On 24/06/2021 10:56, Boris Brezillon wrote:
> On Thu, 24 Jun 2021 10:23:51 +0100
> Steven Price <steven.pr...@arm.com> wrote:
>
>>> static void panfrost_job_handle_irq(struct panfrost_device *pfdev, u32
>>> status)
>>> {
>>> - int j;
>>> + struct panfrost_job *done[NUM_JOB_SLOTS][2] = {};
>>> + struct panfrost_job *failed[NUM_JOB_SLOTS] = {};
>>> + u32 js_state, js_events = 0;
>>> + unsigned int i, j;
>>>
>>> - dev_dbg(pfdev->dev, "jobslot irq status=%x\n", status);
>>> + while (status) {
>>> + for (j = 0; j < NUM_JOB_SLOTS; j++) {
>>> + if (status & JOB_INT_MASK_DONE(j)) {
>>> + if (done[j][0]) {
>>> + done[j][1] =
>>> panfrost_dequeue_job(pfdev, j);
>>> + WARN_ON(!done[j][1]);
>>> + } else {
>>> + done[j][0] =
>>> panfrost_dequeue_job(pfdev, j);
>>> + WARN_ON(!done[j][0]);
>>
>> NIT: I'd be tempted to move this WARN_ON into panfrost_dequeue_job() as
>> it's relevant for any call to the function.
>
> Makes sense. I'll move those WARN_ON()s.
>
>>
>>> + }
>>> + }
>>>
>>> - for (j = 0; status; j++) {
>>> - u32 mask = MK_JS_MASK(j);
>>> + if (status & JOB_INT_MASK_ERR(j)) {
>>> + /* Cancel the next submission. Will be submitted
>>> + * after we're done handling this failure if
>>> + * there's no reset pending.
>>> + */
>>> + job_write(pfdev, JS_COMMAND_NEXT(j),
>>> JS_COMMAND_NOP);
>>> + failed[j] = panfrost_dequeue_job(pfdev, j);
>>> + }
>>> + }
>>>
>>> - if (!(status & mask))
>>> + /* JS_STATE is sampled when JOB_INT_CLEAR is written.
>>> + * For each BIT(slot) or BIT(slot + 16) bit written to
>>> + * JOB_INT_CLEAR, the corresponding bits in JS_STATE
>>> + * (BIT(slot) and BIT(slot + 16)) are updated, but this
>>> + * is racy. If we only have one job done at the time we
>>> + * read JOB_INT_RAWSTAT but the second job fails before we
>>> + * clear the status, we end up with a status containing
>>> + * only the DONE bit and consider both jobs as DONE since
>>> + * JS_STATE reports both NEXT and CURRENT as inactive.
>>> + * To prevent that, let's repeat this clear+read steps
>>> + * until status is 0.
>>> + */
>>> + job_write(pfdev, JOB_INT_CLEAR, status);
>>> + js_state = job_read(pfdev, JOB_INT_JS_STATE);
>>
>> This seems a bit dodgy. The spec says that JOB_INT_JS_STATE[1] is
>> updated only for the job slots which have bits set in the JOB_INT_CLEAR.
>> So there's potentially two problems:
>>
>> * The spec makes no gaurentee about the values of the bits for other
>> slots. But we're not masking off those bits.
>>
>> * If we loop (e.g. because the other slot finishes while handling the
>> first interrupt) then we may lose the state for the first slot.
>>
>> I'm not sure what the actual hardware returns in the bits which are
>> unrelated to the previous JOB_INT_CLEAR - kbase is careful only to
>> consider the bits relating to the slot it's currently dealing with.
>
> Hm, I see. How about something like that?
>
> struct panfrost_job *done[NUM_JOB_SLOTS][2] = {};
> struct panfrost_job *failed[NUM_JOB_SLOTS] = {};
> u32 js_state = 0, js_events = 0;
> unsigned int i, j;
>
> while (status) {
> u32 js_state_mask = 0;
>
> for (j = 0; j < NUM_JOB_SLOTS; j++) {
> if (status & MK_JS_MASK(j))
> js_state_mask |= MK_JS_MASK(j);
>
> if (status & JOB_INT_MASK_DONE(j)) {
> if (done[j][0]) {
> done[j][1] =
> panfrost_dequeue_job(pfdev, j);
> WARN_ON(!done[j][1]);
> } else {
> done[j][0] =
> panfrost_dequeue_job(pfdev, j);
> WARN_ON(!done[j][0]);
> }
> }
>
> if (status & JOB_INT_MASK_ERR(j)) {
> /* Cancel the next submission. Will be
> submitted
> * after we're done handling this failure if
> * there's no reset pending.
> */
> job_write(pfdev, JS_COMMAND_NEXT(j),
> JS_COMMAND_NOP);
> failed[j] = panfrost_dequeue_job(pfdev, j);
> }
> }
>
> /* JS_STATE is sampled when JOB_INT_CLEAR is written.
> * For each BIT(slot) or BIT(slot + 16) bit written to
> * JOB_INT_CLEAR, the corresponding bits in JS_STATE
> * (BIT(slot) and BIT(slot + 16)) are updated, but this
> * is racy. If we only have one job done at the time we
> * read JOB_INT_RAWSTAT but the second job fails before we
> * clear the status, we end up with a status containing
> * only the DONE bit and consider both jobs as DONE since
> * JS_STATE reports both NEXT and CURRENT as inactive.
> * To prevent that, let's repeat this clear+read steps
> * until status is 0.
> */
> job_write(pfdev, JOB_INT_CLEAR, status);
> js_state &= ~js_state_mask;
> js_state |= job_read(pfdev, JOB_INT_JS_STATE) & js_state_mask;
> js_events |= status;
> status = job_read(pfdev, JOB_INT_RAWSTAT);
> }
>
That looks like it should work.
>>
>> [1] Actually JOB_IRQ_JS_STATE - I sometimes think we should rename to
>> match the spec, I keep searching the docs for the wrong name ;)
>
> I can add a patch doing that :-).
>
>>>
>>> - status &= ~mask;
>>> + for (j = 0; j < NUM_JOB_SLOTS; j++) {
>>> + if (!(js_events & MK_JS_MASK(j)))
>>> + continue;
>>> +
>>> + if (!failed[j] || !pfdev->jobs[j][0])
>>> + continue;
>>> +
>>> + if (pfdev->jobs[j][0]->jc == 0) {
>>> + /* The job was cancelled, signal the fence now */
>>> + struct panfrost_job *canceled =
>>> panfrost_dequeue_job(pfdev, j);
>>> +
>>> + panfrost_mmu_as_put(pfdev, canceled->file_priv->mmu);
>>> + panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
>>> +
>>> + dma_fence_set_error(canceled->done_fence, -ECANCELED);
>>> + dma_fence_signal_locked(canceled->done_fence);
>>> + pm_runtime_put_autosuspend(pfdev->dev);
>>> + } else if (!atomic_read(&pfdev->reset.pending)) {
>>> + /* Resume the job we stopped if no reset is pending */
>>> + job_write(pfdev, JS_COMMAND_NEXT(j), JS_COMMAND_START);
>>>
>>
>> If I'm following correctly this is resubmitting a soft-stopped job. But
>> I haven't seen where the new JC pointer is written.
>
> Not exactly. It's submitting a job that was queued but not started.
> When we see a fault, we write NOP to COMMAND_NEXT so the next job is
> not started when the interrupt is cleared. And here we're just
> requeuing it.
>
Ah that makes sense, then can you at least update the comment to not say
"stopped". Perhaps "removed" instead? I think that's what confused me.
Thanks,
Steve
