On 2017-01-16 20:46, Jan Kiszka wrote:
> On 2017-01-16 20:07, Andy Shevchenko wrote:
>> On Mon, 2017-01-16 at 19:44 +0100, Jan Kiszka wrote:
>>> When using the a device with edge-triggered interrupts, such as MSIs,
>>> the interrupt handler has to ensure that there is a point in time
>>> during
>>> its execution where all interrupts sources are silent so that a new
>>> event can trigger a new interrupt again.
>>>
>>> This is achieved here by looping over SSSR evaluation. We need to take
>>> into account that SSCR1 may be changed by the transfer handler, thus
>>> we
>>> need to redo the mask calculation, at least regarding the volatile
>>> interrupt enable bit (TIE).
>>>
>>
>> So, more comments/questions below.
>>
>>>
>>> sccr1_reg = pxa2xx_spi_read(drv_data, SSCR1);
>>>
>>> - /* Ignore possible writes if we don't need to write */
>>> - if (!(sccr1_reg & SSCR1_TIE))
>>> - mask &= ~SSSR_TFS;
>>> -
>>> /* Ignore RX timeout interrupt if it is disabled */
>>> if (!(sccr1_reg & SSCR1_TINTE))
>>> mask &= ~SSSR_TINT;
>>>
>>> - if (!(status & mask))
>>> - return IRQ_NONE;
>>> + while (1) {
>>
>> Can we switch to do-while and move previous block here?
>
> Don't see how this would help (without duplicating more code).
>
>> Btw, can TINTE
>> bit be set again during a loop?
>
> Nope, it's statically set, at least so far.
>
> What we could do is simply restarting ssp_int
>
>>
>>> + /* Ignore possible writes if we don't need to write
>>> */
>>> + if (!(sccr1_reg & SSCR1_TIE))
>>> + mask &= ~SSSR_TFS;
>>>
>>> - if (!drv_data->master->cur_msg) {
>>> - handle_bad_msg(drv_data);
>>> - /* Never fail */
>>> - return IRQ_HANDLED;
>>> - }
>>> + if (!(status & mask))
>>> + return ret;
>>> +
>>> + if (!drv_data->master->cur_msg) {
>>> + handle_bad_msg(drv_data);
>>> + /* Never fail */
>>> + return IRQ_HANDLED;
>>> + }
>>> +
>>
>>> + ret |= drv_data->transfer_handler(drv_data);
>>
>> So, we might call handler several times. This needs to be commented in
>> the code why you do so.
>
> I can move the commit log into the code.
>
>>
>>>
>>> - return drv_data->transfer_handler(drv_data);
>>> + status = pxa2xx_spi_read(drv_data, SSSR);
>>
>> Would it be possible to get all 1:s from the register
>> (something/autosuspend just powered off it by timeout?) ?
>>
>
> Not sure if that can happen, but I guess it would be simpler and more
> readable to simply do this instead:
>
> while (1) {
> /*
> * If the device is not yet in RPM suspended state and we get an
> * interrupt that is meant for another device, check if status
> * bits are all set to one. That means that the device is
> * already powered off.
> */
> status = pxa2xx_spi_read(drv_data, SSSR);
> if (status == ~0)
> return ret;
>
> sccr1_reg = pxa2xx_spi_read(drv_data, SSCR1);
>
> /* Ignore RX timeout interrupt if it is disabled */
> if (!(sccr1_reg & SSCR1_TINTE))
> mask &= ~SSSR_TINT;
>
> /* Ignore possible writes if we don't need to write */
> if (!(sccr1_reg & SSCR1_TIE))
> mask &= ~SSSR_TFS;
>
> if (!(status & mask))
> return ret;
>
> if (!drv_data->master->cur_msg) {
> handle_bad_msg(drv_data);
> /* Never fail */
> return IRQ_HANDLED;
> }
>
> ret |= drv_data->transfer_handler(drv_data);
> }
>
>
> i.e. preserve the current structure, just add the loop.
>
OK, please let me know if you want a v3 of this patch with the structure
above. If there are further concerns/questions, just let me know as
well, but I'd like to close this topic if possible.
Thanks,
Jan
--
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux
