Re: [U-Boot] [PATCH v3 1/9] sf: Update SST flash params

21 Apr 2015

      Hi Bin,
On 20 April 2015 at 15:02, Bin Meng bmeng.cn@gmail.com wrote:
...
Hi Jagan,
On Fri, Apr 17, 2015 at 4:48 PM, Jagan Teki jagannadh.teki@gmail.com wrote:
...
Hi Bin,
On 17 April 2015 at 07:14, Bin Meng bmeng.cn@gmail.com wrote:
...
Hi Jagan,
On Fri, Apr 17, 2015 at 2:09 AM, Jagan Teki jagannadh.teki@gmail.com wrote:
...
Hi Bin,
I think you have a different interpretation of sector size here-
/* The size listed here is what works with SPINOR_OP_SE, which isn't

necessarily called a "sector" by the vendor.

*/
Say for example SST25VF040B has 8 sectors of which each sector size is
64 * 1024 out of this we can use 4K sector erase or 32K sector erase or
64K sector erase through flags.
Linux does follow the same-
        /* SST -- large erase sizes are "overlays", "sectors" are 4K */
        { "sst25vf040b", INFO(0xbf258d, 0, 64 * 1024,  8, SECT_4K |
SST_WRITE) },
        { "sst25vf080b", INFO(0xbf258e, 0, 64 * 1024, 16, SECT_4K |
SST_WRITE) },
        { "sst25vf016b", INFO(0xbf2541, 0, 64 * 1024, 32, SECT_4K |
SST_WRITE) },
        { "sst25vf032b", INFO(0xbf254a, 0, 64 * 1024, 64, SECT_4K |
SST_WRITE) },
Please check it.
Yes, I know this pretty well. And I want to change this behavior, as
my cover letter says.
Currently the 'sf erase' command operates on a 64KB granularity, while
the actual erase command is 4KB granularity, which is inconsistent and
causes confusion.
It never related to 'sf erase' instead based on the 'params->flags'
sf_probe will decide which erase_cmd with erase_size will use.
No, it is related. See cmd_sf.c:
I'm not getting your point- how could it erase use 64K sector size
instead of 4K.
Suppose the sector size is 4K
flash->sector_size = 0x1000
1.  erase 4K  len flash (it's total erase length)
# sf erase 0x0 0x1000
len_arg = simple_strtoul(arg, &ep, 16);
 gives - 0x1000
*len becomes 0x1000
2.  erase 4K+1 len flash
# sf erase 0x0 +0x1001
len_arg = simple_strtoul(arg, &ep, 16);
 gives - 0x1001
*len becomes 0x2000
All the way when it goes to sf_ops.c erase will take by means of
erase_size which is assigned in sf_probe.c based on flags like 4K
32K or 64K.
...
static int sf_parse_len_arg(char *arg, ulong *len)
{
    char *ep;
    char round_up_len; /* indicates if the "+length" form used */
    ulong len_arg;
round_up_len = 0;
if (*arg == '+') {
    round_up_len = 1;
    ++arg;
}

len_arg = simple_strtoul(arg, &ep, 16);
if (ep == arg || *ep != '\0')
    return -1;

if (round_up_len && flash->sector_size > 0)
    *len = ROUND(len_arg, flash->sector_size);
else
    *len = len_arg;

return 1;

}
So even you are passing 4KB in the flash params, the 'sf erase'
command WILL erase 64KB.
...
    /* Compute erase sector and command */
    if (params->flags & SECT_4K) {
            flash->erase_cmd = CMD_ERASE_4K;
            flash->erase_size = 4096 << flash->shift;
    } else if (params->flags & SECT_32K) {
            flash->erase_cmd = CMD_ERASE_32K;
            flash->erase_size = 32768 << flash->shift;
    } else {
            flash->erase_cmd = CMD_ERASE_64K;
            flash->erase_size = flash->sector_size;
    }

And to be honest, these flashes were tested with lowest ie 4KB so even if they
do support 64KB, we mentioned on 4KB on 'params->flags' as we tested
well with that
and it works consistently.
thanks!
-- 
Jagan.