linux-kernel - Re: [PATCH v4 4/7] pinctrl: wpcm450: elax return value check for IRQ get

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Message-ID: <ZGOwCSPH68DJN/NC@probook>
Date:   Tue, 16 May 2023 18:32:09 +0200
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Andreas Klinger <ak@...klinger.de>,
        Marcin Wojtas <mw@...ihalf.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Linus Walleij <linus.walleij@...aro.org>,
        Paul Cercueil <paul@...pouillou.net>,
        Wolfram Sang <wsa@...nel.org>,
        Akhil R <akhilrajeev@...dia.com>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        netdev@...r.kernel.org, openbmc@...ts.ozlabs.org,
        linux-gpio@...r.kernel.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH v4 4/7] pinctrl: wpcm450: elax return value check for IRQ
 get

Hello,

> [PATCH v4 4/7] pinctrl: wpcm450: elax return value check for IRQ get

Typo ("elax") in the subject line.

>
On Tue, May 16, 2023 at 10:13:14AM +0300, Matti Vaittinen wrote:
> fwnode_irq_get[_byname]() were changed to not return 0 anymore. The
> special error case where device-tree based IRQ mapping fails can't no
> longer be reliably detected from this return value. This yields a
> functional change in the driver where the mapping failure is treated as
> an error.
> 
> The mapping failure can occur for example when the device-tree IRQ
> information translation call-back(s) (xlate) fail, IRQ domain is not
> found, IRQ type conflicts, etc. In most cases this indicates an error in
> the device-tree and special handling is not really required.
> 
> One more thing to note is that ACPI APIs do not return zero for any
> failures so this special handling did only apply on device-tree based
> systems.
> 
> Drop the special (no error, just skip the IRQ) handling for DT mapping
> failures as these can no longer be separated from other errors at driver
> side.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> 
> ---
> 
> The special handling in this driver was added when fixing a problem
> where returning zero from fwnode_irq_get[_byname]() was treated as
> succes yielding zero being used as a valid IRQ by the driver.
> f4a31facfa80 ("pinctrl: wpcm450: Correct the fwnode_irq_get() return value check")
> The commit message does not mention if choosing not to abort the probe
> on device-tree mapping failure (as is done on other errors) was chosen
> because: a) Abort would have broken some existing setup. b) Because skipping
> an IRQ on failure is "the right thing to do", or c) because it sounded like
> a way to minimize risk of breaking something.
> 
> If the reason is a) - then I'd appreciate receiving some more
> information and a suggestion how to proceed (if possible). If the reason
> is b), then it might be best to just skip the IRQ instead of aborting
> the probe for all errors on IRQ getting. Finally, in case of c), well,
> by acking this change you will now accept the risk :)
> 
> The first patch of the series changes the fwnode_irq_get() so this depends
> on the first patch of the series and should not be applied alone.

Thanks for investigating this!

It's not a), because there are no existing setups that rely on broken
IRQs connected to this pinctrl/GPIO controller.

I suspect b) or c), but I'll let Andy give a more definite answer.

> ---
>  drivers/pinctrl/nuvoton/pinctrl-wpcm450.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/pinctrl/nuvoton/pinctrl-wpcm450.c b/drivers/pinctrl/nuvoton/pinctrl-wpcm450.c
> index 2d1c1652cfd9..f9326210b5eb 100644
> --- a/drivers/pinctrl/nuvoton/pinctrl-wpcm450.c
> +++ b/drivers/pinctrl/nuvoton/pinctrl-wpcm450.c
> @@ -1106,8 +1106,6 @@ static int wpcm450_gpio_register(struct platform_device *pdev,
>  			irq = fwnode_irq_get(child, i);
>  			if (irq < 0)
>  				break;
> -			if (!irq)
> -				continue;
>  
>  			girq->parents[i] = irq;
>  			girq->num_parents++;

Anyway, this looks good to me.

Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@....net>

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