From: Patrick Delaunay <patrick.delau...@st.com>

Add support for early debug printf, before the availability of
driver model and device tree support.

Signed-off-by: Patrick Delaunay <patrick.delau...@st.com>
Signed-off-by: Patrice Chotard <patrice.chot...@st.com>
---

 drivers/serial/Kconfig        |   9 ++++
 drivers/serial/serial_stm32.c | 105 +++++++++++++++++++++++++++++++++---------
 2 files changed, 92 insertions(+), 22 deletions(-)

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 5937910e5bf9..25ac869b0e64 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -315,6 +315,15 @@ config DEBUG_UART_MXC
          will need to provide parameters to make this work. The driver will
          be available until the real driver model serial is running.
 
+config DEBUG_UART_STM32
+       bool "STMicroelectronics STM32"
+       depends on STM32_SERIAL
+       help
+         Select this to enable a debug UART using the serial_stm32 driver
+         You will need to provide parameters to make this work.
+         The driver will be available until the real driver model
+         serial is running.
+
 config DEBUG_UART_UNIPHIER
        bool "UniPhier on-chip UART"
        depends on ARCH_UNIPHIER
diff --git a/drivers/serial/serial_stm32.c b/drivers/serial/serial_stm32.c
index 6717ffaaa5b9..724d6f967246 100644
--- a/drivers/serial/serial_stm32.c
+++ b/drivers/serial/serial_stm32.c
@@ -7,19 +7,21 @@
 #include <common.h>
 #include <clk.h>
 #include <dm.h>
-#include <asm/io.h>
 #include <serial.h>
+#include <watchdog.h>
+#include <asm/io.h>
 #include <asm/arch/stm32.h>
 #include "serial_stm32.h"
 
-static int stm32_serial_setbrg(struct udevice *dev, int baudrate)
+static void _stm32_serial_setbrg(fdt_addr_t base,
+                                struct stm32_uart_info *uart_info,
+                                u32 clock_rate,
+                                int baudrate)
 {
-       struct stm32x7_serial_platdata *plat = dev_get_platdata(dev);
-       bool stm32f4 = plat->uart_info->stm32f4;
-       fdt_addr_t base = plat->base;
+       bool stm32f4 = uart_info->stm32f4;
        u32 int_div, mantissa, fraction, oversampling;
 
-       int_div = DIV_ROUND_CLOSEST(plat->clock_rate, baudrate);
+       int_div = DIV_ROUND_CLOSEST(clock_rate, baudrate);
 
        if (int_div < 16) {
                oversampling = 8;
@@ -33,6 +35,14 @@ static int stm32_serial_setbrg(struct udevice *dev, int 
baudrate)
        fraction = int_div % oversampling;
 
        writel(mantissa | fraction, base + BRR_OFFSET(stm32f4));
+}
+
+static int stm32_serial_setbrg(struct udevice *dev, int baudrate)
+{
+       struct stm32x7_serial_platdata *plat = dev_get_platdata(dev);
+
+       _stm32_serial_setbrg(plat->base, plat->uart_info,
+                            plat->clock_rate, baudrate);
 
        return 0;
 }
@@ -58,11 +68,11 @@ static int stm32_serial_getc(struct udevice *dev)
        return readl(base + RDR_OFFSET(stm32f4));
 }
 
-static int stm32_serial_putc(struct udevice *dev, const char c)
+static int _stm32_serial_putc(fdt_addr_t base,
+                             struct stm32_uart_info *uart_info,
+                             const char c)
 {
-       struct stm32x7_serial_platdata *plat = dev_get_platdata(dev);
-       bool stm32f4 = plat->uart_info->stm32f4;
-       fdt_addr_t base = plat->base;
+       bool stm32f4 = uart_info->stm32f4;
 
        if ((readl(base + ISR_OFFSET(stm32f4)) & USART_ISR_FLAG_TXE) == 0)
                return -EAGAIN;
@@ -72,6 +82,13 @@ static int stm32_serial_putc(struct udevice *dev, const char 
c)
        return 0;
 }
 
