spi-nor: excessive locking in spi_nor_erase()

From: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
To: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>
Subject: spi-nor: excessive locking in spi_nor_erase()
Date: Mon, 15 Apr 2024 15:55:10 +0000	[thread overview]
Message-ID: <069251d381826e9bc8a59c49c39c393c2860a028.camel@infinera.com> (raw)

static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
{
...
Lock here
	ret = spi_nor_lock_and_prep(nor);
	if (ret)
		return ret;
....
Then we have:
	} else if (spi_nor_has_uniform_erase(nor)) {
		while (len) {
			ret = spi_nor_write_enable(nor);
			if (ret)
				goto erase_err;

			ret = spi_nor_erase_sector(nor, addr);
			if (ret)
				goto erase_err;

			ret = spi_nor_wait_till_ready(nor);
			if (ret)
				goto erase_err;

			addr += mtd->erasesize;
			len -= mtd->erasesize;
		}

	/* erase multiple sectors */
	} else {
		ret = spi_nor_erase_multi_sectors(nor, addr, len);
		if (ret)
			goto erase_err;
	}
....
erase_err:
unlock here
	spi_nor_unlock_and_unprep(nor);

	return ret;
}

So erase locks the flash for the whole erase op which can include many sectors and I don't see
any Erase Suspend handling in spi-nor like the cfi_cmdset_0001/cfi_cmdset_0002 has.

Locking can be a challenge but this seems over the top, anyone working/looking into improving this?

    Jocke
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