linux-kernel - Re: [PATCH 2/3] ARM: dts: bcm2711: Update SPI nodes compatible strings

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Message-ID: <20200604112112.b3k4wrftckndscu6@wunner.de>
Date:   Thu, 4 Jun 2020 13:21:12 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        "maintainer:BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITE..." 
        <bcm-kernel-feedback-list@...adcom.com>,
        "open list:SPI SUBSYSTEM" <linux-spi@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Martin Sperl <kernel@...tin.sperl.org>
Subject: Re: [PATCH 2/3] ARM: dts: bcm2711: Update SPI nodes compatible
 strings

On Thu, Jun 04, 2020 at 12:13:25PM +0100, Mark Brown wrote:
> On Thu, Jun 04, 2020 at 06:20:38AM +0200, Lukas Wunner wrote:
> > On Wed, Jun 03, 2020 at 08:46:54PM -0700, Florian Fainelli wrote:
> > > The BCM2711 SoC features 5 SPI controllers which all share the same
> > > interrupt line, the SPI driver needs to support interrupt sharing,
> > > therefore use the chip specific compatible string to help with that.
> 
> > You're saying above that the 5 controllers all share the interrupt
> > but below you're only changing the compatible string of 4 controllers.
> 
> > So I assume spi0 still has its own interrupt and only the additional
> > 4 controllers present on the BCM2711/BCM7211 share their interrupt?
> 
> Regardless of what's going on with the interrupts the compatible string
> should reflect the IP version so unless for some reason someone taped
> out two different versions of the IP it seems odd that the compatible
> strings would vary within a given SoC.

Hm.  I guess it may be possible to search the DT for other devices
sharing the same interrupt line and thereby determine whether
IRQF_SHARED is necessary.  The helper to perform this search could
live in drivers/of/irq.c as I imagine it might be useful in general.