This series reworks STM32 USART DMA TX state management, and fix flow control.
Valentin Caron (4):
serial: stm32: move tx dma terminate DMA to shutdown
serial: stm32: rework TX DMA state condition
serial: stm32: fix flow control transfer in DMA mode
serial: stm32: correct loop for dma error handling
drivers/tty/serial/stm32-usart.c | 74 ++++++++++++++++++++++++--------
drivers/tty/serial/stm32-usart.h | 2 +-
2 files changed, 56 insertions(+), 20 deletions(-)
--
2.17.1
Terminate DMA transaction and clear CR3_DMAT when shutdown is requested,
instead of when remove is requested. If DMA transfer is not stopped in
shutdown ops, driver will fail to start a new DMA transfer after next
startup ops.
Fixes: 3489187204eb ("serial: stm32: adding dma support")
Signed-off-by: Erwan Le Ray <[email protected]>
Signed-off-by: Valentin Caron <[email protected]>
---
drivers/tty/serial/stm32-usart.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 3244e7f6818c..6cfc3bec6749 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -883,6 +883,11 @@ 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);
+ stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT);
+ }
+
/* Disable modem control interrupts */
stm32_usart_disable_ms(port);
@@ -1570,7 +1575,6 @@ static int stm32_usart_serial_remove(struct platform_device *pdev)
writel_relaxed(cr3, port->membase + ofs->cr3);
if (stm32_port->tx_ch) {
- dmaengine_terminate_async(stm32_port->tx_ch);
stm32_usart_of_dma_tx_remove(stm32_port, pdev);
dma_release_channel(stm32_port->tx_ch);
}
--
2.17.1
In this error handling, "transmit_chars_dma" function will call
"transmit_chars_pio" once per characters. But "transmit_chars_pio" will
continue to send characters while xmit buffer is not empty.
Remove this useless loop, one call is sufficient.
Signed-off-by: Valentin Caron <[email protected]>
---
drivers/tty/serial/stm32-usart.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 788e002688f2..1f89ab0e49ac 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -477,7 +477,7 @@ static void stm32_usart_transmit_chars_dma(struct uart_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, i;
+ unsigned int count;
if (stm32_usart_tx_dma_started(stm32port)) {
if (!stm32_usart_tx_dma_enabled(stm32port))
@@ -542,8 +542,7 @@ static void stm32_usart_transmit_chars_dma(struct uart_port *port)
return;
fallback_err:
- for (i = count; i > 0; i--)
- stm32_usart_transmit_chars_pio(port);
+ stm32_usart_transmit_chars_pio(port);
}
static void stm32_usart_transmit_chars(struct uart_port *port)
--
2.17.1
If flow control is enabled, framework will call stop_tx to
pause transfer and then call start_tx to resume transfer.
Clear USART_CR3_DMAT bit in stop_tx ops to pause DMA transfer.
Signed-off-by: Erwan Le Ray <[email protected]>
Signed-off-by: Valentin Caron <[email protected]>
---
drivers/tty/serial/stm32-usart.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 52755a576bc2..788e002688f2 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -707,8 +707,11 @@ static void stm32_usart_stop_tx(struct uart_port *port)
{
struct stm32_port *stm32_port = to_stm32_port(port);
struct serial_rs485 *rs485conf = &port->rs485;
+ const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
stm32_usart_tx_interrupt_disable(port);
+ 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);
if (rs485conf->flags & SER_RS485_ENABLED) {
if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
--
2.17.1
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 <[email protected]>
Signed-off-by: Valentin Caron <[email protected]>
---
drivers/tty/serial/stm32-usart.c | 66 +++++++++++++++++++++++---------
drivers/tty/serial/stm32-usart.h | 2 +-
2 files changed, 49 insertions(+), 19 deletions(-)
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 */
--
2.17.1