Messages in this thread | | | Date | Fri, 10 Jul 2015 22:09:52 -0600 | From | Stephen Warren <> | Subject | Re: [PATCH] irqchip: bcm2835: Add FIQ support |
| |
(Sorry for the slow reply; I was on vacation)
On 06/18/2015 07:32 AM, Noralf Trønnes wrote: > Den 18.06.2015 04:26, skrev Stephen Warren: >> On 06/12/2015 11:26 AM, Noralf Trønnes wrote: >>> Add a duplicate irq range with an offset on the hwirq's so the >>> driver can detect that enable_fiq() is used. >>> Tested with downstream dwc_otg USB controller driver. >> This basically looks OK, but a few comments/thoughts:
>> b) Doesn't the driver need to refuse some operation (handler >> registration, IRQ setup, IRQ enable, ...?) for more than 1 IRQ in the >> FIQ range, since the FIQ control register only allows routing 1 IRQ to >> FIQ. > > claim_fiq() protects the FIQ. See d) answer below.
That assumes the IRQ is "accessed" via the fiq-specific APIs. Since this patch changes the IRQ domain from having n IRQs to having 2*n IRQs, and doesn't do anything special to prevent clients from using IRQs n..2n-1 via the existing IRQ APIs, it's quite possible the a buggy client would.
(From another email): >>> c) The DT binding needs updating to describe the extra IRQs: >>> >>>> Documentation/devicetree/bindings/interrupt-controller/brcm,bcm28armctrl-ic.txt >> >> Ok. > > I have seconds thoughts on this: > This patch does not change the DT bindings so I don't see what update > I should make. This patch only adds support for the Linux way of > handling FIQ's through enable_fiq(). It doesn't change how interrupts > are described in the DT.
The intention of the patch may not be to expand the set of IRQs available via DT, but it does in practice. I think you need to add a custom of_xlate for the IRQ domain to ensure that only IRQs 0..n-1 can be translated from DT, and not IRQs n..2n-1. If you do that, then I agree that no DT binding update should be required.
Even with a custom of_xlate function, some code could hard-code an IRQ number and hence end up registering a FIQ handler that way. However, I guess that's a bug that the driver doesn't need to solve. We can just fix that bug in the kernel code in that case. The same argument doesn't apply to bad DTs; we need to more aggressively protect against that case.
>> d) I wonder how the FIQ handler actually gets routed to this controller >> and hooked to its handler etc. I assume there's a separate patch for >> that coming? > > set_fiq_handler() sets the handler and enable_fiq() enables it: > > if (claim_fiq(&fh)) > ERROR; > set_fiq_handler(...) > set_fiq_regs(®s); > enable_fiq(irq); > local_fiq_enable();
| |