rp2040: Move chipid reading to bootrom.c

Rewrite chipid.c so that it contains just the USB and canbus id
manipulation code.  Move the low-level chipid reading to bootrom.c.

Also, introduce a new bootrom_reboot_usb_bootloader() function in
bootrom.c so that the main.c code does not need to know the specifics
of rebooting into the bootrom.

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

4 files changed, 120 insertions, 108 deletions

diff --git a/src/rp2040/bootrom.c b/src/rp2040/bootrom.c
index 6e6c46e9..e54bdcc2 100644
--- a/src/rp2040/bootrom.c
+++ b/src/rp2040/bootrom.c
@@ -6,7 +6,10 @@
 
 #include <stdint.h> // uint16_t, uint32_t, uintptr_t
 #include <string.h> // memcpy
+#include "board/irq.h" // irq_disable, irq_enable
 #include "compiler.h" // noinline, __section
+#include "hardware/structs/ioqspi.h" // ioqspi_hw
+#include "hardware/structs/ssi.h" // ssi_hw
 #include "internal.h" // _ramfunc
 
 #define ROM_TABLE_CODE(c1, c2) ((c1) | ((c2) << 8))
@@ -35,7 +38,7 @@ rom_func_lookup(uint32_t code)
   return fn(table, code);
 }
 
-void _ramfunc
+static void _ramfunc
 reset_to_usb_boot(uint32_t gpio_activity_pin_mask
                   , uint32_t disable_interface_mask)
 {
@@ -43,23 +46,129 @@ reset_to_usb_boot(uint32_t gpio_activity_pin_mask
   fn(gpio_activity_pin_mask, disable_interface_mask);
 }
 
-void _ramfunc
+static void _ramfunc
 connect_internal_flash(void)
 {
   void (*fn)(void) = rom_func_lookup(ROM_TABLE_CODE('I', 'F'));
   fn();
 }
 
-void _ramfunc
+static void _ramfunc
 flash_exit_xip(void)
 {
   void (*fn)(void) = rom_func_lookup(ROM_TABLE_CODE('E', 'X'));
   fn();
 }
 
