Re: [spi-devel-general] [PATCH] SST25L (non JEDEC) SPI Flash driver

Ryan Mallon
2009-06-25T02:50:46Z

H Hartley Sweeten wrote:
> On Wednesday, June 24, 2009 7:06 PM, Ryan Mallon wrote:
>> H Hartley Sweeten wrote:
>>> On Sunday, June 21, 2009 8:59 PM, Ryan Mallon wrote:

> I think you could still support the block erase and chip erase internal
> to the driver for performance. Maybe something like the following?
>
> static int sst25l_erase(struct mtd_info *mtd, struct erase_info *instr)
> {
...
> if (instr->len == mtd->size) {
> err = __sst25l_erase(flash, addr, SST25L_CMD_CHIP_ERASE);
> if (err) {
> mutex_unlock(&flash->lock);
> instr->state = MTD_ERASE_FAILED;
> dev_err(&flash->spi->dev, "Erase failed\n");
> return err;
> }
> } else {
> while (addr < end) {
> u32 erasesize;
>
> if (addr % block || addr + block > end) {
> erasesize = sector;
> err = __sst25l_erase(flash, addr,
> SST25L_CMD_SECTOR_ERASE);
> } else {
> erasesize = block;
> err = __sst25l_erase(flash, addr,
> SST25L_CMD_BLOCK_ERASE);
> }
> if (err) {
> mutex_unlock(&flash->lock);
> instr->state = MTD_ERASE_FAILED;
> dev_err(&flash->spi->dev, "Erase failed\n");
> return err;
> }
>
> addr += erasesize;
> }
> }

>
> You would need to add sector_size and block_size to the ss25l_flash
> and flash_info structs and modify flash_info as appropriate. Then copy
> those over during the probe and use sector_size for mtd.erasesize.
>
> That way we get the 4K erase size but still get the performance increase
> for block and chip erase.

We discussed this, but it adds additional complexity to what is
otherwise quite a simple driver. The 4K sector erase will work in all
cases, and the speed difference shouldn't be a massive problem. I would
venture a guess that most people using the chips have reasonably
non-volatile storage on them, and don't get erased very often. We use
ours for the Bootloader and boot environment.

~Ryan

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