+static int stm32_serial_putc(struct udevice *dev, const char c)
+{
+       struct stm32x7_serial_platdata *plat = dev_get_platdata(dev);
+
+       return _stm32_serial_putc(plat->base, plat->uart_info, c);
+}
+
 static int stm32_serial_pending(struct udevice *dev, bool input)
 {
        struct stm32x7_serial_platdata *plat = dev_get_platdata(dev);
@@ -86,18 +103,28 @@ static int stm32_serial_pending(struct udevice *dev, bool 
input)
                        USART_ISR_FLAG_TXE ? 0 : 1;
 }
 
+static void _stm32_serial_init(fdt_addr_t base,
+                              struct stm32_uart_info *uart_info)
+{
+       bool stm32f4 = uart_info->stm32f4;
+       u8 uart_enable_bit = uart_info->uart_enable_bit;
+
+       /* Disable uart-> enable fifo -> enable uart */
+       clrbits_le32(base + CR1_OFFSET(stm32f4), USART_CR1_RE | USART_CR1_TE |
+                    BIT(uart_enable_bit));
+       if (uart_info->has_fifo)
+               setbits_le32(base + CR1_OFFSET(stm32f4), USART_CR1_FIFOEN);
+       setbits_le32(base + CR1_OFFSET(stm32f4), USART_CR1_RE | USART_CR1_TE |
+                    BIT(uart_enable_bit));
+}
+
 static int stm32_serial_probe(struct udevice *dev)
 {
        struct stm32x7_serial_platdata *plat = dev_get_platdata(dev);
        struct clk clk;
-       fdt_addr_t base = plat->base;
        int ret;
-       bool stm32f4;
-       u8 uart_enable_bit;
 
        plat->uart_info = (struct stm32_uart_info *)dev_get_driver_data(dev);
-       stm32f4 = plat->uart_info->stm32f4;
-       uart_enable_bit = plat->uart_info->uart_enable_bit;
 
        ret = clk_get_by_index(dev, 0, &clk);
        if (ret < 0)
@@ -115,13 +142,7 @@ static int stm32_serial_probe(struct udevice *dev)
                return plat->clock_rate;
        };
 
-       /* Disable uart-> enable fifo-> enable uart */
-       clrbits_le32(base + CR1_OFFSET(stm32f4), USART_CR1_RE | USART_CR1_TE |
-                    BIT(uart_enable_bit));
-       if (plat->uart_info->has_fifo)
-               setbits_le32(base + CR1_OFFSET(stm32f4), USART_CR1_FIFOEN);
-       setbits_le32(base + CR1_OFFSET(stm32f4), USART_CR1_RE | USART_CR1_TE |
-                    BIT(uart_enable_bit));
+       _stm32_serial_init(plat->base, plat->uart_info);
 
        return 0;
 }
@@ -161,3 +182,43 @@ U_BOOT_DRIVER(serial_stm32) = {
        .probe = stm32_serial_probe,
        .flags = DM_FLAG_PRE_RELOC,
 };
+
+#ifdef CONFIG_DEBUG_UART_STM32
+#include <debug_uart.h>
+static inline struct stm32_uart_info *_debug_uart_info(void)
+{
+       struct stm32_uart_info *uart_info;
+
+#if defined(CONFIG_STM32F4)
+       uart_info = &stm32f4_info;
+#elif defined(CONFIG_STM32F7)
+       uart_info = &stm32f7_info;
+#else
+       uart_info = &stm32h7_info;
+#endif
+       return uart_info;
+}
+
+static inline void _debug_uart_init(void)
+{
+       fdt_addr_t base = CONFIG_DEBUG_UART_BASE;
+       struct stm32_uart_info *uart_info = _debug_uart_info();
+
+       _stm32_serial_init(base, uart_info);
+       _stm32_serial_setbrg(base, uart_info,
+                            CONFIG_DEBUG_UART_CLOCK,
+                            CONFIG_BAUDRATE);
+       printf("DEBUG done\n");
+}
+
+static inline void _debug_uart_putc(int c)
+{
+       fdt_addr_t base = CONFIG_DEBUG_UART_BASE;
+       struct stm32_uart_info *uart_info = _debug_uart_info();
+
+       while (_stm32_serial_putc(base, uart_info, c) == -EAGAIN)
+               WATCHDOG_RESET();
+}
+
+DEBUG_UART_FUNCS
+#endif
-- 
1.9.1

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