[PATCH v3] arm: rockchip: spl: Add hotkey detection support.

[Valentin Liu <valentinliu@icloud.com>]

Add a configurable Rockchip SPL hotkey feature that checks the
serial console during SPL startup.

Ctrl+B can be used to enter BootROM download (MASKROM) mode and
be widely used. We can add more boot mode support in future.

Add CONFIG_SPL_ROCKCHIP_HOTKEY to enable the feature and wait for
the serial port to be ready to receive input before checking for
hotkeys.

Signed-off-by: Valentin Liu <valentinliu@icloud.com>
---
Changes for v2:
- Simplify the dependencies of SPL_ROCKCHIP_HOTKEY.
- Remove the conditions for the newly added includes.
---
Changes for v3:
- Add a dummy spl_hotkey_init() to avoid undefined reference errors
  when building without CONFIG_SPL_ROCKCHIP_HOTKEY.

 arch/arm/mach-rockchip/Kconfig | 13 ++++++++++
 arch/arm/mach-rockchip/spl.c   | 44 ++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/arch/arm/mach-rockchip/Kconfig b/arch/arm/mach-rockchip/Kconfig
index 1a2e7847c9e..f2d2b5520ef 100644
--- a/arch/arm/mach-rockchip/Kconfig
+++ b/arch/arm/mach-rockchip/Kconfig
@@ -743,6 +743,19 @@ config TPL_ROCKCHIP_EARLYRETURN_TO_BROM
 config SPL_MMC
 	default y if !SPL_ROCKCHIP_BACK_TO_BROM
 
+config SPL_ROCKCHIP_HOTKEY
+	bool "SPL hotkey support"
+	depends on SPL_DM_RESET && SPL_SERIAL
+	help
+	  Enable hotkey detection during SPL booting stage.
+
+	  When enabled, SPL checks the serial console for a control
+	  character and can execute Rockchip-specific hotkey actions,
+	  such as entering BootROM download mode (MASKROM) with Ctrl+B.
+
+	  The hotkey is checked after the SPL console has been
+	  initialized.
+
 config ROCKCHIP_SPI_IMAGE
 	bool "Build a SPI image for rockchip"
 	help
diff --git a/arch/arm/mach-rockchip/spl.c b/arch/arm/mach-rockchip/spl.c
index e989c148079..0bcfb42c306 100644
--- a/arch/arm/mach-rockchip/spl.c
+++ b/arch/arm/mach-rockchip/spl.c
@@ -13,11 +13,14 @@
 #include <log.h>
 #include <mapmem.h>
 #include <ram.h>
+#include <serial.h>
 #include <spl.h>
+#include <asm/arch-rockchip/boot_mode.h>
 #include <asm/arch-rockchip/bootrom.h>
 #include <asm/arch-rockchip/timer.h>
 #include <asm/global_data.h>
 #include <asm/io.h>
+#include <linux/delay.h>
 #include <linux/bitops.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -107,6 +110,44 @@ __weak int arch_cpu_init(void)
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_SPL_ROCKCHIP_HOTKEY)
+static void rockchip_reset_from_hotkey(const int code)
+{
+	switch (code) {
+	case 0x02:
+		printf("SPL Hotkey: Ctrl+B: BootROM download!\n");
+		writel(BOOT_BROM_DOWNLOAD, CONFIG_ROCKCHIP_BOOT_MODE_REG);
+		do_reset(NULL, 0, 0, NULL);
+		/*NOTREACHED*/
+	default:
+		if (code <= 0x1a) /* 'z' */
+			printf("SPL Hotkey: Ctrl+%c\n", code + 'A' - 1);
+		else
+			printf("SPL Hotkey: Unknown code: 0x%x, ignore\n", code);
+	}
+}
+
+static void spl_hotkey_init(void)
+{
+	if (!gd || !(gd->flags & GD_FLG_HAVE_CONSOLE))
+		return;
+	if (gd->flags & GD_FLG_DISABLE_CONSOLE)
+		return;
+
+	/* Wait for the serial port to be ready to receive data. */
+	mdelay(100);
+
+	if (serial_tstc())
+		rockchip_reset_from_hotkey(serial_getc());
+	else
+		printf("SPL Hotkey: No key pressed, continue\n");
+}
+#else
+static void spl_hotkey_init(void)
+{
+}
+#endif
+
 void board_init_f(ulong dummy)
 {
 	int ret;
@@ -143,6 +184,9 @@ void board_init_f(ulong dummy)
 	}
 #endif
 	preloader_console_init();
+
+	if (IS_ENABLED(CONFIG_SPL_ROCKCHIP_HOTKEY))
+		spl_hotkey_init();
 }
 
 void spl_board_prepare_for_boot(void)
-- 
2.53.0