Messages in this thread | | | Date | Tue, 14 Jul 2015 13:48:25 +0200 | From | Noralf Trønnes <> | Subject | Re: [PATCH] irqchip: bcm2835: Add FIQ support |
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Den 14.07.2015 06:50, skrev Stephen Warren: > On 07/11/2015 09:26 AM, Noralf Trønnes wrote: >> Den 11.07.2015 06:09, skrev Stephen Warren: >>> (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. >> Yes, but doesn't this apply to all irq use, using the wrong one doesn't >> work. >> If FIQ's where in more common use, we might have seen a FIQ IRQ flag >> instead >> of special FIQ irqs. >> >>> (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. >> armctrl_xlate() maps to the same hwirqs as before. This patch adds a >> new range of hwirqs at the end of the "real" hwirq range. >> It's not possible to get to these FIQ shadow hwirqs through DT. > What prevents a DT from (incorrectly) referencing the extra hwirqs?
armctrl_xlate() has these limits:
if (WARN_ON(intspec[0] >= NR_BANKS)) if (WARN_ON(intspec[1] >= IRQS_PER_BANK)) if (WARN_ON(intspec[0] == 0 && intspec[1] >= NR_IRQS_BANK0))
Thus the maximum values allowed are: intspec[0]: (NR_BANKS - 1) = 2 intspec[1]: (IRQS_PER_BANK - 1) = 31
This gives a maximum hwirq: *out_hwirq = MAKE_HWIRQ(intspec[0], intspec[1]); *out_hwirq = (2 << 5) | 31 = 95
The FIQ shadow hwirq range starts at 96: irq = irq_create_mapping(intc.domain, MAKE_HWIRQ(b, i) + NUMBER_IRQS);
NUMBER_IRQS = MAKE_HWIRQ(NR_BANKS, 0) = 96
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