore UCR1/2/3 */ - while (!(imx_uart_readl(sport, USR2) & USR2_TXDC)); - + read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC, + 0, USEC_PER_SEC, false, sport, USR2); imx_uart_ucrs_restore(sport, &old_ucr); if (locked) -- cgit v1.2.3-59-g8ed1b From a3d8728ab079951741efa11360df43dbfacba7ab Mon Sep 17 00:00:00 2001 From: Matthias Schiffer Date: Wed, 8 May 2024 15:37:44 +0200 Subject: serial: imx: Raise TX trigger level to 8 At the default TX trigger level of 2 in non-DMA mode (meaning that an interrupt is generated when less than 2 characters are left in the FIFO), we have observed frequent buffer underruns at 115200 Baud on an i.MX8M Nano. This can cause communication issues if the receiving side expects a continuous transfer. Increasing the level to 8 makes the UART trigger an interrupt earlier, giving the kernel enough time to refill the FIFO, at the cost of triggering one interrupt per ~24 instead of ~30 bytes of transmitted data (as the i.MX UART has a 32 byte FIFO). Signed-off-by: Michael Krummsdorf Signed-off-by: Matthias Schiffer Link: https://lore.kernel.org/r/20240508133744.35858-1-matthias.schiffer@ew.tq-group.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/tty/serial/imx.c') diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 79f1503cd75b..2eb22594960f 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1305,7 +1305,7 @@ static void imx_uart_clear_rx_errors(struct imx_port *sport) } -#define TXTL_DEFAULT 2 /* reset default */ +#define TXTL_DEFAULT 8 #define RXTL_DEFAULT 8 /* 8 characters or aging timer */ #define TXTL_DMA 8 /* DMA burst setting */ #define RXTL_DMA 9 /* DMA burst setting */ -- cgit v1.2.3-59-g8ed1b