linux-kernel - RE: [LINUX PATCH v2 1/3] clocksource: timer-cadence-ttc: Do not probe TTC device configured as PWM

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Date:   Fri, 24 Nov 2023 11:03:24 +0000
From:   "Sayyed, Mubin" <mubin.sayyed@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "git (AMD-Xilinx)" <git@....com>,
        "mubin10@...il.com" <mubin10@...il.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "Simek, Michal" <michal.simek@....com>
Subject: RE: [LINUX PATCH v2 1/3] clocksource: timer-cadence-ttc: Do not probe
 TTC device configured as PWM

Hi Krzysztof,

> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Sent: Wednesday, November 15, 2023 5:41 PM
> To: Sayyed, Mubin <mubin.sayyed@....com>
> Cc: linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> devicetree@...r.kernel.org; linux-pwm@...r.kernel.org; git (AMD-Xilinx)
> <git@....com>; mubin10@...il.com; krzysztof.kozlowski+dt@...aro.org;
> u.kleine-koenig@...gutronix.de; thierry.reding@...il.com;
> robh+dt@...nel.org; conor+dt@...nel.org; tglx@...utronix.de;
> daniel.lezcano@...aro.org; Simek, Michal <michal.simek@....com>
> Subject: Re: [LINUX PATCH v2 1/3] clocksource: timer-cadence-ttc: Do not probe
> TTC device configured as PWM
> 
> On 15/11/2023 06:55, Sayyed, Mubin wrote:
> >>> +	/*
> >>> +	 * If pwm-cells property is present in TTC node,
> >>> +	 * it would be treated as PWM device.
> >>> +	 */
> >>> +	if (of_property_read_bool(timer, "#pwm-cells"))
> >>> +		return -ENODEV;
> >>
> >> You will introduce dmesg errors, so regressions.
> >>
> > [Mubin]: I will change it to "return 0" to avoid dmesg errors.
> 
> No, because solution is wrong.
> 
> >
> >> This does not look right. What you want is to bind one device driver
> >> and choose different functionality based on properties.
> > [Mubin]:  I am doing it based on earlier discussion related to AXI Timer PWM
> driver.  It was suggested to use #pwm-cells property for identifying role of
> device(PWM/clocksource) https://lore.kernel.org/linux-
> devicetree/20210513021631.GA878860@...h.at.kernel.org/.
> 
> You are mixing bindings with driver. I said here about driver and yes - you must
> use pwm-cells to differentiate that. It's obvious.
> 
> So again, one driver binding.
[Mubin]: I will explore whether mfd framework can be used to handle this.

Thanks,
Mubin
> 
> Wrap your emails to mailing list discussion style.
> 
> Best regards,
> Krzysztof