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Subject: Re: [PATCH] wlcore/wl18xx: Add invert-irq OF property for physically
 inverted IRQ
To:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Tony Lindgren <tony@atomide.com>
Cc:     Kalle Valo <kvalo@codeaurora.org>,
        Eugeniu Rosca <erosca@de.adit-jv.com>,
        Simon Horman <horms+renesas@verge.net.au>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        John Stultz <john.stultz@linaro.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Spyridon Papageorgiou <spapageorgiou@de.adit-jv.com>,
        Joshua Frkuska <joshua_frkuska@mentor.com>,
        "George G . Davis" <george_davis@mentor.com>,
        Andrey Gusakov <andrey.gusakov@cogentembedded.com>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Eugeniu Rosca <roscaeugeniu@gmail.com>, eyalr@ti.com,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>
References: <20190607172958.20745-1-erosca@de.adit-jv.com>
 <87tvcxncuq.fsf@codeaurora.org> <20190610083012.GV5447@atomide.com>
 <CAMuHMdUOc17ocqmt=oNmyN1UT_K7_y=af1pwjwr5PTgQL2o2OQ@mail.gmail.com>
From:   Marc Zyngier <marc.zyngier@arm.com>
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Organization: ARM Ltd
Message-ID: <08bc4755-5f47-d792-8b5a-927b5fbe7619@arm.com>
Date:   Tue, 11 Jun 2019 10:00:41 +0100
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On 11/06/2019 09:45, Geert Uytterhoeven wrote:
> CC irqchip
> 
> Original thread at
> https://lore.kernel.org/lkml/20190607172958.20745-1-erosca@de.adit-jv.com/
> 
> On Mon, Jun 10, 2019 at 10:30 AM Tony Lindgren <tony@atomide.com> wrote:
>> * Kalle Valo <kvalo@codeaurora.org> [190610 07:01]:
>>> Eugeniu Rosca <erosca@de.adit-jv.com> writes:
>>>
>>>> The wl1837mod datasheet [1] says about the WL_IRQ pin:
>>>>
>>>>  ---8<---
>>>> SDIO available, interrupt out. Active high. [..]
>>>> Set to rising edge (active high) on powerup.
>>>>  ---8<---
>>>>
>>>> That's the reason of seeing the interrupt configured as:
>>>>  - IRQ_TYPE_EDGE_RISING on HiKey 960/970
>>>>  - IRQ_TYPE_LEVEL_HIGH on a number of i.MX6 platforms
>>>>
>>>> We assert that all those platforms have the WL_IRQ pin connected
>>>> to the SoC _directly_ (confirmed on HiKey 970 [2]).
>>>>
>>>> That's not the case for R-Car Kingfisher extension target, which carries
>>>> a WL1837MODGIMOCT IC. There is an SN74LV1T04DBVR inverter present
>>>> between the WLAN_IRQ pin of the WL18* chip and the SoC, effectively
>>>> reversing the requirement quoted from [1]. IOW, in Kingfisher DTS
>>>> configuration we would need to use IRQ_TYPE_EDGE_FALLING or
>>>> IRQ_TYPE_LEVEL_LOW.
>>>>
>>>> Unfortunately, v4.2-rc1 commit bd763482c82ea2 ("wl18xx: wlan_irq:
>>>> support platform dependent interrupt types") made a special case out
>>>> of these interrupt types. After this commit, it is impossible to provide
>>>> an IRQ configuration via DTS which would describe an inverter present
>>>> between the WL18* chip and the SoC, generating the need for workarounds
>>>> like [3].
>>>>
>>>> Create a boolean OF property, called "invert-irq" to specify that
>>>> the WLAN_IRQ pin of WL18* is connected to the SoC via an inverter.
>>>>
>>>> This solution has been successfully tested on R-Car H3ULCB-KF-M06 using
>>>> the DTS configuration [4] combined with the "invert-irq" property.
>>>>
>>>> [1] http://www.ti.com/lit/ds/symlink/wl1837mod.pdf
>>>> [2] https://www.96boards.org/documentation/consumer/hikey/hikey970/hardware-docs/
>>>> [3] https://github.com/CogentEmbedded/meta-rcar/blob/289fbd4f8354/meta-rcar-gen3-adas/recipes-kernel/linux/linux-renesas/0024-wl18xx-do-not-invert-IRQ-on-WLxxxx-side.patch
>>>> [4] https://patchwork.kernel.org/patch/10895879/
>>>>     ("arm64: dts: ulcb-kf: Add support for TI WL1837")
>>>>
>>>> Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
>>>
>>> Tony&Eyal, do you agree with this?
>>
>> Yeah if there's some hardware between the WLAN device and the SoC
>> inverting the interrupt, I don't think we have clear a way to deal
>> with it short of setting up a separate irqchip that does the
>> translation.
> 
> Yeah, inverting the interrupt type in DT works only for simple devices,
> that don't need configuration.
> A simple irqchip driver that just inverts the type sounds like a good
> solution to me. Does something like that already exists?

We already have plenty of that in the tree, the canonical example
probably being drivers/irqchip/irq-mtk-sysirq.c. It should be pretty
easy to turn this driver into something more generic.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...