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.
Jan
--
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux
