From: Radu Pirea radu-nicolae.pirea@nxp.com
Replace DMA single transactions with DMA cyclic transactions. Characters may be lost between two single DMA transactions if the CPU is running at lower frequencies.
Signed-off-by: Radu Pirea radu-nicolae.pirea@nxp.com Co-developed-by: Larisa Grigore larisa.grigore@oss.nxp.com Signed-off-by: Larisa Grigore larisa.grigore@oss.nxp.com --- drivers/tty/serial/fsl_linflexuart.c | 119 +++++++++++++++------------ 1 file changed, 68 insertions(+), 51 deletions(-)
diff --git a/drivers/tty/serial/fsl_linflexuart.c b/drivers/tty/serial/fsl_linflexuart.c index dff37c68cff0..4598c7ff669e 100644 --- a/drivers/tty/serial/fsl_linflexuart.c +++ b/drivers/tty/serial/fsl_linflexuart.c @@ -6,6 +6,7 @@ * Copyright 2017-2019, 2021-2022, 2025 NXP */
+#include <linux/circ_buf.h> #include <linux/clk.h> #include <linux/console.h> #include <linux/dma-mapping.h> @@ -180,7 +181,7 @@ struct linflex_port { dma_addr_t dma_rx_buf_bus; dma_cookie_t dma_tx_cookie; dma_cookie_t dma_rx_cookie; - unsigned char *dma_rx_buf_virt; + struct circ_buf dma_rx_ring_buf; unsigned int dma_tx_bytes; int dma_tx_in_progress; int dma_rx_in_progress; @@ -210,28 +211,63 @@ to_linflex_port(struct uart_port *uart) return container_of(uart, struct linflex_port, port); }
-static void linflex_copy_rx_to_tty(struct linflex_port *lfport, - struct tty_port *tty, int count) +static void linflex_copy_rx_to_tty(struct linflex_port *lfport) { - size_t copied; - - lfport->port.icount.rx += count; + struct circ_buf *ring_buf = &lfport->dma_rx_ring_buf; + struct tty_port *port = &lfport->port.state->port; + size_t count, received = 0, copied = 0; + struct dma_tx_state state; + enum dma_status dmastat; + int new_head;
- if (!tty) { + if (!port) { dev_err(lfport->port.dev, "No tty port\n"); return; }
+ dmastat = dmaengine_tx_status(lfport->dma_rx_chan, lfport->dma_rx_cookie, &state); + if (dmastat == DMA_ERROR) { + dev_err(lfport->port.dev, "Rx DMA transfer failed!\n"); + return; + } + + new_head = FSL_UART_RX_DMA_BUFFER_SIZE - state.residue; + if (ring_buf->head == new_head) + return; + + ring_buf->head = new_head; dma_sync_single_for_cpu(lfport->port.dev, lfport->dma_rx_buf_bus, FSL_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE); - copied = tty_insert_flip_string(tty, - ((unsigned char *)(lfport->dma_rx_buf_virt)), - count);
- if (copied != count) { - WARN_ON(1); - dev_err(lfport->port.dev, "RxData copy to tty layer failed\n"); + if (ring_buf->head > FSL_UART_RX_DMA_BUFFER_SIZE) + dev_err_once(lfport->port.dev, + "Circular buffer head bigger than the buffer size\n"); + + if (ring_buf->head < ring_buf->tail) { + count = FSL_UART_RX_DMA_BUFFER_SIZE - ring_buf->tail; + received += count; + copied += tty_insert_flip_string(port, ring_buf->buf + ring_buf->tail, count); + ring_buf->tail = 0; + lfport->port.icount.rx += count; } + + if (ring_buf->head > ring_buf->tail) { + count = ring_buf->head - ring_buf->tail; + received += count; + copied += tty_insert_flip_string(port, ring_buf->buf + ring_buf->tail, count); + if (ring_buf->head >= FSL_UART_RX_DMA_BUFFER_SIZE) + ring_buf->head = 0; + ring_buf->tail = ring_buf->head; + lfport->port.icount.rx += count; + } + + if (copied != received) + dev_err_once(lfport->port.dev, "RxData copy to tty layer failed\n"); + + dma_sync_single_for_device(lfport->port.dev, lfport->dma_rx_buf_bus, + FSL_UART_RX_DMA_BUFFER_SIZE, + DMA_FROM_DEVICE); + tty_flip_buffer_push(port); }
static void linflex_enable_dma_rx(struct uart_port *port) @@ -348,8 +384,6 @@ static void _linflex_stop_rx(struct uart_port *port) static void linflex_stop_rx(struct uart_port *port) { struct linflex_port *lfport = to_linflex_port(port); - struct dma_tx_state state; - unsigned int count;
_linflex_stop_rx(port);
