linux-kernel - Re: [PATCH 3/3] i2c: i801: Do not add ICH_RES_IO

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Message-ID: <20200225143545.GM10400@smile.fi.intel.com>
Date:   Tue, 25 Feb 2020 16:35:45 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Martin Volf <martin.volf.42@...il.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        linux-i2c@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] i2c: i801: Do not add ICH_RES_IO_SMI if PMC device
 is not present

On Tue, Feb 25, 2020 at 03:38:02PM +0300, Mika Westerberg wrote:
> Martin noticed that nct6775 driver does not load properly on his system
> in v5.4+ kernels. The issue was bisected to commit b84398d6d7f9 ("i2c:
> i801: Use iTCO version 6 in Cannon Lake PCH and beyond") but it is
> likely not the culprit because the faulty code has been in the driver
> already since commit 9424693035a5 ("i2c: i801: Create iTCO device on
> newer Intel PCHs"). So more likely some commit that added PCI IDs of
> recent chipsets made the driver to create the iTCO_wdt device on Martins
> system.
> 
> The issue was debugged to be PCI configuration access to the PMC device
> that is not present. This returns all 1's when read and this caused the
> iTCO_wdt driver to accidentally request resourses used by nct6775.
> 
> Fix this by checking that the PMC device is there and only then populate
> the iTCO_wdt ICH_RES_IO_SMI resource. Since the resource is now optional
> the iTCO_wdt driver should continue to work on recent systems without it.

...

>  	return platform_device_register_resndata(&pci_dev->dev, "iTCO_wdt", -1,
> -					tco_res, 3, &spt_tco_platform_data,
> +					tco_res, nres + 1, &spt_tco_platform_data,
>  					sizeof(spt_tco_platform_data));

Perhaps use the same pattern as below, i.e.

	nres++;
	return ...(..., nres, ...);

?

...

>  	return platform_device_register_resndata(&pci_dev->dev, "iTCO_wdt", -1,
> -					tco_res, 2, &cnl_tco_platform_data,
> +					tco_res, nres, &cnl_tco_platform_data,
>  					sizeof(cnl_tco_platform_data));

Ditto.

...

> +	nres++;

-- 
With Best Regards,
Andy Shevchenko