Preserve PSRAM QMI interface around flash ops (#2539)

The flash ROM routines seem to overwrite the QMI configuration we set for
PSRAM, rendering it unreadable after any erase or write or ID command.

Wrap the 4 flash control functions to preserve the QMI state on the
RP2350.  On the RP2040, simply pass through the call.

Fixes #2537

Author: earlephilhower

cores/rp2040/flash_wrapper.cpp

@@ -0,0 +1,75 @@
+/*
+    Flash wrappers to protect PSRAM access on the RP2350
+
+    Copyright (c) 2024 Earle F. Philhower, III <[email protected]>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include <hardware/flash.h>
+
+#ifdef PICO_RP2350
+#include <hardware/structs/qmi.h>
+#endif
+
+extern "C" {
+    extern void __real_flash_range_erase(uint32_t flash_offs, size_t count);
+    void __wrap_flash_range_erase(uint32_t flash_offs, size_t count) {
+#ifdef PICO_RP2350
+        auto s = qmi_hw->m[1];
+#endif
+        __real_flash_range_erase(flash_offs, count);
+#ifdef PICO_RP2350
+        qmi_hw->m[1] = s;
+        __compiler_memory_barrier();
+#endif
+    }
+
+    extern void __real_flash_range_program(uint32_t flash_offs, const uint8_t *data, size_t count);
+    void __wrap_flash_range_program(uint32_t flash_offs, const uint8_t *data, size_t count) {
+#ifdef PICO_RP2350
+        auto s = qmi_hw->m[1];
+#endif
+        __real_flash_range_program(flash_offs, data, count);
+#ifdef PICO_RP2350
+        qmi_hw->m[1] = s;
+        __compiler_memory_barrier();
+#endif
+    }
+
+    extern void __real_flash_get_unique_id(uint8_t *id_out);
+    void __wrap_flash_get_unique_id(uint8_t *id_out) {
+#ifdef PICO_RP2350
+        auto s = qmi_hw->m[1];
+#endif
+        __real_flash_get_unique_id(id_out);
+#ifdef PICO_RP2350
+        qmi_hw->m[1] = s;
+        __compiler_memory_barrier();
+#endif
+    }
+
+    extern void __real_flash_do_cmd(const uint8_t *txbuf, uint8_t *rxbuf, size_t count);
+    void __wrap_flash_do_cmd(const uint8_t *txbuf, uint8_t *rxbuf, size_t count) {
+#ifdef PICO_RP2350
+        auto s = qmi_hw->m[1];
+#endif
+        __real_flash_do_cmd(txbuf, rxbuf, count);
+#ifdef PICO_RP2350
+        qmi_hw->m[1] = s;
+        __compiler_memory_barrier();
+#endif
+    }
+};

lib/core_wrap.txt

@@ -67,3 +67,8 @@
 -Wl,--wrap=cyw43_tcpip_link_status
 -Wl,--wrap=cyw43_cb_tcpip_init
 -Wl,--wrap=cyw43_cb_tcpip_deinit
+
+-Wl,--wrap=flash_range_erase
+-Wl,--wrap=flash_range_program
+-Wl,--wrap=flash_get_unique_id
+-Wl,--wrap=flash_do_cmd