[PATCH 4/4] board: rockchip: Add early ADC button detect for RGxx3

[Chris Morgan <macroalpha82@gmail.com>]

From: Chris Morgan <macromorgan@hotmail.com>

Add ADC button detect for early SPL stage for RGxx3 device. This is
important because on at least the RG353P and RG353V a clk pin is not
exposed that would allow us to take the eMMC out of the boot path.

Signed-off-by: Chris Morgan <macromorgan@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 5c57b902d1..099eea60c3 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>
@@ -19,6 +21,8 @@
 #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
@@ -32,6 +36,14 @@
 
 #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 {
@@ -157,12 +169,64 @@ 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