Re: [PATCH 1/3] spi: xilinx: Detect stall with Unknown commands

[Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx>]

Hi again

On Wed, Nov 22, 2017 at 8:25 PM, Ricardo Ribalda Delgado
<ricardo.ribalda@xxxxxxxxx> wrote:
> Hi Mark
>
>
> On Wed, Nov 22, 2017 at 12:12 PM, Mark Brown <broonie@xxxxxxxxxx> wrote:
>> On Tue, Nov 21, 2017 at 10:09:02AM +0100, Ricardo Ribalda Delgado wrote:
>>
>>> +             stalled = 10;
>>>               while (rx_words) {
>>> +                     if (rx_words == n_words && !(stalled--) &&
>>> +                         !(sr & XSPI_SR_TX_EMPTY_MASK) &&
>>> +                         (sr & XSPI_SR_RX_EMPTY_MASK)) {
>>
>> 10 seems like a small number for what is essentially just a busy spin -
>> are we sure that we won't reasonably hit a case where the CPU is
>> sufficiently fast and the bus sufficiently slow we falsely detect a
>> stall?  Where did this number come from?
>
> This code is executed after all the data has been pushed to the out
> fifo. Since we are not inhibitng tx, the moment the empty mask is
> evaluated,  at least one byte should be out.
>
> After 1 day of use I have been able to locate one event when stalled
> was two. So 10 is very conservative number.
>
> In other words: 10 is one order of magnitude bigger than the worst
> measured case.


If it makes you more comfortable I could add something like

if (n_tries < 8)
   msleep(10);

Regards!

>
> Thanks for your review :)
>
>
> --
> Ricardo Ribalda



-- 
Ricardo Ribalda
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