Re: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode

From: Sergey Suloev
Date: Fri Apr 06 2018 - 11:48:34 EST

On 04/06/2018 10:34 AM, Maxime Ripard wrote:
On Thu, Apr 05, 2018 at 04:44:16PM +0300, Sergey Suloev wrote:
On 04/05/2018 04:17 PM, Mark Brown wrote:
On Thu, Apr 05, 2018 at 12:59:35PM +0300, Sergey Suloev wrote:
On 04/05/2018 12:19 PM, Maxime Ripard wrote:
The point of that patch was precisely to allow to send more data than
the FIFO. You're breaking that behaviour without any justification,
and this is not ok.
I am sorry, but you can't. That's a hardware limitation.
Are you positive about that? Normally you can add things to hardware
FIFOs while they're being drained so so long as you can keep data
flowing in at least as fast as it's being consumed.
Well, normally yes, but this is not the case with the hardware that I own.
My a20 (BPiM1+) and a31 (BPiM2) boards behaves differently. With a transfer
larger than FIFO then TC interrupt never happens.
Because you're not supposed to have a transfer larger than the FIFO,
but to have to setup at first a transfer the size of the FIFO, and
then when it's (or starts to be) depleted, fill it up again.

According to what you said the driver must implement "transfer_one_message" instead of "transfer_one"

That's the point of the patch you're reverting, and if it doesn't
work, you should make it work and not simply revert it.