nand_get_device() was complex for apparently no good reason. Let's
replace this locking scheme with 2 mutexes: one attached to the
controller and another one attached to the chip.
Every time the core calls nand_get_device(), it will first lock the
chip and if the chip is not suspended, will then lock the controller.
nand_release_device() will release both lock in the reverse order.
nand_get_device() can sleep, just like the previous implementation,
which means you should never call that from an atomic context.
We also get rid of
- the chip->state field, since all it was used for was flagging the
chip as suspended. We replace it by a field called chip->suspended
and directly set it from nand_suspend/resume()
- the controller->wq and controller->active fields which are no longer
needed since the new controller->lock (now a mutex) guarantees that
all operations are serialized at the controller level
- panic_nand_get_device() which would anyway be a no-op. Talking about
panic write, I keep thinking the rawnand implementation is unsafe
because there's not negotiation with the controller to know when it's
actually done with it's previous operation. I don't intend to fix
that here, but that's probably something we should look at, or maybe
we should consider dropping the ->_panic_write() implementation
Last important change to mention: we now return -EBUSY when someone
tries to access a device that as been suspended, and propagate this
error to the upper layer.
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
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