[U-Boot] [PATCH v2] env: add spi_flash_read_env function

[Horatiu Vultur]

The spi_flash_read_env function is a wrapper over spi_flash_read, which
enables the env to read multiple flash page size from flash until '\0\0'
is read or the end of env partition is reached. Instead of reading the
entire env size. When it reads '\0\0', it stops reading further the env
and assumes that the rest of env is '\0'.

This is an optimization for large environments that contain few bytes
environment variables. In this case it doesn't need to read the entire
environment and only few pages.

Signed-off-by: Horatiu Vultur <horatiu.vultur at microchip.com>
---
 env/sf.c | 56 +++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 45 insertions(+), 11 deletions(-)

Changes in v2:
- rename flash_read to spi_flash_read_env
- change signature of is_end, by adding const to addr

diff --git a/env/sf.c b/env/sf.c
index 2e3c600..01fadee 100644
--- a/env/sf.c
+++ b/env/sf.c
@@ -81,6 +81,40 @@ static int setup_flash_device(void)
 	return 0;
 }
 
+static int is_end(const char *addr, size_t size)
+{
+	/* The end of env variables is marked by '\0\0' */
+	int i = 0;
+
+	for (i = 0; i < size - 1; ++i)
+		if (addr[i] == 0x0 && addr[i + 1] == 0x0)
+			return 1;
+	return 0;
+}
+
+static int spi_flash_read_env(struct spi_flash *flash, u32 offset, size_t len,
+			      void *buf)
+{
+	u32 addr = 0;
+	u32 page_size = flash->page_size;
+
+	memset(buf, 0x0, len);
+	for (int i = 0; i < len / page_size; ++i) {
+		int ret = spi_flash_read(flash, offset, page_size,
+					 &((char *)buf)[addr]);
+
+		if (ret < 0)
+			return ret;
+
+		if (is_end(&((char *)buf)[addr], page_size))
+			return 0;
+
+		addr += page_size;
+		offset += page_size;
+	}
+	return 0;
+}
+
 #if defined(CONFIG_ENV_OFFSET_REDUND)
 #ifdef CMD_SAVEENV
 static int env_sf_save(void)
@@ -116,8 +150,8 @@ static int env_sf_save(void)
 			ret = -ENOMEM;
 			goto done;
 		}
-		ret = spi_flash_read(env_flash, saved_offset,
-					saved_size, saved_buffer);
+		ret = spi_flash_read_env(env_flash, saved_offset,
+					 saved_size, saved_buffer);
 		if (ret)
 			goto done;
 	}
@@ -183,10 +217,10 @@ static int env_sf_load(void)
 	if (ret)
 		goto out;
 
-	read1_fail = spi_flash_read(env_flash, CONFIG_ENV_OFFSET,
-				    CONFIG_ENV_SIZE, tmp_env1);
-	read2_fail = spi_flash_read(env_flash, CONFIG_ENV_OFFSET_REDUND,
-				    CONFIG_ENV_SIZE, tmp_env2);
+	read1_fail = spi_flash_read_env(env_flash, CONFIG_ENV_OFFSET,
+					CONFIG_ENV_SIZE, tmp_env1);
+	read2_fail = spi_flash_read_env(env_flash, CONFIG_ENV_OFFSET_REDUND,
+					CONFIG_ENV_SIZE, tmp_env2);
 
 	ret = env_import_redund((char *)tmp_env1, read1_fail, (char *)tmp_env2,
 				read2_fail);
@@ -220,8 +254,8 @@ static int env_sf_save(void)
 		if (!saved_buffer)
 			goto done;
 
-		ret = spi_flash_read(env_flash, saved_offset,
-			saved_size, saved_buffer);
+		ret = spi_flash_read_env(env_flash, saved_offset,
+					 saved_size, saved_buffer);
 		if (ret)
 			goto done;
 	}
@@ -277,10 +311,10 @@ static int env_sf_load(void)
 	if (ret)
 		goto out;
 
-	ret = spi_flash_read(env_flash,
-		CONFIG_ENV_OFFSET, CONFIG_ENV_SIZE, buf);
+	ret = spi_flash_read_env(env_flash, CONFIG_ENV_OFFSET, CONFIG_ENV_SIZE,
+				 buf);
 	if (ret) {
-		set_default_env("spi_flash_read() failed", 0);
+		set_default_env("spi_flash_read_env() failed", 0);
 		goto err_read;
 	}
 
-- 
2.7.4