[PATCH V2 2/4] board: rockchip: Add Recovery Button for Anbernic RGxx3

[Chris Morgan]

From: Chris Morgan <macromorgan at hotmail.com>

Add support for users to enter recovery mode by holding the function
button when they power up the device.

Since the device has soldered eMMC and sometimes does not expose a clk
pin on the mainboard there is a small chance that a user who flashes a
bad bootloader may not be able to recover if the headers themselves
are valid. As a result this check is done during spl_early_init() to
ensure that it runs as early as possible, and it does so by directly
manipulating the ADC hardware in lieu of loading the ADC driver.

Ideally, once we have an open source TPL stage we can move this to
the TPL stage, so it will run even earlier. It may also be possible
to make this code "more portable", but at the tradeoff of requiring
to be run later in the boot process. For now it's done in a board
specific way to err on the side of "do it early".

Signed-off-by: Chris Morgan <macromorgan at hotmail.com>
---
 board/anbernic/rgxx3_rk3566/rgxx3-rk3566.c | 64 ++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/board/anbernic/rgxx3_rk3566/rgxx3-rk3566.c b/board/anbernic/rgxx3_rk3566/rgxx3-rk3566.c
index 3d0c614623..a93b11cd47 100644
--- a/board/anbernic/rgxx3_rk3566/rgxx3-rk3566.c
+++ b/board/anbernic/rgxx3_rk3566/rgxx3-rk3566.c
@@ -6,12 +6,14 @@
 #include <abuf.h>
 #include <adc.h>
 #include <asm/io.h>
+#include <command.h>
 #include <display.h>
 #include <dm.h>
 #include <dm/lists.h>
 #include <env.h>
 #include <fdt_support.h>
 #include <linux/delay.h>
+#include <linux/iopoll.h>
 #include <mipi_dsi.h>
 #include <mmc.h>
 #include <panel.h>
@@ -20,6 +22,8 @@
 #include <stdlib.h>
 #include <video_bridge.h>
 
+#define BOOT_BROM_DOWNLOAD	0xef08a53c
+
 #define GPIO0_BASE		0xfdd60000
 #define GPIO4_BASE		0xfe770000
 #define GPIO_SWPORT_DR_L	0x0000
@@ -33,6 +37,14 @@
 
 #define GPIO_WRITEMASK(bits)	((bits) << 16)
 
+#define SARADC_BASE		0xfe720000
+#define SARADC_DATA		0x0000
+#define SARADC_STAS		0x0004
+#define SARADC_ADC_STATUS	BIT(0)
+#define SARADC_CTRL		0x0008
+#define SARADC_INPUT_SRC_MSK	0x7
+#define SARADC_POWER_CTRL	BIT(3)
+
 #define DTB_DIR			"rockchip/"
 
 struct rg3xx_model {
@@ -118,12 +130,64 @@ static const struct rg353_panel rg353_panel_details[] = {
 	},
 };
 
+/*
+ * The device has internal eMMC, and while some devices have an exposed
+ * clk pin you can ground to force a bypass not all devices do. As a
+ * result it may be possible for some devices to become a perma-brick
+ * if a corrupted TPL or SPL stage with a valid header is flashed to
+ * the internal eMMC. Add functionality to read ADC channel 0 (the func
+ * button) as early as possible in the boot process to provide some
+ * protection against this. If we ever get an open TPL stage, we should
+ * consider moving this function there.
+ */
+void read_func_button(void)
+{
+	int ret;
+	u32 reg;
+
+	/* Turn off SARADC to reset it. */
+	writel(0, (SARADC_BASE + SARADC_CTRL));
+
+	/* Enable channel 0 and power on SARADC. */
+	writel(((0 & SARADC_INPUT_SRC_MSK) | SARADC_POWER_CTRL),
+	       (SARADC_BASE + SARADC_CTRL));
+
+	/*
+	 * Wait for data to be ready. Use timeout of 20000us from
+	 * rockchip_saradc driver.
+	 */
+	ret = readl_poll_timeout((SARADC_BASE + SARADC_STAS), reg,
+				 !(reg & SARADC_ADC_STATUS), 20000);
+	if (ret) {
+		printf("ADC Timeout");
+		return;
+	}
+
+	/* Read the data from the SARADC. */
+	reg = readl((SARADC_BASE + SARADC_DATA));
+
+	/* Turn the SARADC back off so it's ready to be used again. */
+	writel(0, (SARADC_BASE + SARADC_CTRL));
+
+	/*
+	 * If the value is less than 30 the button is being pressed.
+	 * Reset the device back into Rockchip download mode.
+	 */
+	if (reg <= 30) {
+		printf("download key pressed, entering download mode...");
+		writel(BOOT_BROM_DOWNLOAD, CONFIG_ROCKCHIP_BOOT_MODE_REG);
+		do_reset(NULL, 0, 0, NULL);
+	}
+};
+
 /*
  * Start LED very early so user knows device is on. Set color
  * to red.
  */
 void spl_board_init(void)
 {
+	read_func_button();
+
 	/* Set GPIO0_C5, GPIO0_C6, and GPIO0_C7 to output. */
 	writel(GPIO_WRITEMASK(GPIO_C7 | GPIO_C6 | GPIO_C5) | \
 	       (GPIO_C7 | GPIO_C6 | GPIO_C5),
-- 
2.34.1