[PATCH u-boot-spi v3 09/10] mtd: mtdpart: Make mtdpart's _erase method sane

Marek Behún
2021-10-05T13:58:10Z

The _erase() method of the mtdpart driver, part_erase(), currently
implements offset shifting (for given mtdpart partition) in a weird way:
1. part_erase() adds partition offset to block address
2. parent driver's _erase() method is called
3. parent driver's _erase() method calls mtd_erase_callback()
4. mtd_erase_callback() subtracts partition offset from block address
so that the callback function is given correct address
The problem here is that if the parent's driver does not call
mtd_erase_callback() in some scenario (this was recently a case for
spi_nor_erase(), which did not call mtd_erase_callback() at all), the
offset is not shifted back.

Moreover the code would be more readable if part_erase() not only added
partition offset before calling parent's _erase(), but also subtracted
it back afterwards. Currently the mtd_erase_callback() is expected to do
this subtracting since it does have to do it anyway.

Add the more steps to this procedure:
5. mtd_erase_callback() adds partition offset to block address so that
it returns the the erase_info structure members as it received them
6. part_erase() subtracts partition offset from block address

This makes the code more logical and also prevents errors in case
parent's driver does not call mtd_erase_callback() for some reason.

(BTW, the purpose of mtd_erase_callback() in Linux is to inform the
caller that it is done, since in Linux erasing is done asynchronously.
We are abusing the purpose of mtd_erase_callback() in U-Boot for
completely different purpose. The callback function itself has empty
implementation in all cases in U-Boot.)

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>
---
drivers/mtd/mtdpart.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index aa58f722da..6ab481a7b1 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -446,24 +446,34 @@ static int part_erase(struct mtd_info *mtd, struct erase_info *instr)
int ret;

instr->addr += mtd->offset;
+
ret = mtd->parent->_erase(mtd->parent, instr);
- if (ret) {
- if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
- instr->fail_addr -= mtd->offset;
- instr->addr -= mtd->offset;
- }
+ if (ret && instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
+ instr->fail_addr -= mtd->offset;
+
+ instr->addr -= mtd->offset;
+
return ret;
}

void mtd_erase_callback(struct erase_info *instr)
{
- if (instr->mtd->_erase == part_erase) {
+ if (!instr->callback)
+ return;
+
+ if (instr->mtd->_erase == part_erase && instr->len) {
if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
instr->fail_addr -= instr->mtd->offset;
instr->addr -= instr->mtd->offset;
}
- if (instr->callback)
- instr->callback(instr);
+
+ instr->callback(instr);
+
+ if (instr->mtd->_erase == part_erase && instr->len) {
+ if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
+ instr->fail_addr += instr->mtd->offset;
+ instr->addr += instr->mtd->offset;
+ }
}
EXPORT_SYMBOL_GPL(mtd_erase_callback);

--
2.32.0