feat(gps): add timer-based assisted reacquisition

Remove the fixed pseudorange start offset, preserve per-PRN navigation assistance across RF loss and power cycles, and seed coherent navigation measurement phase on reacquisition. Add full LNAV almanac visibility scheduling, power-safe QSPI journaling, RF-domain reset isolation, and PPS Gray CDC hardening with Linux, sanitizer, RTL, and end-to-end coverage.

soc/software/bsp/drivers/spi_flash.c

@@ -3,6 +3,8 @@
 #include "bsp/mmio.h"
 #include "bsp/soc.h"
 
+#include <stddef.h>
+
 #define SPI_CTRL  (BSP_SPI_BASE + 0x00u)
 #define SPI_TX    (BSP_SPI_BASE + 0x04u)
 #define SPI_RX    (BSP_SPI_BASE + 0x08u)
@@ -11,6 +13,15 @@
 #define SPI_CTRL_BUSY 0x1u
 #define SPI_CTRL_CSN  0x2u
 
+#define FLASH_CMD_WRITE_ENABLE 0x06u
+#define FLASH_CMD_READ_STATUS  0x05u
+#define FLASH_CMD_PAGE_PROGRAM_4B 0x12u
+#define FLASH_CMD_SECTOR_ERASE_4B 0xdcu
+#define FLASH_STATUS_WIP 0x01u
+#define FLASH_STATUS_WEL 0x02u
+#define FLASH_PAGE_SIZE 256u
+#define FLASH_READY_POLL_LIMIT 5000000u
+
 static void delay_cycles(uint32_t cycles)
 {
   for (volatile uint32_t i = 0; i < cycles; ++i) {
@@ -47,6 +58,32 @@ static void flash_cmd(uint8_t cmd)
   spi_select(0);
 }
 
+static uint8_t flash_read_status(void)
+{
+  uint8_t status;
+  spi_select(1);
+  (void)spi_xfer8(FLASH_CMD_READ_STATUS);
+  status = spi_xfer8(0u);
+  spi_select(0);
+  return status;
+}
+
+static bool flash_write_enable(void)
+{
+  flash_cmd(FLASH_CMD_WRITE_ENABLE);
+  return (flash_read_status() & FLASH_STATUS_WEL) != 0u;
+}
+
+static bool flash_wait_operation(void)
+{
+  for(uint32_t poll = 0u; poll < FLASH_READY_POLL_LIMIT; ++poll) {
+    if((flash_read_status() & FLASH_STATUS_WIP) == 0u) {
+      return true;
+    }
+  }
+  return false;
+}
+
 void bsp_spi_flash_init(void)
 {
   bsp_write32(SPI_CTRL, SPI_CTRL_CSN);
@@ -88,3 +125,42 @@ void bsp_spi_flash_read(uint32_t flash_addr, void *dst, uint32_t len)
   }
   spi_select(0);
 }
+
+bool bsp_spi_flash_program_page(
+  uint32_t flash_addr, const void *src, uint32_t len)
+{
+  if((src == NULL) || (len == 0u) || (len > FLASH_PAGE_SIZE) ||
+     ((flash_addr & (FLASH_PAGE_SIZE - 1u)) + len > FLASH_PAGE_SIZE) ||
+     !flash_write_enable()) {
+    return false;
+  }
+
+  const uint8_t *data = (const uint8_t *)src;
+  spi_select(1);
+  (void)spi_xfer8(FLASH_CMD_PAGE_PROGRAM_4B);
+  (void)spi_xfer8((uint8_t)(flash_addr >> 24));
+  (void)spi_xfer8((uint8_t)(flash_addr >> 16));
+  (void)spi_xfer8((uint8_t)(flash_addr >> 8));
+  (void)spi_xfer8((uint8_t)flash_addr);
+  for(uint32_t i = 0u; i < len; ++i) {
+    (void)spi_xfer8(data[i]);
+  }
+  spi_select(0);
+  return flash_wait_operation();
+}
+
+bool bsp_spi_flash_erase_sector(uint32_t flash_addr)
+{
+  if(!flash_write_enable()) {
+    return false;
+  }
+
+  spi_select(1);
+  (void)spi_xfer8(FLASH_CMD_SECTOR_ERASE_4B);
+  (void)spi_xfer8((uint8_t)(flash_addr >> 24));
+  (void)spi_xfer8((uint8_t)(flash_addr >> 16));
+  (void)spi_xfer8((uint8_t)(flash_addr >> 8));
+  (void)spi_xfer8((uint8_t)flash_addr);
+  spi_select(0);
+  return flash_wait_operation();
+}