NOR/CFI: simplify bufferwsize computation

Review and simplify computation of bufferwsize.
Add comments about variables' meaning.

The same code is present 3 times in the file.
Current patch updates all the 3 instances.

Step 1)
  Replace "switch(bank->chip_width) {...}".
  Illegal values of bank->chip_width are already dropped.
  For legal values, the code is equivalent to:
        bufferwsize = buffersize / bank->chip_width;

Step 2)
  The above code replacement plus the following line:
        bufferwsize /= (bank->bus_width / bank->chip_width);
  is merged in a single formula:
        bufferwsize = (buffersize / bank->chip_width) /
                (bank->bus_width / bank->chip_width);
  and simplified as:
        bufferwsize = buffersize / bank->bus_width;

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>

diff --git a/src/flash/nor/cfi.c b/src/flash/nor/cfi.c
index ba2d9095f1ddc603882ea4fcf94c4a29128fb6fa..f2ea947ad3d61b32ae610c8d722650f6c5a57acd 100644 (file)
--- a/src/flash/nor/cfi.c
+++ b/src/flash/nor/cfi.c
@@ -1604,9 +1604,11 @@ static int cfi_intel_write_words(struct flash_bank *bank, uint8_t *word, uint32_
        struct target *target = bank->target;
 
        /* Calculate buffer size and boundary mask */
+       /* buffersize is (buffer size per chip) * (number of chips) */
+       /* bufferwsize is buffersize in words */
        uint32_t buffersize = (1UL << cfi_info->max_buf_write_size) * (bank->bus_width / bank->chip_width);
        uint32_t buffermask = buffersize-1;
-       uint32_t bufferwsize;
+       uint32_t bufferwsize = buffersize / bank->bus_width;
 
        /* Check for valid range */
        if (address & buffermask)
@@ -1615,18 +1617,6 @@ static int cfi_intel_write_words(struct flash_bank *bank, uint8_t *word, uint32_
                          bank->base, address, cfi_info->max_buf_write_size);
                return ERROR_FLASH_OPERATION_FAILED;
        }
-       switch (bank->chip_width)
-       {
-       case 4 : bufferwsize = buffersize / 4; break;
-       case 2 : bufferwsize = buffersize / 2; break;
-       case 1 : bufferwsize = buffersize; break;
-       default:
-               LOG_ERROR("Unsupported chip width %d", bank->chip_width);
-               return ERROR_FLASH_OPERATION_FAILED;
-       }
-
-       bufferwsize/=(bank->bus_width / bank->chip_width);
-
 
        /* Check for valid size */
        if (wordcount > bufferwsize)
@@ -1733,9 +1723,11 @@ static int cfi_spansion_write_words(struct flash_bank *bank, uint8_t *word, uint
        struct cfi_spansion_pri_ext *pri_ext = cfi_info->pri_ext;
 
        /* Calculate buffer size and boundary mask */
+       /* buffersize is (buffer size per chip) * (number of chips) */
+       /* bufferwsize is buffersize in words */
        uint32_t buffersize = (1UL << cfi_info->max_buf_write_size) * (bank->bus_width / bank->chip_width);
        uint32_t buffermask = buffersize-1;
-       uint32_t bufferwsize;
+       uint32_t bufferwsize = buffersize / bank->bus_width;
 
        /* Check for valid range */
        if (address & buffermask)
@@ -1743,17 +1735,6 @@ static int cfi_spansion_write_words(struct flash_bank *bank, uint8_t *word, uint
                LOG_ERROR("Write address at base 0x%" PRIx32 ", address %" PRIx32 " not aligned to 2^%d boundary", bank->base, address, cfi_info->max_buf_write_size);
                return ERROR_FLASH_OPERATION_FAILED;
        }
-       switch (bank->chip_width)
-       {
-       case 4 : bufferwsize = buffersize / 4; break;
-       case 2 : bufferwsize = buffersize / 2; break;
-       case 1 : bufferwsize = buffersize; break;
-       default:
-               LOG_ERROR("Unsupported chip width %d", bank->chip_width);
-               return ERROR_FLASH_OPERATION_FAILED;
-       }
-
-       bufferwsize/=(bank->bus_width / bank->chip_width);
 
        /* Check for valid size */
        if (wordcount > bufferwsize)
@@ -1950,22 +1931,12 @@ static int cfi_write(struct flash_bank *bank, uint8_t *buffer, uint32_t offset,
        {
                if (retval == ERROR_TARGET_RESOURCE_NOT_AVAILABLE)
                {
-                       //adjust buffersize for chip width
+                       /* Calculate buffer size and boundary mask */
+                       /* buffersize is (buffer size per chip) * (number of chips) */
+                       /* bufferwsize is buffersize in words */
                        uint32_t buffersize = (1UL << cfi_info->max_buf_write_size) * (bank->bus_width / bank->chip_width);
                        uint32_t buffermask = buffersize-1;
-                       uint32_t bufferwsize;
-
-                       switch (bank->chip_width)
-                       {
-                       case 4 : bufferwsize = buffersize / 4; break;
-                       case 2 : bufferwsize = buffersize / 2; break;
-                       case 1 : bufferwsize = buffersize; break;
-                       default:
-                               LOG_ERROR("Unsupported chip width %d", bank->chip_width);
-                               return ERROR_FLASH_OPERATION_FAILED;
-                       }
-
-                       bufferwsize/=(bank->bus_width / bank->chip_width);
+                       uint32_t bufferwsize = buffersize / bank->bus_width;
 
                        /* fall back to memory writes */
                        while (count >= (uint32_t)bank->bus_width)