rp2040: Add rp2350 specific mechanism for checking for double reset tap

It appears the rp2350 disables SRAM power when the RUN pin is pulled
low.  As a result, one can not store a code in regular memory to
detect if the RUN pin is pulled low multiple times.

Add a new CONFIG_HAVE_BOARD_CHECK_DOUBLE_RESET mechanism to allow the
board code to override the standard double reset checking code.
Implement an rp2350 specific check that uses the chip's POWMAN
chip_reset field to store/check a double reset condition.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/Kconfig

@@ -120,6 +120,9 @@ config BUILD_DEPLOYER
 config HAVE_CHIPID
     bool
     default n
+config HAVE_BOARD_CHECK_DOUBLE_RESET
+    bool
+    default n
 
 config KATAPULT_VERSION
     string

src/bootentry.c

@@ -32,11 +32,14 @@ check_button_pressed(void)
 #define DOUBLE_CLICK_MAX_US 500000
 
 // Check for a bootloader request via double tap of reset button
-static void
+static int
 check_double_reset(void)
 {
     if (!CONFIG_ENABLE_DOUBLE_RESET)
-        return;
+        return 0;
+    if (CONFIG_HAVE_BOARD_CHECK_DOUBLE_RESET)
+        // Use board specific detection mechanism
+        return board_check_double_reset();
     // Set request signature and delay - this enters the bootloader if
     // the reset button is double clicked
     udelay(DOUBLE_CLICK_MIN_US);
@@ -44,6 +47,7 @@ check_double_reset(void)
     udelay(DOUBLE_CLICK_MAX_US - DOUBLE_CLICK_MIN_US);
     // No reset, clear the bootup code
     set_bootup_code(0);
+    return 0;
 }
 
 // Check if bootloader or application should be started
@@ -60,8 +64,5 @@ bootentry_check(void)
         set_bootup_code(0);
         return 1;
     }
-    check_double_reset();
+    return check_double_reset();
-
-    // jump to app
-    return 0;
 }

src/bootentry.h

@@ -2,5 +2,6 @@
 #define __BOOTENTRY_H
 
 int bootentry_check(void);
+int board_check_double_reset(void);
 
 #endif // bootentry.h

src/rp2040/Kconfig

@@ -7,6 +7,7 @@ config RPXXXX_SELECT
     default y
     select HAVE_GPIO
     select HAVE_CHIPID
+    select HAVE_BOARD_CHECK_DOUBLE_RESET if MACH_RP2350
 
 config BOARD_DIRECTORY
     string

src/rp2040/Makefile

@@ -21,6 +21,7 @@ mcu-y += generic/armcm_irq.c generic/crc16_ccitt.c
 mcu-y += ../lib/pico-sdk/hardware/flash.c
 mcu-$(CONFIG_MACH_RP2040) += rp2040/timer.c rp2040/bootrom.c
 mcu-$(CONFIG_MACH_RP2350) += generic/armcm_timer.c rp2040/rp2350_bootrom.c
+mcu-$(CONFIG_MACH_RP2350) += rp2040/rp2350_dblreset.c
 
 src-y += generic/armcm_canboot.c $(mcu-y)
 src-$(CONFIG_USBSERIAL) += rp2040/usbserial.c generic/usb_cdc.c rp2040/chipid.c

src/rp2040/rp2350_dblreset.c

@@ -0,0 +1,31 @@
+// rp2350 specific handling for checking if double reset occurred
+//
+// Copyright (C) 2024  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stdint.h> // uint32_t
+#include "bootentry.h" // board_check_double_reset
+#include "canboot.h" // udelay
+#include "hardware/structs/powman.h" // powman_hw
+
+#define DOUBLE_CLICK_MIN_US 10000
+#define DOUBLE_CLICK_MAX_US 500000
+
+int
+board_check_double_reset(void)
+{
+    if (powman_hw->chip_reset & POWMAN_CHIP_RESET_DOUBLE_TAP_BITS) {
+        // Double reset detected - clear flag and enter bootloader
+        powman_hw->chip_reset = 0x5afe0000;
+        return 1;
+    }
+    // Initial delay (reset in under 10ms isn't a "double tap")
+    udelay(DOUBLE_CLICK_MIN_US);
+    // Set the DOUBLE_TAP_BITS bits
+    powman_hw->chip_reset = 0x5afe0001;
+    udelay(DOUBLE_CLICK_MAX_US - DOUBLE_CLICK_MIN_US);
+    // No reset, clear the DOUBLE_TAP_BITS bits
+    powman_hw->chip_reset = 0x5afe0000;
+    return 0;
+}