From 9a135f16d228857c5c1212a58050196883343d1e Mon Sep 17 00:00:00 2001 From: Valentin Caron Date: Tue, 4 Jan 2022 19:24:43 +0100 Subject: serial: stm32: rework TX DMA state condition TX DMA state condition is handled by tx_dma_busy boolean. This boolean is set when dma descriptor is requested and reset when dma channel is stopped (dma_terminate). In stm32_usart_serial_remove(), stm32_usart_stop_tx() and stm32_usart_transmit_chars_dma() fallback error case, DMA channel is stopped but tx_dma_busy is not handled. Rework the driver by using two new functions to solve this issue: - stm32_usart_tx_dma_started return true if DMA TX have a descriptor. - stm32_usart_tx_dma_enabled return true if DMAT bit is set. stm32_usart_tx_dma_started uses tx_dma_busy flag to prevent dual DMA transaction at the same time. This flag is set when a DMA transaction begins and is unset when dmaengine_terminate_async function is called. A new DMA transaction cannot be created if this flag is set. Create a new function "stm32_usart_tx_dma_terminate" to be sure the flag is unset after each call of dmaengine_terminate_async. Signed-off-by: Erwan Le Ray Signed-off-by: Valentin Caron Link: https://lore.kernel.org/r/20220104182445.4195-3-valentin.caron@foss.st.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/stm32-usart.c | 66 +++++++++++++++++++++++++++++----------- drivers/tty/serial/stm32-usart.h | 2 +- 2 files changed, 49 insertions(+), 19 deletions(-) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 6cfc3bec6749..52755a576bc2 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -365,6 +365,31 @@ static unsigned int stm32_usart_receive_chars(struct uart_port *port, bool force return size; } +static void stm32_usart_tx_dma_terminate(struct stm32_port *stm32_port) +{ + dmaengine_terminate_async(stm32_port->tx_ch); + stm32_port->tx_dma_busy = false; +} + +static bool stm32_usart_tx_dma_started(struct stm32_port *stm32_port) +{ + /* + * We cannot use the function "dmaengine_tx_status" to know the + * status of DMA. This function does not show if the "dma complete" + * callback of the DMA transaction has been called. So we prefer + * to use "tx_dma_busy" flag to prevent dual DMA transaction at the + * same time. + */ + return stm32_port->tx_dma_busy; +} + +static bool stm32_usart_tx_dma_enabled(struct stm32_port *stm32_port) +{ + const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; + + return !!(readl_relaxed(stm32_port->port.membase + ofs->cr3) & USART_CR3_DMAT); +} + static void stm32_usart_tx_dma_complete(void *arg) { struct uart_port *port = arg; @@ -372,9 +397,8 @@ static void stm32_usart_tx_dma_complete(void *arg) const struct stm32_usart_offsets *ofs = &stm32port->info->ofs; unsigned long flags; - dmaengine_terminate_async(stm32port->tx_ch); stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); - stm32port->tx_dma_busy = false; + stm32_usart_tx_dma_terminate(stm32port); /* Let's see if we have pending data to send */ spin_lock_irqsave(&port->lock, flags); @@ -428,10 +452,8 @@ static void stm32_usart_transmit_chars_pio(struct uart_port *port) const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; struct circ_buf *xmit = &port->state->xmit; - if (stm32_port->tx_dma_busy) { + if (stm32_usart_tx_dma_enabled(stm32_port)) stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); - stm32_port->tx_dma_busy = false; - } while (!uart_circ_empty(xmit)) { /* Check that TDR is empty before filling FIFO */ @@ -457,10 +479,11 @@ static void stm32_usart_transmit_chars_dma(struct uart_port *port) struct dma_async_tx_descriptor *desc = NULL; unsigned int count, i; - if (stm32port->tx_dma_busy) + if (stm32_usart_tx_dma_started(stm32port)) { + if (!stm32_usart_tx_dma_enabled(stm32port)) + stm32_usart_set_bits(port, ofs->cr3, USART_CR3_DMAT); return; - - stm32port->tx_dma_busy = true; + } count = uart_circ_chars_pending(xmit); @@ -491,13 +514,21 @@ static void stm32_usart_transmit_chars_dma(struct uart_port *port) if (!desc) goto fallback_err; + /* + * Set "tx_dma_busy" flag. This flag will be released when + * dmaengine_terminate_async will be called. This flag helps + * transmit_chars_dma not to start another DMA transaction + * if the callback of the previous is not yet called. + */ + stm32port->tx_dma_busy = true; + desc->callback = stm32_usart_tx_dma_complete; desc->callback_param = port; /* Push current DMA TX transaction in the pending queue */ if (dma_submit_error(dmaengine_submit(desc))) { /* dma no yet started, safe to free resources */ - dmaengine_terminate_async(stm32port->tx_ch); + stm32_usart_tx_dma_terminate(stm32port); goto fallback_err; } @@ -522,12 +553,13 @@ static void stm32_usart_transmit_chars(struct uart_port *port) struct circ_buf *xmit = &port->state->xmit; if (port->x_char) { - if (stm32_port->tx_dma_busy) + if (stm32_usart_tx_dma_started(stm32_port) && + stm32_usart_tx_dma_enabled(stm32_port)) stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); writel_relaxed(port->x_char, port->membase + ofs->tdr); port->x_char = 0; port->icount.tx++; - if (stm32_port->tx_dma_busy) + if (stm32_usart_tx_dma_started(stm32_port)) stm32_usart_set_bits(port, ofs->cr3, USART_CR3_DMAT); return; } @@ -719,9 +751,8 @@ static void stm32_usart_flush_buffer(struct uart_port *port) const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; if (stm32_port->tx_ch) { - dmaengine_terminate_async(stm32_port->tx_ch); + stm32_usart_tx_dma_terminate(stm32_port); stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); - stm32_port->tx_dma_busy = false; } } @@ -883,10 +914,11 @@ static void stm32_usart_shutdown(struct uart_port *port) u32 val, isr; int ret; - if (stm32_port->tx_dma_busy) { - dmaengine_terminate_async(stm32_port->tx_ch); + if (stm32_usart_tx_dma_enabled(stm32_port)) stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT); - } + + if (stm32_usart_tx_dma_started(stm32_port)) + stm32_usart_tx_dma_terminate(stm32_port); /* Disable modem control interrupts */ stm32_usart_disable_ms(port); @@ -1424,8 +1456,6 @@ static int stm32_usart_of_dma_tx_probe(struct stm32_port *stm32port, struct dma_slave_config config; int ret; - stm32port->tx_dma_busy = false; - stm32port->tx_buf = dma_alloc_coherent(dev, TX_BUF_L, &stm32port->tx_dma_buf, GFP_KERNEL); diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h index e23916bfbb60..feab952aec16 100644 --- a/drivers/tty/serial/stm32-usart.h +++ b/drivers/tty/serial/stm32-usart.h @@ -264,7 +264,7 @@ struct stm32_port { u32 cr1_irq; /* USART_CR1_RXNEIE or RTOIE */ u32 cr3_irq; /* USART_CR3_RXFTIE */ int last_res; - bool tx_dma_busy; /* dma tx busy */ + bool tx_dma_busy; /* dma tx transaction in progress */ bool throttled; /* port throttled */ bool hw_flow_control; bool swap; /* swap RX & TX pins */ -- cgit