PoC: testapp: Call syscall accessing SPI flash

hw/application_fpga/fw/testapp/Makefile

@@ -43,6 +43,7 @@ all: testapp.bin
 
 TESTAPP_FMTFILES = \
 	$(P)/main.c \
+	$(P)/syscall.h
 
 TESTAPP_OBJS = \
 	$(P)/main.o \

hw/application_fpga/fw/testapp/main.c

@@ -6,8 +6,10 @@
 #include "../tk1/led.h"
 #include "../tk1/lib.h"
 #include "../tk1/proto.h"
+#include "../tk1/syscall_nrs.h"
 #include "../tk1/types.h"
 #include "../tk1_mem.h"
+#include "syscall.h"
 
 #define USBMODE_PACKET_SIZE 64
 
@@ -189,6 +191,16 @@ int main(void)
 		anyfailed = 1;
 	}
 
+	syscall_enable();
+
+	// Syscall should be able to access flash
+	puts("\r\nReading SPI flash capacity using syscall...\r\n");
+	int flash_capacity = syscall(TK1_SYSCALL_GET_FLASH_CAPACITY, 0);
+	if (flash_capacity != 0x14) {
+		failmsg("Expected SPI flash capacity: 0x14 (1 MByte)");
+		anyfailed = 1;
+	}
+
 	// Test FW_RAM.
 	*fw_ram = 0x21;
 	if (*fw_ram == 0x21) {

hw/application_fpga/fw/testapp/syscall.S

@@ -0,0 +1,94 @@
+// SPDX-FileCopyrightText: 2024 Tillitis AB <tillitis.se>
+// SPDX-License-Identifier: BSD-2-Clause
+
+#include "../tk1/picorv32/custom_ops.S"
+
+	.section ".text"
+	.globl syscall_enable
+	.globl syscall
+
+syscall_enable:
+	// Enable IRQs
+	li t0, 0x7fffffff // IRQ31 mask
+	picorv32_maskirq_insn(zero, t0) // Enable IRQs
+
+	ret
+
+syscall:
+	// Save registers to stack
+	addi sp, sp, -32*4
+	sw x0, 0*4(sp)
+	sw x1, 1*4(sp)
+	// x2 (sp) is assumed to be preserved by the interrupt handler.
+	sw x3, 3*4(sp)
+	sw x4, 4*4(sp)
+	sw x5, 5*4(sp)
+	sw x6, 6*4(sp)
+	sw x7, 7*4(sp)
+	sw x8, 8*4(sp)
+	sw x9, 9*4(sp)
+	// x10 (a0) will contain syscall return value. And should not be saved.
+	sw x11, 11*4(sp)
+	sw x12, 12*4(sp)
+	sw x13, 13*4(sp)
+	sw x14, 14*4(sp)
+	sw x15, 15*4(sp)
+	sw x16, 16*4(sp)
+	sw x17, 17*4(sp)
+	sw x18, 18*4(sp)
+	sw x19, 19*4(sp)
+	sw x20, 20*4(sp)
+	sw x21, 21*4(sp)
+	sw x22, 22*4(sp)
+	sw x23, 23*4(sp)
+	sw x24, 24*4(sp)
+	sw x25, 25*4(sp)
+	sw x26, 26*4(sp)
+	sw x27, 27*4(sp)
+	sw x28, 28*4(sp)
+	sw x29, 29*4(sp)
+	sw x30, 30*4(sp)
+	sw x31, 31*4(sp)
+
+	// Trigger syscall interrupt
+	li t0, (1 << 31)
+	and t0, a0, t0
+	li t1, 0xe1000000 // Syscall interrupt trigger address
+	sw zero, 0(t1) // Trigger interrupt
+
+	// Restore registers from stack
+	lw x0, 0*4(sp)
+	lw x1, 1*4(sp)
+	// x2 (sp) is assumed to be preserved by the interrupt handler.
+	lw x3, 3*4(sp)
+	lw x4, 4*4(sp)
+	lw x5, 5*4(sp)
+	lw x6, 6*4(sp)
+	lw x7, 7*4(sp)
+	lw x8, 8*4(sp)
+	lw x9, 9*4(sp)
+	// x10 (a0) contains syscall return value. And should not be destroyed.
+	lw x11, 11*4(sp)
+	lw x12, 12*4(sp)
+	lw x13, 13*4(sp)
+	lw x14, 14*4(sp)
+	lw x15, 15*4(sp)
+	lw x16, 16*4(sp)
+	lw x17, 17*4(sp)
+	lw x18, 18*4(sp)
+	lw x19, 19*4(sp)
+	lw x20, 20*4(sp)
+	lw x21, 21*4(sp)
+	lw x22, 22*4(sp)
+	lw x23, 23*4(sp)
+	lw x24, 24*4(sp)
+	lw x25, 25*4(sp)
+	lw x26, 26*4(sp)
+	lw x27, 27*4(sp)
+	lw x28, 28*4(sp)
+	lw x29, 29*4(sp)
+	lw x30, 30*4(sp)
+	lw x31, 31*4(sp)
+	addi sp, sp, 32*4
+
+	ret

hw/application_fpga/fw/testapp/syscall.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: 2024 Tillitis AB <tillitis.se>
+// SPDX-License-Identifier: BSD-2-Clause
+
+#include "../tk1/types.h"
+
+#ifndef TKEY_APP_SYSCALL_H
+#define TKEY_APP_SYSCALL_H
+
+void syscall_enable(void);
+int syscall(uint32_t number, uint32_t arg1);
+
+#endif

hw/application_fpga/fw/tk1/syscall.c

@@ -4,6 +4,7 @@
  */
 
 #include "../tk1/assert.h"
+#include "../tk1/flash.h"
 #include "../tk1/led.h"
 #include "../tk1/syscall_nrs.h"
 #include "../tk1/types.h"
@@ -24,6 +25,13 @@ int32_t syscall_handler(uint32_t syscall_nr, uint32_t arg1)
 	case TK1_SYSCALL_SET_LED:
 		set_led(arg1);
 		return 0;
+	case TK1_SYSCALL_GET_FLASH_CAPACITY: {
+		uint8_t jedec_id[3];
+		flash_release_powerdown();
+		flash_read_jedec_id(jedec_id);
+		flash_powerdown();
+		return jedec_id[2];
+	}
 	default:
 		assert(1 == 2);
 	}