Re: [PATCH 1/3] spi: spi-mem: add automatic poll status functions

From: Patrice CHOTARD
Date: Fri Apr 30 2021 - 10:23:16 EST

Hi Mark, Pratyush

On 4/26/21 6:51 PM, Mark Brown wrote:
> On Mon, Apr 26, 2021 at 09:56:12PM +0530, Pratyush Yadav wrote:
>> On 26/04/21 04:39PM, patrice.chotard@xxxxxxxxxxx wrote:
>>> + * spi_mem_poll_status() - Poll memory device status
>>> + * @mem: SPI memory device
>>> + * @op: the memory operation to execute
>>> + * @mask: status bitmask to ckeck
>>> + * @match: status expected value
>> Technically, (status & mask) expected value. Dunno if that is obvious
>> enough to not spell out explicitly.
> Is it possible there's some situation where you're waiting for some bits
> to clear as well?
Yes, we are waiting STATUS_BUSY bit to be cleared, see patch 2 which is making
usage of this API.

>>> + ret = ctlr->mem_ops->poll_status(mem, op, mask, match, timeout);
> I'm not sure I like this name since it makes me think the driver is
> going to poll when really it's offloaded to the hardware, but I can't
> think of any better ideas either and it *is* what the hardware is going
> to be doing so meh.
>> I wonder if it is better to let spi-mem core take care of the timeout
>> part. On one hand it reduces code duplication on the driver side a
>> little bit. Plus it makes sure drivers don't mess anything up with bad
>> (or no) handling of the timeout. But on the other hand the interface
>> becomes a bit awkward since you'd have to pass a struct completion
>> around, and it isn't something particularly hard to get right either.
>> What do you think?
> We already have the core handling other timeouts. We don't pass around
> completions but rather have an API function that the driver has to call
> when the operation completes, a similar pattern might work here. Part

So, if i correctly understood, you make allusion to what is already done
in SPI core framework with spi_finalize_current_transfer() right ?

> of the thing with those APIs which I'm missing here is that this will
> just return -EOPNOTSUPP if the driver can't do the delay in hardware, I
> think it would be cleaner if this API were similar and the core dealt
> with doing the delay/poll on the CPU. That way the users don't need to
> repeat the handling for the offload/non-offload cases.

Sorry, i didn't catch what you mean here. In PATCH 2, that's the case,
if spi_mem_poll_status() is not supported, the core is dealing with
the delay/poll on the CPU in spinand_wait().