[U-Boot] [PATCH v2 2/2] cmd_sf: "sf update" preserve the final part of the last sector

[Gerlando Falauto]

Hi,

On 07/03/2013 05:04 PM, Jagan Teki wrote:
> Hi,
>
> Thanks for the v2.
>
> On Fri, Jun 28, 2013 at 1:13 PM, Gerlando Falauto
> <gerlando.falauto at keymile.com> wrote:
>> Since "sf update" erases the last block as a whole, but only rewrites
>> the meaningful initial part of it, the rest would be left erased,
>> potentially erasing meaningful information.
>> So, as a safety measure, have it rewrite the original content.
>>
>> Signed-off-by: Gerlando Falauto <gerlando.falauto at keymile.com>
>> Cc: Valentin Longchamp <valentin.longchamp at keymile.com>
>> Cc: Holger Brunck <holger.brunck at keymile.com>
>> Acked-by: Simon Glass <sjg at chromium.org>
>> ---
>>   common/cmd_sf.c |   15 ++++++++++++++-
>>   1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/common/cmd_sf.c b/common/cmd_sf.c
>> index ab35a94..fb87d24 100644
>> --- a/common/cmd_sf.c
>> +++ b/common/cmd_sf.c
>> @@ -152,8 +152,10 @@ static const char *spi_flash_update_block(struct spi_flash *flash, u32 offset,
>>   {
>>          debug("offset=%#x, sector_size=%#x, len=%#zx\n",
>>                  offset, flash->sector_size, len);
>> -       if (spi_flash_read(flash, offset, len, cmp_buf))
>> +       /* Read the entire sector so to allow for rewriting */
>> +       if (spi_flash_read(flash, offset, flash->sector_size, cmp_buf))
>>                  return "read";
>> +       /* Compare only what is meningful (len) */
>>          if (memcmp(cmp_buf, buf, len) == 0) {
>>                  debug("Skip region %x size %zx: no change\n",
>>                          offset, len);
>> @@ -163,6 +165,17 @@ static const char *spi_flash_update_block(struct spi_flash *flash, u32 offset,
>>          /* Erase the entire sector */
>>          if (spi_flash_erase(flash, offset, flash->sector_size))
>>                  return "erase";
>> +       /* If it's a partial sector, preserve the existing part */
>> +       if (len != flash->sector_size) {
>> +               /* Overwrite the first part of the sector with input data */
>> +               memcpy(cmp_buf, buf, len);
>
> Can comment about memcpy() here, as Simon is also asked in v1
> http://patchwork.ozlabs.org/patch/150468/

Whoops, sorry!
I most probably did not see the comment (stopped reading at the Acked-By 
line) the first time around and *DEFINITELY* did not see it before 
posting v2.

I now understand your point, Simon.
This would imply two spi_flash_write() operations as opposed to just 
one, yet allowing for cleaner code.
I guess I was originally trying to both preserve the original behavior 
(always write whole sectors) and save on the number of write operations.
But that does not make much sense as we're speaking of an SPI NOR flash 
here, the only penalty from an extra write operation only comes from the 
extra SPI command. Not really much.

I'll post a v3 soon.

My apologies again.

Thanks,
Gerlando

>
> --
> Thanks,
> Jagan.
>
>> +               /* Rewrite the whole sector with original data at the end */
>> +               if (spi_flash_write(flash, offset, flash->sector_size,
>> +                                       cmp_buf))
>> +                       return "write";
>> +               return NULL;
>> +       }
>> +       /* Rewrite the whole block from the source */
>>          if (spi_flash_write(flash, offset, len, buf))
>>                  return "write";
>>          return NULL;
>> --
>> 1.7.10.1
>>