serial: stm32: remove infinite loop possibility in putchar function

Rework stm32_usart_console_putchar() function in order to anticipate
the case where the character can never be sent.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20220419085330.1178925-2-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index f886976daef6dc62bb2bce26402d9fce1b9255e8..9910a18779af5bfd2d23d9add77e18bf9916f691 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1640,10 +1640,16 @@ static void stm32_usart_console_putchar(struct uart_port *port, unsigned char ch
 {
        struct stm32_port *stm32_port = to_stm32_port(port);
        const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+       u32 isr;
+       int ret;
 
-       while (!(readl_relaxed(port->membase + ofs->isr) & USART_SR_TXE))
-               cpu_relax();
-
+       ret = readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr, isr,
+                                               (isr & USART_SR_TXE), 100,
+                                               STM32_USART_TIMEOUT_USEC);
+       if (ret != 0) {
+               dev_err(port->dev, "Error while sending data in UART TX : %d\n", ret);
+               return;
+       }
        writel_relaxed(ch, port->membase + ofs->tdr);
 }
 

diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index feab952aec16779314d24cdda829f3064f18acef..d734c4a5fd24c208a9904591a94488ce8461102b 100644 (file)
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -251,6 +251,8 @@ struct stm32_usart_info stm32h7_info = {
 #define RX_BUF_P (RX_BUF_L / 2)         /* dma rx buffer period     */
 #define TX_BUF_L RX_BUF_L       /* dma tx buffer length     */
 
+#define STM32_USART_TIMEOUT_USEC USEC_PER_SEC /* 1s timeout in µs */
+
 struct stm32_port {
        struct uart_port port;
        struct clk *clk;