Add 'user-flash' CLI argument

doc/vendors/gowin.rst

@@ -62,3 +62,17 @@ It's possible to flash external SPI Flash (connected to MSPI) in bscan mode by u
 
   Gowin's FPGA may fails to be detected if **JTAGSEL_N** (pin 08 for *GW1N-4K*) is used as a GPIO.
   To recover you have to pull down this pin (before power up) to recover JTAG interface (*UG292 - JTAGSELL_N section*).
+
+User Flash
+----------
+
+.. ATTENTION::
+  User Flash support is based on reverse engineering of the JTAG protocol. This functionality should be considered
+  experimental as it hasn't been thoroughly tested, and may in some circumstances destroy your device.
+
+Gowin FPGA come with extra flash space that can be read and written from the programmable logic ("User Flash"). This
+flash section can also be programmed via the JTAG interface:
+
+.. code-block:: bash
+
+    openFPGALoader --write-flash /path/to/bitstream.fs --user-flash /path/to/flash.bin

src/gowin.cpp

@@ -77,8 +77,8 @@ using namespace std;
 
 Gowin::Gowin(Jtag *jtag, const string filename, const string &file_type, std::string mcufw,
 		Device::prog_type_t prg_type, bool external_flash,
-		bool verify, int8_t verbose): Device(jtag, filename, file_type,
-		verify, verbose),
+		bool verify, int8_t verbose, const std::string& user_flash)
+	: Device(jtag, filename, file_type, verify, verbose),
 		SPIInterface(filename, verbose, 0, verify, false, false),
 		_idcode(0), is_gw1n1(false), is_gw1n4(false), is_gw1n9(false),
 		is_gw2a(false), is_gw5a(false),

src/gowin.hpp

@@ -22,7 +22,8 @@ class Gowin: public Device, SPIInterface {
 	public:
 		Gowin(Jtag *jtag, std::string filename, const std::string &file_type,
 				std::string mcufw, Device::prog_type_t prg_type,
-				bool external_flash, bool verify, int8_t verbose);
+				bool external_flash, bool verify, int8_t verbose,
+				const std::string& user_flash);
 		uint32_t idCode() override;
 		void reset() override;
 		void program(unsigned int offset, bool unprotect_flash) override;

src/main.cpp

@@ -97,6 +97,7 @@ struct arguments {
 	bool read_dna;
 	bool read_xadc;
 	string read_register;
+	string user_flash;
 };
 
 int run_xvc_server(const struct arguments &args, const cable_t &cable,
@@ -582,7 +583,7 @@ int main(int argc, char **argv)
 				args.verify, args.verbose);
 		} else if (fab == "Gowin") {
 			fpga = new Gowin(jtag, args.bit_file, args.file_type, args.mcufw,
-				args.prg_type, args.external_flash, args.verify, args.verbose);
+				args.prg_type, args.external_flash, args.verify, args.verbose, args.user_flash);
 		} else if (fab == "lattice") {
 			fpga = new Lattice(jtag, args.bit_file, args.file_type,
 				args.prg_type, args.flash_sector, args.verify, args.verbose, args.skip_load_bridge, args.skip_reset);
@@ -871,6 +872,8 @@ int parse_opt(int argc, char **argv, struct arguments *args,
 				cxxopts::value<bool>(args->read_xadc))
 			("read-register", "Read Status Register(Xilinx FPGA only)",
 				cxxopts::value<string>(rd_reg))
+			("user-flash", "User flash file (Gowin LittleBee FPGA only)",
+				cxxopts::value<string>(args->user_flash))
 			("V,Version", "Print program version");
 
 		options.parse_positional({"bitstream"});