@@ -357,14 +391,12 @@ static void linflex_stop_rx(struct uart_port *port) return;
dmaengine_pause(lfport->dma_rx_chan); - dmaengine_tx_status(lfport->dma_rx_chan, - lfport->dma_rx_cookie, &state); + linflex_copy_rx_to_tty(lfport); + lfport->dma_rx_ring_buf.head = 0; + lfport->dma_rx_ring_buf.tail = 0; dmaengine_terminate_all(lfport->dma_rx_chan); - count = FSL_UART_RX_DMA_BUFFER_SIZE - state.residue;
lfport->dma_rx_in_progress = 0; - linflex_copy_rx_to_tty(lfport, &port->state->port, count); - tty_flip_buffer_push(&port->state->port); }
static void linflex_put_char(struct uart_port *sport, unsigned char c) @@ -501,11 +533,12 @@ static int linflex_dma_rx(struct linflex_port *lfport) dma_sync_single_for_device(lfport->port.dev, lfport->dma_rx_buf_bus, FSL_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE); - lfport->dma_rx_desc = dmaengine_prep_slave_single(lfport->dma_rx_chan, - lfport->dma_rx_buf_bus, - FSL_UART_RX_DMA_BUFFER_SIZE, - DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT | - DMA_CTRL_ACK); + lfport->dma_rx_desc = + dmaengine_prep_dma_cyclic(lfport->dma_rx_chan, + lfport->dma_rx_buf_bus, + FSL_UART_RX_DMA_BUFFER_SIZE, + FSL_UART_RX_DMA_BUFFER_SIZE / 2, + DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT);
if (!lfport->dma_rx_desc) { dev_err(lfport->port.dev, "Not able to get desc for rx\n"); @@ -525,11 +558,8 @@ static int linflex_dma_rx(struct linflex_port *lfport) static void linflex_dma_rx_complete(void *arg) { struct linflex_port *lfport = arg; - struct tty_port *port = &lfport->port.state->port; unsigned long flags;
- timer_delete_sync(&lfport->timer); - uart_port_lock_irqsave(&lfport->port, &flags);
/* stopped before? */ @@ -538,34 +568,17 @@ static void linflex_dma_rx_complete(void *arg) return; }
- lfport->dma_rx_in_progress = 0; - linflex_copy_rx_to_tty(lfport, port, FSL_UART_RX_DMA_BUFFER_SIZE); - tty_flip_buffer_push(port); - linflex_dma_rx(lfport); + linflex_copy_rx_to_tty(lfport);
uart_port_unlock_irqrestore(&lfport->port, flags); - mod_timer(&lfport->timer, jiffies + lfport->dma_rx_timeout); }
static void linflex_timer_func(struct timer_list *t) { struct linflex_port *lfport = timer_container_of(lfport, t, timer); - unsigned long flags; - - uart_port_lock_irqsave(&lfport->port, &flags);
- /* stopped before? */ - if (!lfport->dma_rx_in_progress) { - uart_port_unlock_irqrestore(&lfport->port, flags); - return; - } - - linflex_stop_rx(&lfport->port); - linflex_dma_rx(lfport); - - uart_port_unlock_irqrestore(&lfport->port, flags); - mod_timer(&lfport->timer, jiffies + lfport->dma_rx_timeout); + linflex_dma_rx_complete(lfport); }
static void _linflex_start_tx(struct uart_port *port) @@ -827,8 +840,8 @@ static int linflex_dma_rx_request(struct uart_port *port) { struct linflex_port *lfport = to_linflex_port(port); struct dma_slave_config dma_rx_sconfig; - unsigned char *dma_buf; dma_addr_t dma_bus; + char *dma_buf; int ret;
dma_buf = devm_kmalloc(port->dev, FSL_UART_RX_DMA_BUFFER_SIZE, @@ -860,7 +873,9 @@ static int linflex_dma_rx_request(struct uart_port *port) return ret; }
- lfport->dma_rx_buf_virt = dma_buf; + lfport->dma_rx_ring_buf.buf = dma_buf; + lfport->dma_rx_ring_buf.head = 0; + lfport->dma_rx_ring_buf.tail = 0; lfport->dma_rx_buf_bus = dma_bus; lfport->dma_rx_in_progress = 0;
@@ -883,10 +898,12 @@ static void linflex_dma_rx_free(struct uart_port *port)
dma_unmap_single(lfport->port.dev, lfport->dma_rx_buf_bus, FSL_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE); - devm_kfree(lfport->port.dev, lfport->dma_rx_buf_virt); + devm_kfree(lfport->port.dev, lfport->dma_rx_ring_buf.buf);
lfport->dma_rx_buf_bus = 0; - lfport->dma_rx_buf_virt = NULL; + lfport->dma_rx_ring_buf.buf = NULL; + lfport->dma_rx_ring_buf.head = 0; + lfport->dma_rx_ring_buf.tail = 0; }
static int linflex_startup(struct uart_port *port)