driver: flash: esp32: fix unaligned read

Fix flash read operation to account for all unaligned
scenarios, i.e, address, buffer and length. This is needed
when using flash APIs provided in ROM.

This also removes the unaligned flash write call as it
expects aligned values only.

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>

Author: sylvioalves

drivers/flash/flash_esp32.c

@@ -76,26 +76,67 @@ static inline void flash_esp32_sem_give(const struct device *dev)
 #include <stdint.h>
 #include <string.h>
 
+#ifdef CONFIG_MCUBOOT
+#define READ_BUFFER_SIZE 32
+static bool flash_esp32_is_aligned(off_t address, void *buffer, size_t length)
+{
+	/* check if address, buffer pointer, and length are 4-byte aligned */
+	return ((address & 3) == 0) && (((uintptr_t)buffer & 3) == 0) && ((length & 3) == 0);
+}
+#endif
+
 static int flash_esp32_read(const struct device *dev, off_t address, void *buffer, size_t length)
 {
 	int ret = 0;
 
 #ifdef CONFIG_MCUBOOT
-	/* ensure everything is 4-byte aligned */
-	size_t aligned_length = ROUND_UP(length, 4);
-	off_t aligned_address = ROUND_DOWN(address, 4);
-	size_t address_offset = address - aligned_address;
-	uint32_t temp_buf[aligned_length / 4];
-
-	if (!esp_flash_encryption_enabled()) {
-		ret = esp_rom_flash_read(aligned_address, temp_buf, aligned_length, false);
-	} else {
-		ret = esp_rom_flash_read(aligned_address, temp_buf, aligned_length, true);
+	uint8_t *dest_ptr = (uint8_t *)buffer;
+	size_t remaining = length;
+	size_t copy_size = 0;
+	size_t aligned_size = 0;
+	bool allow_decrypt = esp_flash_encryption_enabled();
+
+	if (flash_esp32_is_aligned(address, buffer, length)) {
+		ret = esp_rom_flash_read(address, buffer, length, allow_decrypt);
+		return (ret == ESP_OK) ? 0 : -EIO;
 	}
 
-	memcpy((void *)buffer, ((uint8_t *)temp_buf) + address_offset, length);
-#else
+	/* handle unaligned reading */
+	uint8_t __aligned(4) temp_buf[READ_BUFFER_SIZE + 8];
+	while (remaining > 0) {
+		size_t addr_offset = address & 3;
+		size_t buf_offset = (uintptr_t)dest_ptr & 3;
+
+		copy_size = (remaining > READ_BUFFER_SIZE) ? READ_BUFFER_SIZE : remaining;
+
+		if (addr_offset == 0 && buf_offset == 0 && copy_size >= 4) {
+			aligned_size = copy_size & ~3;
+			ret = esp_rom_flash_read(address, dest_ptr, aligned_size, allow_decrypt);
+			if (ret != ESP_OK) {
+				return -EIO;
+			}
+
+			address += aligned_size;
+			dest_ptr += aligned_size;
+			remaining -= aligned_size;
+		} else {
+			size_t start_addr = address - addr_offset;
 
+			aligned_size = (copy_size + addr_offset + 3) & ~3;
+
+			ret = esp_rom_flash_read(start_addr, temp_buf, aligned_size, allow_decrypt);
+			if (ret != ESP_OK) {
+				return -EIO;
+			}
+
+			memcpy(dest_ptr, temp_buf + addr_offset, copy_size);
+
+			address += copy_size;
+			dest_ptr += copy_size;
+			remaining -= copy_size;
+		}
+	}
+#else
 	flash_esp32_sem_take(dev);
 
 	if (esp_flash_encryption_enabled()) {
@@ -105,7 +146,6 @@ static int flash_esp32_read(const struct device *dev, off_t address, void *buffe
 	}
 
 	flash_esp32_sem_give(dev);
-
 #endif
 
 	if (ret != 0) {
@@ -124,21 +164,15 @@ static int flash_esp32_write(const struct device *dev,
 	int ret = 0;
 
 #ifdef CONFIG_MCUBOOT
-	/* ensure everything is 4-byte aligned */
-	size_t aligned_length = ROUND_UP(length, 4);
-	off_t aligned_address = ROUND_DOWN(address, 4);
-	size_t address_offset = address - aligned_address;
-	uint32_t temp_buf[aligned_length / 4];
-
-	if (!esp_flash_encryption_enabled()) {
-		ret = esp_rom_flash_write(aligned_address, temp_buf, aligned_length, false);
-	} else {
-		ret = esp_rom_flash_write(aligned_address, temp_buf, aligned_length, true);
+	if (!flash_esp32_is_aligned(address, (void *)buffer, length)) {
+		LOG_ERR("Unaligned flash write is not supported");
+		return -EINVAL;
 	}
 
-	memcpy((void *)buffer, ((uint8_t *)temp_buf) + address_offset, length);
-#else
+	bool encrypt = esp_flash_encryption_enabled();
 
+	ret = esp_rom_flash_write(address, (void *)buffer, length, encrypt);
+#else
 	flash_esp32_sem_take(dev);
 
 	if (esp_flash_encryption_enabled()) {
@@ -148,7 +182,6 @@ static int flash_esp32_write(const struct device *dev,
 	}
 
 	flash_esp32_sem_give(dev);
-
 #endif
 
 	if (ret != 0) {