-void _ramfunc
+static void _ramfunc
 flash_flush_cache(void)
 {
   void (*fn)(void) = rom_func_lookup(ROM_TABLE_CODE('F', 'C'));
   fn();
 }
+
+
+/****************************************************************
+ * Reboot to USB rom bootloader
+ ****************************************************************/
+
+void
+bootrom_reboot_usb_bootloader(void)
+{
+    reset_to_usb_boot(0, 0);
+}
+
+
+/****************************************************************
+ * Unique id reading
+ ****************************************************************/
+
+// Functions for reading out the flash chip ID. Adapted from the official
+// Pi SDK.
+
+static void _ramfunc
+flash_cs_force(int high)
+{
+    uint32_t field_val = high ?
+        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_VALUE_HIGH :
+        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_VALUE_LOW;
+    hw_write_masked(&ioqspi_hw->io[1].ctrl,
+        field_val << IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_LSB,
+        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_BITS
+    );
+}
+
+// To re-enable XIP we need to call flash_enter_xip. It's available in the
+// bootrom, but that version is a generic one that works for most devices and
+// the tradeoff for that is enabling a low performance mode.
+// Instead we copy out the boot2 XIP enabling stage, and save it in RAM
+// so we can call it later on.
+
+#define BOOT2_SIZE 0x100
+
+static uint8_t boot2_copy[BOOT2_SIZE] __aligned(16);
+
+static void
+flash_enter_xip_prepare(void)
+{
+  void * volatile target = (void *)XIP_BASE; // Avoids warning
+  memcpy(boot2_copy, target, BOOT2_SIZE);
+  barrier();
+}
+
+static void _ramfunc
+flash_enter_xip_perform(void)
+{
+  ((void (*)(void))boot2_copy+1)();
+}
+
+#define FLASH_RUID_CMD         0x4B
+#define FLASH_RUID_DUMMY_BYTES 4
+#define FLASH_RUID_DATA_BYTES  8
+#define FLASH_RUID_TOTAL_BYTES (1+FLASH_RUID_DUMMY_BYTES+FLASH_RUID_DATA_BYTES)
+
+void _ramfunc
+bootrom_read_unique_id(uint8_t *out, uint32_t maxlen)
+{
+    uint8_t txbuf[FLASH_RUID_TOTAL_BYTES] = {0};
+    uint8_t rxbuf[FLASH_RUID_TOTAL_BYTES] = {0};
+
+    uint8_t *txptr = txbuf;
+    uint8_t *rxptr = rxbuf;
+
+    int tx_remaining = FLASH_RUID_TOTAL_BYTES;
+    int rx_remaining = FLASH_RUID_TOTAL_BYTES;
+
+    txbuf[0] = FLASH_RUID_CMD;
+
+    // Set up flash so we can work with it without XIP getting in the way
+    flash_enter_xip_prepare();
+    irq_disable();
+    barrier();
+    connect_internal_flash();
+    flash_exit_xip();
+    flash_cs_force(0);
+
+    while (tx_remaining || rx_remaining) {
+        uint32_t flags = ssi_hw->sr;
+        int can_put = !!(flags & SSI_SR_TFNF_BITS);
+        int can_get = !!(flags & SSI_SR_RFNE_BITS);
+        if (can_put && tx_remaining) {
+            ssi_hw->dr0 = *txptr++;
+            tx_remaining--;
+        }
+        if (can_get && rx_remaining) {
+            *rxptr++ = (uint8_t)ssi_hw->dr0;
+            --rx_remaining;
+        }
+    }
+
+    // Restore XIP
+    flash_cs_force(1);
+    flash_flush_cache();
+    flash_enter_xip_perform();
+    barrier();
+    irq_enable();
+
+    memcpy(out, rxbuf+1+FLASH_RUID_DUMMY_BYTES, FLASH_RUID_DATA_BYTES);
+}
diff --git a/src/rp2040/chipid.c b/src/rp2040/chipid.c
index 80182f60..75d6e385 100644
--- a/src/rp2040/chipid.c
+++ b/src/rp2040/chipid.c
@@ -1,19 +1,15 @@
 // Support for extracting the hardware chip id on rp2040
 //
-// Copyright (C) 2021  Lasse Dalegaard <dalegaard@gmail.com>
+// Copyright (C) 2019-2024  Kevin O'Connor <kevin@koconnor.net>
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#include <string.h> // memcpy
 #include "autoconf.h" // CONFIG_USB_SERIAL_NUMBER_CHIPID
-#include "board/irq.h" // irq_disable, irq_enable
 #include "board/canserial.h" // canserial_set_uuid
 #include "generic/usb_cdc.h" // usb_fill_serial
 #include "generic/usbstd.h" // usb_string_descriptor
+#include "internal.h" // bootrom_read_unique_id
 #include "sched.h" // DECL_INIT
-#include "hardware/structs/ioqspi.h" // ioqspi_hw
-#include "hardware/structs/ssi.h" // ssi_hw
-#include "internal.h"
 
 #define CHIP_UID_LEN 8
 
@@ -28,104 +24,14 @@ usbserial_get_serialid(void)
     return &cdc_chipid.desc;
 }
 
