[nrf noup] drivers: misc: nordic_vpr_launcher: Improve code relocation

Instead of copying whole partition dedicated for VPR decode end address
from the beginning of the binary code. Only code and certain portion of
data is copied (excluding noinit section). It reduces the boot time and
fixes issue where noinit section is overwritten after reset.

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

drivers/misc/nordic_vpr_launcher/nordic_vpr_launcher.c

@@ -30,19 +30,62 @@ struct nordic_vpr_launcher_config {
 #endif
 };
 
+/** @brief Decode rom size from the VPR code.
+ *
+ * Use VPR code, which at the beginning encodes address of __relocation_region_end,
+ * to calculate code that needs to be copied. Expecting following 2 instructions:
+ *   auipc gp,val
+ *   addi gp,gp val
+ *
+ * @param src_addr Source address.
+ * @param dst_addr Destination address.
+ * @param[out] size ROM size.
+ *
+ * @retval 0 on successful size decoding.
+ * @retval -EINVAL if size decoding failed.
+ */
+static int decode_size(uintptr_t src_addr, uintptr_t dst_addr, size_t *size)
+{
+	uint32_t *instr = (uint32_t *)src_addr;
+	uint32_t i0 = instr[0];
+	uint32_t i1 = instr[1];
+	uint32_t instr0 = i0 & BIT_MASK(7);
+	uint32_t rd0 = (i0 >> 7) & BIT_MASK(5);
+	uint32_t imm0 = i0 >> 12;
+	int imm1 = (int)i1 >> 20;
+
+	if ((instr0 != 0x17) && (rd0 != 3)) {
+		return -EINVAL;
+	}
+
+	uintptr_t relocation_addr_end = dst_addr + (imm0 << 12);
+
+	relocation_addr_end += imm1;
+	*size =  (size_t)(relocation_addr_end - dst_addr)+ 0;
+
+	return 0;
+}
+
 static int nordic_vpr_launcher_init(const struct device *dev)
 {
 	const struct nordic_vpr_launcher_config *config = dev->config;
-
 #if DT_ANY_INST_HAS_PROP_STATUS_OKAY(source_memory)
+	size_t size;
+	int err;
+
+	err = decode_size(config->src_addr, config->exec_addr, &size);
+	if (err < 0) {
+		size = config->size;
+	}
+
 	if (config->size > 0U) {
 		LOG_DBG("Loading VPR (%p) from %p to %p (%zu bytes)", config->vpr,
-			(void *)config->src_addr, (void *)config->exec_addr, config->size);
-		memcpy((void *)config->exec_addr, (void *)config->src_addr, config->size);
+			(void *)config->src_addr, (void *)config->exec_addr, size);
+		memcpy((void *)config->exec_addr, (void *)config->src_addr, size);
 #if defined(CONFIG_DCACHE)
 		LOG_DBG("Writing back cache with loaded VPR (from %p %zu bytes)",
-			(void *)config->exec_addr, config->size);
-		sys_cache_data_flush_range((void *)config->exec_addr, config->size);
+			(void *)config->exec_addr, size);
+		sys_cache_data_flush_range((void *)config->exec_addr, size);
 #endif
 	}
 #endif