RE: [PATCH V3 2/2] drivers/irqchip: add NXP INTMUX interrupt multiplexer support

[Joakim Zhang]

> -----Original Message-----
> From: Joakim Zhang
> Sent: 2019å12æ20æ 23:26
> To: 'Marc Zyngier' <maz@xxxxxxxxxx>
> Cc: Lokesh Vutla <lokeshvutla@xxxxxx>; tglx@xxxxxxxxxxxxx;
> jason@xxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx;
> shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; Andy Duan
> <fugang.duan@xxxxxxx>; S.j. Wang <shengjiu.wang@xxxxxxx>;
> linux-kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>;
> kernel@xxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [PATCH V3 2/2] drivers/irqchip: add NXP INTMUX interrupt
> multiplexer support
> 
> 
> > -----Original Message-----
> > From: Marc Zyngier <maz@xxxxxxxxxx>
> > Sent: 2019å12æ20æ 22:20
> > To: Joakim Zhang <qiangqing.zhang@xxxxxxx>
> > Cc: Lokesh Vutla <lokeshvutla@xxxxxx>; tglx@xxxxxxxxxxxxx;
> > jason@xxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx;
> > shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; Andy Duan
> > <fugang.duan@xxxxxxx>; S.j. Wang <shengjiu.wang@xxxxxxx>;
> > linux-kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>;
> > kernel@xxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Subject: RE: [PATCH V3 2/2] drivers/irqchip: add NXP INTMUX interrupt
> > multiplexer support
> >
> > On 2019-12-20 14:10, Joakim Zhang wrote:
> > >> -----Original Message-----
> > >> From: Lokesh Vutla <lokeshvutla@xxxxxx>
> >
> > [...]
> >
> > >> Does the user care to which channel does the interrupt source goes
> > >> to? If not, interrupt-cells in DT can just be a single entry and
> > >> the channel selection can be controlled by the driver no? I am
> > >> trying to understand why user should specify the channel no.
> > > Hi Lokesh,
> > >
> > > If a fixed channel is specified in the driver, all interrupt sources
> > > will be connected to this channel, affecting the interrupt priority
> > > to some extent.
> > >
> > > From my point of view, a fixed channel could be enough if don't care
> > > interrupt priority.
> >
> > Hold on a sec:
> >
> > Is the channel to which an interrupt is routed to programmable? What
> > has the priority of the interrupt to do with this? How does this
> > affect interrupt delivery?
> >
> > It looks like this HW does more that you initially explained...
> Hi Marc,
> 
> The channel to which an interrupt is routed to is not programmable. Each
> channel has the same 32 interrupt sources.
> Each channel has mask, unmask and status register.
> If use 1 channel, 32 interrupt sources input and 1 interrupt output.
> If use 2 channels, 32 interrupt sources input and 2 interrupts output.
> And so on. You can see above INTMUX block diagram. This is how HW works.
> 
> For example:
> 1) use 1 channel:
> We can enable 0~31 interrupt in channel 0. And 1 interrupt output. If generate
> interrupt, we cannot figure out which half happened first.
> 2)use 2 channels:
> We can enable 0~15 interrupt in channel 0, and enable 16~31 in channel 1.
> And 2 interrupts output. If generate interrupt, at least we can find channel 0 or
> channel 1 first. Then find 0~15 or 16~31 first.
> 
> This is my understanding of the interrupt priority from this intmux, I don't
> know if it is my misunderstanding.

So assign interrupt sources to multi-channels will generate multi-interrupt output. And these output interrupts are sequential. Could this be interpreted as interrupt priority?

Best Regards,
Joakim Zhang
> Best Regards,
> Joakim Zhang
> >          M.
> > --
> > Jazz is not dead. It just smells funny...