-// Functions for reading out the flash chip ID. Adapted from the official
-// Pi SDK.
-
-static void _ramfunc
-flash_cs_force(int high)
-{
-    uint32_t field_val = high ?
-        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_VALUE_HIGH :
-        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_VALUE_LOW;
-    hw_write_masked(&ioqspi_hw->io[1].ctrl,
-        field_val << IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_LSB,
-        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_BITS
-    );
-}
-
-// To re-enable XIP we need to call flash_enter_xip. It's available in the
-// bootrom, but that version is a generic one that works for most devices and
-// the tradeoff for that is enabling a low performance mode.
-// Instead we copy out the boot2 XIP enabling stage, and save it in RAM
-// so we can call it later on.
-
-#define BOOT2_SIZE 0x100
-
-static uint8_t boot2_copy[BOOT2_SIZE] __aligned(16);
-
-static void
-flash_enter_xip_prepare(void)
-{
-  void * volatile target = (void *)XIP_BASE; // Avoids warning
-  memcpy(boot2_copy, target, BOOT2_SIZE);
-  barrier();
-}
-
-static void _ramfunc
-flash_enter_xip_perform(void)
-{
-  ((void (*)(void))boot2_copy+1)();
-}
-
-#define FLASH_RUID_CMD         0x4B
-#define FLASH_RUID_DUMMY_BYTES 4
-#define FLASH_RUID_DATA_BYTES  8
-#define FLASH_RUID_TOTAL_BYTES (1+FLASH_RUID_DUMMY_BYTES+FLASH_RUID_DATA_BYTES)
-
-static void _ramfunc
-read_unique_id(uint8_t *out)
-{
-    uint8_t txbuf[FLASH_RUID_TOTAL_BYTES] = {0};
-    uint8_t rxbuf[FLASH_RUID_TOTAL_BYTES] = {0};
-
-    uint8_t *txptr = txbuf;
-    uint8_t *rxptr = rxbuf;
-
-    int tx_remaining = FLASH_RUID_TOTAL_BYTES;
-    int rx_remaining = FLASH_RUID_TOTAL_BYTES;
-
-    txbuf[0] = FLASH_RUID_CMD;
-
-    // Set up flash so we can work with it without XIP getting in the way
-    flash_enter_xip_prepare();
-    irq_disable();
-    barrier();
-    connect_internal_flash();
-    flash_exit_xip();
-    flash_cs_force(0);
-
-    while (tx_remaining || rx_remaining) {
-        uint32_t flags = ssi_hw->sr;
-        int can_put = !!(flags & SSI_SR_TFNF_BITS);
-        int can_get = !!(flags & SSI_SR_RFNE_BITS);
-        if (can_put && tx_remaining) {
-            ssi_hw->dr0 = *txptr++;
-            tx_remaining--;
-        }
-        if (can_get && rx_remaining) {
-            *rxptr++ = (uint8_t)ssi_hw->dr0;
-            --rx_remaining;
-        }
-    }
-
-    // Restore XIP
-    flash_cs_force(1);
-    flash_flush_cache();
-    flash_enter_xip_perform();
-    barrier();
-    irq_enable();
-
-    memcpy(out, rxbuf+1+FLASH_RUID_DUMMY_BYTES, FLASH_RUID_DATA_BYTES);
-}
-
 void
 chipid_init(void)
 {
     if (!(CONFIG_USB_SERIAL_NUMBER_CHIPID || CONFIG_CANBUS))
         return;
 
-    uint8_t data[8] = {0};
-    read_unique_id(data);
+    uint8_t data[CHIP_UID_LEN] = {};
+    bootrom_read_unique_id(data, sizeof(data));
 
     if (CONFIG_USB_SERIAL_NUMBER_CHIPID)
         usb_fill_serial(&cdc_chipid.desc, ARRAY_SIZE(cdc_chipid.data), data);
diff --git a/src/rp2040/internal.h b/src/rp2040/internal.h
index 010318a6..da5b0a5b 100644
--- a/src/rp2040/internal.h
+++ b/src/rp2040/internal.h
@@ -14,11 +14,8 @@ void enable_pclock(uint32_t reset_bit);
 int is_enabled_pclock(uint32_t reset_bit);
 uint32_t get_pclock_frequency(uint32_t reset_bit);
 void gpio_peripheral(uint32_t gpio, int func, int pull_up);
-void reset_to_usb_boot(uint32_t gpio_activity_pin_mask
-                       , uint32_t disable_interface_mask);
-void connect_internal_flash(void);
-void flash_exit_xip(void);
-void flash_flush_cache(void);
+void bootrom_reboot_usb_bootloader(void);
+void bootrom_read_unique_id(uint8_t *out, uint32_t maxlen);
 
 // Force a function to run from ram
 #define UNIQSEC __FILE__ "." __stringify(__LINE__)
diff --git a/src/rp2040/main.c b/src/rp2040/main.c
index ed84e6e0..95fa5f15 100644
--- a/src/rp2040/main.c
+++ b/src/rp2040/main.c
@@ -51,7 +51,7 @@ bootloader_request(void)
     try_request_canboot();
     // Use the bootrom-provided code to reset into BOOTSEL mode
     if (CONFIG_MACH_RP2040)
-        reset_to_usb_boot(0, 0);
+        bootrom_reboot_usb_bootloader();
 }