Add early console support in stm32 uart driver.
Signed-off-by: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>
Signed-off-by: Valentin Caron <valentin.caron@xxxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 6 +++
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/stm32-usart.c | 51 +++++++++++++++++++
3 files changed, 58 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3f1cc5e317ed..e941c3351c7a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1264,6 +1264,12 @@
address must be provided, and the serial port must
already be setup and configured.
+ stm32,<addr>
+ Use early console provided by ST Microelectronics
+ serial driver for STM32 SoCs. A valid base address
+ must be provided, and the serial port must already
+ be setup and configured.
+
earlyprintk= [X86,SH,ARM,M68k,S390]
earlyprintk=vga
earlyprintk=sclp
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 6949e883ffab..ed59de8d2e11 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1443,6 +1443,7 @@ config SERIAL_STM32_CONSOLE
bool "Support for console on STM32"
depends on SERIAL_STM32=y
select SERIAL_CORE_CONSOLE
+ select SERIAL_EARLYCON
config SERIAL_MVEBU_UART
bool "Marvell EBU serial port support"
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index d2cf789c7997..b6852a5a9143 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1767,6 +1767,57 @@ static struct console stm32_console = {
#define STM32_SERIAL_CONSOLE NULL
#endif /* CONFIG_SERIAL_STM32_CONSOLE */
+#ifdef CONFIG_SERIAL_EARLYCON
+static void early_stm32_usart_console_putchar(struct uart_port *port, unsigned char ch)
+{
+ struct stm32_usart_info *info = port->private_data;
+
+ while (!(readl_relaxed(port->membase + info->ofs.isr) & USART_SR_TXE))
+ cpu_relax();
+
+ writel_relaxed(ch, port->membase + info->ofs.tdr);
+}
+
+static void early_stm32_serial_write(struct console *console, const char *s, unsigned int count)
+{
+ struct earlycon_device *device = console->data;
+ struct uart_port *port = &device->port;
+
+ uart_console_write(port, s, count, early_stm32_usart_console_putchar);
+}
+
+static int __init early_stm32_h7_serial_setup(struct earlycon_device *device, const char *options)
+{
+ if (!(device->port.membase || device->port.iobase))
+ return -ENODEV;
+ device->port.private_data = &stm32h7_info;
+ device->con->write = early_stm32_serial_write;
+ return 0;
+}
+
+static int __init early_stm32_f7_serial_setup(struct earlycon_device *device, const char *options)
+{
+ if (!(device->port.membase || device->port.iobase))
+ return -ENODEV;
+ device->port.private_data = &stm32f7_info;
+ device->con->write = early_stm32_serial_write;
+ return 0;
+}
+
+static int __init early_stm32_f4_serial_setup(struct earlycon_device *device, const char *options)
+{
+ if (!(device->port.membase || device->port.iobase))
+ return -ENODEV;
+ device->port.private_data = &stm32f4_info;
+ device->con->write = early_stm32_serial_write;
+ return 0;
+}
+
+OF_EARLYCON_DECLARE(stm32, "st,stm32h7-uart", early_stm32_h7_serial_setup);
+OF_EARLYCON_DECLARE(stm32, "st,stm32f7-uart", early_stm32_f7_serial_setup);
+OF_EARLYCON_DECLARE(stm32, "st,stm32-uart", early_stm32_f4_serial_setup);
+#endif /* CONFIG_SERIAL_EARLYCON */
+
static struct uart_driver stm32_usart_driver = {
.driver_name = DRIVER_NAME,
.dev_name = STM32_SERIAL_NAME,
--
2.25.1
