Re: [PATCH v7 2/4] CMDQ: Mediatek CMDQ driver

CK Hu
2016-05-26T07:28:38Z

Hi, HS:

Replay inline.

On Tue, 2016-05-24 at 20:27 +0800, Horng-Shyang Liao wrote:
> Hi CK,
>
> Reply in line.
>
> On Tue, 2016-05-24 at 11:05 +0800, CK Hu wrote:
> > Hi, HS:
> >
> > Some comments below.
> >
> ...
> > > +static void cmdq_thread_irq_handler(struct cmdq *cmdq, int tid)
> > > +{
> > > + struct cmdq_thread *thread = &cmdq->thread[tid];
> > > + unsigned long flags = 0L;
> > > + int value;
> > > +
> > > + spin_lock_irqsave(&cmdq->exec_lock, flags);
> > > +
> > > + /*
> > > + * it is possible for another CPU core
> > > + * to run "release task" right before we acquire the spin lock
> > > + * and thus reset / disable this HW thread
> > > + * so we check both the IRQ flag and the enable bit of this thread
> > > + */
> > > + value = cmdq_thread_readl(thread, CMDQ_THR_IRQ_STATUS);
> > > + if (!(value & CMDQ_THR_IRQ_MASK)) {
> > > + spin_unlock_irqrestore(&cmdq->exec_lock, flags);
> > > + return;
> > > + }
> >
> > If this case happen and just return without clearing irq status, the irq
> > would keep triggering and system hang up. So just remove this checking
> > and go down to clear irq status.
>
> This case is safe because irq status is cleared.
> But, next if condition has the problem which you mentioned.
>
> I will change it as below.
>
> if (!(cmdq_thread_readl(thread, CMDQ_THR_ENABLE_TASK) &
> CMDQ_THR_ENABLED)) {
> cmdq_thread_writel(thread, ~value, CMDQ_THR_IRQ_STATUS);
> spin_unlock_irqrestore(&cmdq->exec_lock, flags);
> return;
> }
>
> If thread is disabled, tasks must be all finished.
> Therefore, just clear irq status and return.
>

For irq status checking part, if irq status & irq mask is zero, remove
this checking and let it go down, it still do nothing because value &
CMDQ_THR_IRQ_ERROR is zero and value & CMDQ_THR_IRQ_DONE is zero. So you
can just remove this checking and get the same result.

In general HW design, once a HW is not enable, it does not trigger
interrupt any more. Be sure that it's necessary to clear irq status even
though thread is disable.

> > > +
> > > + if (!(cmdq_thread_readl(thread, CMDQ_THR_ENABLE_TASK) &
> > > + CMDQ_THR_ENABLED)) {
> > > + spin_unlock_irqrestore(&cmdq->exec_lock, flags);
> > > + return;
> > > + }
> > > +
> > > + cmdq_thread_writel(thread, ~value, CMDQ_THR_IRQ_STATUS);
> > > +
> > > + if (value & CMDQ_THR_IRQ_ERROR)
> > > + cmdq_handle_error_done(cmdq, thread, true);
> > > + else if (value & CMDQ_THR_IRQ_DONE)
> > > + cmdq_handle_error_done(cmdq, thread, false);
> >
> > These irq status checking and clearing code here is the same as those in
> > cmdq_task_handle_error_result(). To move the checking and clearing code
> > into cmdq_handle_error_done() and here just to call
> > cmdq_handle_error_done(cmdq, thread) would reduce duplicated code.
>
> Will do.
>
> > > +
> > > + spin_unlock_irqrestore(&cmdq->exec_lock, flags);
> > > +}
> ...
> ...
> >
> > Regards,
> > CK
>
> Thanks,
> HS
>

Regards,
CK