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Subject: Re: [PATCH v2 3/3] i2c: i801: Do not add ICH_RES_IO_SMI for the
 iTCO_wdt device
To:     Mika Westerberg <mika.westerberg@linux.intel.com>,
        Jean Delvare <jdelvare@suse.com>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Wolfram Sang <wsa@the-dreams.de>
Cc:     Martin Volf <martin.volf.42@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Jarkko Nikula <jarkko.nikula@linux.intel.com>,
        linux-i2c@vger.kernel.org, linux-hwmon@vger.kernel.org,
        linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200226132122.62805-1-mika.westerberg@linux.intel.com>
 <20200226132122.62805-4-mika.westerberg@linux.intel.com>
From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <f8549db6-de8a-2205-5cef-f0cb457a21f1@roeck-us.net>
Date:   Wed, 26 Feb 2020 05:31:31 -0800
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On 2/26/20 5:21 AM, 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.
> 
> It turns out that the SMI resource is only required for some ancient
> systems, not the ones supported by this driver. For this reason do not
> populate the SMI resource at all and drop all the related code. The
> driver now always populates the main I/O resource and only in case of SPT
> (Intel Sunrisepoint) compatible devices it adds another resource for the
> NO_REBOOT bit. These two resources are of different types so
> platform_get_resource() used by the iTCO_wdt driver continues to find
> the both resources at index 0.
> 
> Link: https://lore.kernel.org/linux-hwmon/CAM1AHpQ4196tyD=HhBu-2donSsuogabkfP03v1YF26Q7_BgvgA@mail.gmail.com/
> Fixes: 9424693035a5 ("i2c: i801: Create iTCO device on newer Intel PCHs")
> Reported-by: Martin Volf <martin.volf.42@gmail.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/i2c/busses/i2c-i801.c | 45 ++++++++++-------------------------
>  1 file changed, 12 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index ca4f096fef74..a9c03f5c3482 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -132,11 +132,6 @@
>  #define TCOBASE		0x050
>  #define TCOCTL		0x054
>  
> -#define ACPIBASE		0x040
> -#define ACPIBASE_SMI_OFF	0x030
> -#define ACPICTRL		0x044
> -#define ACPICTRL_EN		0x080
> -
>  #define SBREG_BAR		0x10
>  #define SBREG_SMBCTRL		0xc6000c
>  #define SBREG_SMBCTRL_DNV	0xcf000c
> @@ -1553,7 +1548,7 @@ i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
>  		pci_bus_write_config_byte(pci_dev->bus, devfn, 0xe1, hidden);
>  	spin_unlock(&p2sb_spinlock);
>  
> -	res = &tco_res[ICH_RES_MEM_OFF];
> +	res = &tco_res[1];
>  	if (pci_dev->device == PCI_DEVICE_ID_INTEL_DNV_SMBUS)
>  		res->start = (resource_size_t)base64_addr + SBREG_SMBCTRL_DNV;
>  	else
> @@ -1563,7 +1558,7 @@ i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
>  	res->flags = IORESOURCE_MEM;
>  
>  	return platform_device_register_resndata(&pci_dev->dev, "iTCO_wdt", -1,
> -					tco_res, 3, &spt_tco_platform_data,
> +					tco_res, 2, &spt_tco_platform_data,
>  					sizeof(spt_tco_platform_data));
>  }
>  
> @@ -1576,17 +1571,16 @@ static struct platform_device *
>  i801_add_tco_cnl(struct i801_priv *priv, struct pci_dev *pci_dev,
>  		 struct resource *tco_res)
>  {
> -	return platform_device_register_resndata(&pci_dev->dev, "iTCO_wdt", -1,
> -					tco_res, 2, &cnl_tco_platform_data,
> -					sizeof(cnl_tco_platform_data));
> +	return platform_device_register_resndata(&pci_dev->dev,
> +			"iTCO_wdt", -1, tco_res, 1, &cnl_tco_platform_data,
> +			sizeof(cnl_tco_platform_data));
>  }
>  
>  static void i801_add_tco(struct i801_priv *priv)
>  {
> -	u32 base_addr, tco_base, tco_ctl, ctrl_val;
>  	struct pci_dev *pci_dev = priv->pci_dev;
> -	struct resource tco_res[3], *res;
> -	unsigned int devfn;
> +	struct resource tco_res[2], *res;
> +	u32 tco_base, tco_ctl;
>  
>  	/* If we have ACPI based watchdog use that instead */
>  	if (acpi_has_watchdog())
> @@ -1601,30 +1595,15 @@ static void i801_add_tco(struct i801_priv *priv)
>  		return;
>  
>  	memset(tco_res, 0, sizeof(tco_res));
> -
> -	res = &tco_res[ICH_RES_IO_TCO];
> -	res->start = tco_base & ~1;
> -	res->end = res->start + 32 - 1;
> -	res->flags = IORESOURCE_IO;
> -
>  	/*
> -	 * Power Management registers.
> +	 * Always populate the main iTCO IO resource here. The second entry
> +	 * for NO_REBOOT MMIO is filled by the SPT specific function.
>  	 */
> -	devfn = PCI_DEVFN(PCI_SLOT(pci_dev->devfn), 2);
> -	pci_bus_read_config_dword(pci_dev->bus, devfn, ACPIBASE, &base_addr);
> -
> -	res = &tco_res[ICH_RES_IO_SMI];
> -	res->start = (base_addr & ~1) + ACPIBASE_SMI_OFF;
> -	res->end = res->start + 3;
> +	res = &tco_res[0];
> +	res->start = tco_base & ~1;
> +	res->end = res->start + 32 - 1;
>  	res->flags = IORESOURCE_IO;
>  
> -	/*
> -	 * Enable the ACPI I/O space.
> -	 */
> -	pci_bus_read_config_dword(pci_dev->bus, devfn, ACPICTRL, &ctrl_val);
> -	ctrl_val |= ACPICTRL_EN;
> -	pci_bus_write_config_dword(pci_dev->bus, devfn, ACPICTRL, ctrl_val);
> -
>  	if (priv->features & FEATURE_TCO_CNL)
>  		priv->tco_pdev = i801_add_tco_cnl(priv, pci_dev, tco_res);
>  	else
>