[PATCH 2/6] spi: sun4i: restrict transfer length in PIO-mode

[Sergey Suloev]

On 04/03/2018 11:10 AM, Maxime Ripard wrote:
> On Thu, Mar 29, 2018 at 09:59:03PM +0300, Sergey Suloev wrote:
>> There is no need to handle 3/4 empty/full interrupts as the maximum
>> supported transfer length in PIO mode is 64 bytes for sun4i-family
>> SoCs.
> That assumes that you'll be able to treat the FIFO full interrupt and
> drain the FIFO before we have the next byte coming in. This would
> require a real time system, and we're not in one of them.
>
> Maxime
>
AFAIK in SPI protocol we send and receive at the same time. As soon as 
the transfer length

is <= FIFO depth then it means that at the moment we get TC interrupt 
all data for this transfer

sent/received already.

Is your point here that draining FIFO might be a long operation and we 
can lose next portion of data ?