rockchip: rk3399-puma: add code to allow forcing a power-on reset

The reset circuitry in the RK3399 only resets 'almost all logic' when
a software reset is performed.  To make our software maintenance
easier in the future, we want to have the option (controlled by a DTS
property) to force all reset causes other than a power-on reset to
trigger a power-on reset via a GPIO trigger.

This adds the necessary support to the rk3399-puma (i.e. RK3399-Q7)
board-support and the documentation for the new property
(sysreset-gpio) within the /config-node.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Klaus Goger <klaus.goger@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

board/theobroma-systems/puma_rk3399/puma-rk3399.c

@@ -11,7 +11,10 @@
 #include <usb.h>
 #include <dm/pinctrl.h>
 #include <dm/uclass-internal.h>
+#include <asm/gpio.h>
 #include <asm/setup.h>
+#include <asm/arch/clock.h>
+#include <asm/arch/cru_rk3399.h>
 #include <asm/arch/periph.h>
 #include <power/regulator.h>
 #include <u-boot/sha256.h>
@@ -33,9 +36,50 @@ int board_init(void)
 	return 0;
 }
 
+static void rk3399_force_power_on_reset(void)
+{
+	ofnode node;
+	struct gpio_desc sysreset_gpio;
+
+	debug("%s: trying to force a power-on reset\n", __func__);
+
+	node = ofnode_path("/config");
+	if (!ofnode_valid(node)) {
+		debug("%s: no /config node?\n", __func__);
+		return;
+	}
+
+	if (gpio_request_by_name_nodev(node, "sysreset-gpio", 0,
+				       &sysreset_gpio, GPIOD_IS_OUT)) {
+		debug("%s: could not find a /config/sysreset-gpio\n", __func__);
+		return;
+	}
+
+	dm_gpio_set_value(&sysreset_gpio, 1);
+}
+
 void spl_board_init(void)
 {
 	int  ret;
+	struct rk3399_cru *cru = rockchip_get_cru();
+
+	/*
+	 * The RK3399 resets only 'almost all logic' (see also in the TRM
+	 * "3.9.4 Global software reset"), when issuing a software reset.
+	 * This may cause issues during boot-up for some configurations of
+	 * the application software stack.
+	 *
+	 * To work around this, we test whether the last reset reason was
+	 * a power-on reset and (if not) issue an overtemp-reset to reset
+	 * the entire module.
+	 *
+	 * While this was previously fixed by modifying the various places
+	 * that could generate a software reset (e.g. U-Boot's sysreset
+	 * driver, the ATF or Linux), we now have it here to ensure that
+	 * we no longer have to track this through the various components.
+	 */
+	if (cru->glb_rst_st != 0)
+		rk3399_force_power_on_reset();
 
 	/*
 	 * Turning the eMMC and SPI back on (if disabled via the Qseven

doc/device-tree-bindings/config.txt

@@ -46,3 +46,9 @@ u-boot,spl-payload-offset
 	If present (and SPL is controlled by the device-tree), this allows
 	to override the CONFIG_SYS_SPI_U_BOOT_OFFS setting using a value
 	from the device-tree.
+
+sysreset-gpio
+	If present (and supported by the specific board), indicates a
+	GPIO that can be set to trigger a system reset.  It is assumed
+	that such a system reset will effect a complete platform reset,
+	being roughly equivalent to a power-on reset.