Adds the support of TX FIFO threshold in order to improve the TX FIFO
management:
- TX FIFO threshold irq enabling (instead of relying on tx empty / fifo
not full irq that generates one irq/char)
- TXCFG is set to half fifo size (e.g. 16/2 = 8 data for a 16 data depth
FIFO)
- irq rate may be reduced by up to 1/TXCFG, e.g. 1 over 8 with current
TXCFG setting.
Signed-off-by: Erwan Le Ray <erwan.le...@st.com>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 8316e19..397d86d 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -298,6 +298,32 @@ static void stm32_tx_dma_complete(void *arg)
stm32_transmit_chars(port);
}
+static void stm32_tx_interrupt_enable(struct uart_port *port)
+{
+ struct stm32_port *stm32_port = to_stm32_port(port);
+ struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+
+ /*
+ * Enables TX FIFO threashold irq when FIFO is enabled,
+ * or TX empty irq when FIFO is disabled
+ */
+ if (stm32_port->fifoen)
+ stm32_set_bits(port, ofs->cr3, USART_CR3_TXFTIE);
+ else
+ stm32_set_bits(port, ofs->cr1, USART_CR1_TXEIE);
+}
+
+static void stm32_tx_interrupt_disable(struct uart_port *port)
+{
+ struct stm32_port *stm32_port = to_stm32_port(port);
+ struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+
+ if (stm32_port->fifoen)
+ stm32_clr_bits(port, ofs->cr3, USART_CR3_TXFTIE);
+ else
+ stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
+}
+
static void stm32_transmit_chars_pio(struct uart_port *port)
{
struct stm32_port *stm32_port = to_stm32_port(port);
@@ -320,9 +346,9 @@ static void stm32_transmit_chars_pio(struct uart_port *port)
/* 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);
+ stm32_tx_interrupt_disable(port);
else
- stm32_set_bits(port, ofs->cr1, USART_CR1_TXEIE);
+ stm32_tx_interrupt_enable(port);
}
static void stm32_transmit_chars_dma(struct uart_port *port)
@@ -404,7 +430,7 @@ static void stm32_transmit_chars(struct uart_port *port)
}
if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
- stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
+ stm32_tx_interrupt_disable(port);
return;
}
@@ -422,7 +448,7 @@ static void stm32_transmit_chars(struct uart_port *port)
uart_write_wakeup(port);
if (uart_circ_empty(xmit))
- stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
+ stm32_tx_interrupt_disable(port);
}
static irqreturn_t stm32_interrupt(int irq, void *ptr)
@@ -501,10 +527,7 @@ static unsigned int stm32_get_mctrl(struct uart_port *port)
/* Transmit stop */
static void stm32_stop_tx(struct uart_port *port)
{
- struct stm32_port *stm32_port = to_stm32_port(port);
- struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
-
- stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
+ stm32_tx_interrupt_disable(port);
}
/* There are probably characters waiting to be transmitted. */
@@ -575,6 +598,13 @@ static int stm32_startup(struct uart_port *port)
val |= USART_CR1_FIFOEN;
stm32_set_bits(port, ofs->cr1, val);
+ if (stm32_port->fifoen) {
+ val = readl_relaxed(port->membase + ofs->cr3);
+ val &= ~USART_CR3_TXFTCFG_MASK;
+ val |= USART_CR3_TXFTCFG_HALF << USART_CR3_TXFTCFG_SHIFT;
+ writel_relaxed(val, port->membase + ofs->cr3);
+ }
+
return 0;
}
@@ -662,7 +692,9 @@ static void stm32_set_termios(struct uart_port *port,
struct ktermios *termios,
if (stm32_port->fifoen)
cr1 |= USART_CR1_FIFOEN;
cr2 = 0;
- cr3 = 0;
+ cr3 = readl_relaxed(port->membase + ofs->cr3);
+ cr3 &= USART_CR3_TXFTIE | USART_CR3_RXFTCFG | USART_CR3_RXFTIE
+ | USART_CR3_TXFTCFG_MASK;
if (cflag & CSTOPB)
cr2 |= USART_CR2_STOP_2B;
@@ -869,6 +901,7 @@ static int stm32_init_port(struct stm32_port *stm32port,
port->flags = UPF_BOOT_AUTOCONF;
port->ops = &stm32_uart_ops;
port->dev = &pdev->dev;
+ port->fifosize = stm32port->info->cfg.fifosize;
ret = platform_get_irq(pdev, 0);
if (ret <= 0) {
diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index fcd01fe..a598446 100644
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -27,6 +27,7 @@ struct stm32_usart_config {
bool has_7bits_data;
bool has_wakeup;
bool has_fifo;
+ int fifosize;
};
struct stm32_usart_info {
@@ -54,6 +55,7 @@ struct stm32_usart_info stm32f4_info = {
.cfg = {
.uart_enable_bit = 13,
.has_7bits_data = false,
+ .fifosize = 1,
}
};
@@ -74,6 +76,7 @@ struct stm32_usart_info stm32f7_info = {
.cfg = {
.uart_enable_bit = 0,
.has_7bits_data = true,
+ .fifosize = 1,
}
};
@@ -96,6 +99,7 @@ struct stm32_usart_info stm32h7_info = {
.has_7bits_data = true,
.has_wakeup = true,
.has_fifo = true,
+ .fifosize = 16,
}
};
@@ -204,6 +208,15 @@ struct stm32_usart_info stm32h7_info = {
#define USART_CR3_WUS_MASK GENMASK(21, 20) /* H7 */
#define USART_CR3_WUS_START_BIT BIT(21) /* H7 */
#define USART_CR3_WUFIE BIT(22) /* H7 */
+#define USART_CR3_TXFTIE BIT(23) /* H7 */
+#define USART_CR3_TCBGTIE BIT(24) /* H7 */
+#define USART_CR3_RXFTCFG GENMASK(27, 25) /* H7 */
+#define USART_CR3_RXFTIE BIT(28) /* H7 */
+#define USART_CR3_TXFTCFG_MASK GENMASK(31, 29) /* H7 */
+#define USART_CR3_TXFTCFG_SHIFT 29 /* H7 */
+
+/* TX FIFO threashold set to half of its depth */
+#define USART_CR3_TXFTCFG_HALF 0x2
/* USART_GTPR */
#define USART_GTPR_PSC_MASK GENMASK(7, 0)
--
1.9.1
