Dear Mike Frysinger,
In message 200812110431.35694.vapier@gentoo.org you wrote:
the different flash subsystems dont exactly all operate the same, specifically when it comes to erasing. some require you to specify lengths that are aligned exactly to the erase sector size whereas others are much more intelligent: they automatically round up for you. is there any real arguments for a particular method ?
Flash commands *should* support two formats:
1) sector (and bank) numbers, for example:
erase 1:3-6
2) start and end address, for example:
erase 40000000 4003FFFF
3) start address and length, for example:
erase 40000000 +40000
The idea is that addresses (start and end address) have to be exact and match sector boundaries as needed by the flash device, while length is handled intelligently, i. e. to erase one sector you can write
erase 40000000 +1
Sector and bank numbers have to be exact, too, of course.
personally, i prefer the latter behavior as it makes scripting a hell of a lot easier. for example, if i want to load a binary file into a flash, the loading process (i.e. tftp) will automatically set $(filesize) which i can then use as the erase/write length. otherwise i need to either manually do the rounding up based on sector size, or i have to assume ahead of time that the file will never exceed a certain max size and use that hardcoded value (which leads to wasted time erasing sectors that never actually get used and unable to use the same code across multiple platforms).
That's why the "+length" method was added.
here's an example change to the SPI flash driver: --- a/u-boot-2008.10/drivers/mtd/spi/stmicro.c +++ b/u-boot-2008.10/drivers/mtd/spi/stmicro.c @@ -262,12 +262,12 @@ int stmicro_erase(struct spi_flash
sector_size = stm->params->page_size * stm->params->pages_per_sector;
- if (offset % sector_size || len % sector_size) {
- if (offset % sector_size) { debug("SF: Erase offset/length not multiple of sector size\n"); return -1; }
- len /= sector_size;
- len = len / sector_size + !!(len % sector_size);
Except for the notation, which I find not so easy to read, that's OK with me. Is a documentation update needed?
Best regards,
Wolfgang Denk