fel: Report FEL stack pointers

This is may be useful when adding support for new SoC variants.
We want to be sure that the IRQ stack and the regular stack both
reside at predictable locations in SRAM and such extra diagnostic
message can confirm this.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>

fel.c

@@ -485,6 +485,43 @@ void aw_enable_l2_cache(libusb_device_handle *usb)
 	aw_fel_execute(usb, FEL_EXEC_SCRATCH_AREA);
 }
 
+void aw_get_stackinfo(libusb_device_handle *usb, uint32_t *sp_irq, uint32_t *sp)
+{
+	uint32_t results[2] = { 0 };
+#if 0
+	/* Does not work on Cortex-A8 (needs Virtualization Extensions) */
+	uint32_t arm_code[] = {
+		htole32(0xe1010300), /* mrs        r0, SP_irq                */
+		htole32(0xe58f0004), /* str        r0, [pc, #4]              */
+		htole32(0xe58fd004), /* str        sp, [pc, #4]              */
+		htole32(0xe12fff1e), /* bx         lr                        */
+	};
+
+	aw_fel_write(usb, arm_code, FEL_EXEC_SCRATCH_AREA, sizeof(arm_code));
+	aw_fel_execute(usb, FEL_EXEC_SCRATCH_AREA);
+	aw_fel_read(usb, FEL_EXEC_SCRATCH_AREA + 0x10, results, 8);
+#else
+	/* Works everywhere */
+	uint32_t arm_code[] = {
+		htole32(0xe10f0000), /* mrs        r0, CPSR                  */
+		htole32(0xe3c0101f), /* bic        r1, r0, #31               */
+		htole32(0xe3811012), /* orr        r1, r1, #18               */
+		htole32(0xe121f001), /* msr        CPSR_c, r1                */
+		htole32(0xe1a0100d), /* mov        r1, sp                    */
+		htole32(0xe121f000), /* msr        CPSR_c, r0                */
+		htole32(0xe58f1004), /* str        r1, [pc, #4]              */
+		htole32(0xe58fd004), /* str        sp, [pc, #4]              */
+		htole32(0xe12fff1e), /* bx         lr                        */
+	};
+
+	aw_fel_write(usb, arm_code, FEL_EXEC_SCRATCH_AREA, sizeof(arm_code));
+	aw_fel_execute(usb, FEL_EXEC_SCRATCH_AREA);
+	aw_fel_read(usb, FEL_EXEC_SCRATCH_AREA + 0x24, results, 8);
+#endif
+	*sp_irq = le32toh(results[0]);
+	*sp     = le32toh(results[1]);
+}
+
 uint32_t aw_get_ttbr0(libusb_device_handle *usb)
 {
 	uint32_t ttbr0 = 0;
@@ -496,7 +533,7 @@ uint32_t aw_get_ttbr0(libusb_device_handle *usb)
 
 	aw_fel_write(usb, arm_code, FEL_EXEC_SCRATCH_AREA, sizeof(arm_code));
 	aw_fel_execute(usb, FEL_EXEC_SCRATCH_AREA);
-	aw_fel_read(usb, 0x2014, &ttbr0, sizeof(ttbr0));
+	aw_fel_read(usb, FEL_EXEC_SCRATCH_AREA + 0x14, &ttbr0, sizeof(ttbr0));
 	ttbr0 = le32toh(ttbr0);
 	return ttbr0;
 }
@@ -512,7 +549,7 @@ uint32_t aw_get_sctlr(libusb_device_handle *usb)
 
 	aw_fel_write(usb, arm_code, FEL_EXEC_SCRATCH_AREA, sizeof(arm_code));
 	aw_fel_execute(usb, FEL_EXEC_SCRATCH_AREA);
-	aw_fel_read(usb, 0x2014, &sctlr, sizeof(sctlr));
+	aw_fel_read(usb, FEL_EXEC_SCRATCH_AREA + 0x14, &sctlr, sizeof(sctlr));
 	sctlr = le32toh(sctlr);
 	return sctlr;
 }
@@ -642,6 +679,7 @@ void aw_fel_write_and_execute_spl(libusb_device_handle *usb,
 	char header_signature[9] = { 0 };
 	size_t i, thunk_size;
 	uint32_t *thunk_buf;
+	uint32_t sp, sp_irq;
 	uint32_t spl_checksum, spl_len, spl_len_limit = SPL_LEN_LIMIT;
 	uint32_t *buf32 = (uint32_t *)buf;
 	uint32_t written = 0;
@@ -679,6 +717,9 @@ void aw_fel_write_and_execute_spl(libusb_device_handle *usb,
 		aw_enable_l2_cache(usb);
 	}
 
+	aw_get_stackinfo(usb, &sp_irq, &sp);
+	pr_info("Stack pointers: sp_irq=0x%08X, sp=0x%08X\n", sp_irq, sp);
+
 	tt = aw_backup_and_disable_mmu(usb);
 
 	swap_buffers = sram_info->swap_buffers;