linux-kernel - Re: [PATCH 3/4] dt-bindings: i2c-stm32: add SMBus Alert bindings

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Date:   Sat, 23 May 2020 12:36:01 +0200
From:   "wsa@...nel.org" <wsa@...nel.org>
To:     Rob Herring <robh@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Pierre Yves MORDRET <pierre-yves.mordret@...com>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Fabrice GASNIER <fabrice.gasnier@...com>
Subject: Re: [PATCH 3/4] dt-bindings: i2c-stm32: add SMBus Alert bindings


> > > +        st,smbus-alert:
> > > +          description: Enable the SMBus Alert feature
> > > +          $ref: /schemas/types.yaml#/definitions/flag
> > > +
> > 
> > We already have smbus_alert interrupt. Can't you just check for this in 
> > the slave nodes and enable if found?
> 
> My understanding reading the code (smbalert_probe within i2c-smbus.c, of_i2c_setup_smbus_alert called when
> registering an adapter within i2c-core-smbus.c) is that smbus_alert refers to an interrupt on the
> adapter side. That is an interrupt that would be triggered when the adapter is receiving an smbus_alert
> message.
> In our case (stm32f7), we do not have specific interrupt for that purpose. The interrupt triggered when
> an SMBUS Alert is received (by the adapter) is the same interrupt as for other reasons and we check
> within the irq handler within stm32f7 the reason before calling i2c_handle_smbus_alert if the status
> register indicated an SMBUS Alert.
> So my understanding is that we cannot rely on the mechanism of naming an interrupt smbus_alert.
> Did I misunderstood something ?

I just wonder what is bad about specifying the same interrupt twice in
the interrupt properties? You could then check in probe if "smbus_alert"
is populated and if it matches the main irq.


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