linux-kernel - Re: [PATCH v3] intel/pinctrl: check REVID register value for device presence

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Message-ID: <YFyH9Fk5d+289/f/@smile.fi.intel.com>
Date:   Thu, 25 Mar 2021 14:54:12 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Roger Pau Monne <roger.pau@...rix.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andy@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org
Subject: Re: [PATCH v3] intel/pinctrl: check REVID register value for device
 presence

On Thu, Mar 25, 2021 at 10:09:47AM +0100, Roger Pau Monne wrote:
> Use the value read from the REVID register in order to check for the
> presence of the device. A read of all ones is treated as if the device
> is not present, and hence probing is ended.
> 
> This fixes an issue when running as a Xen PVH dom0, where the ACPI
> DSDT table is provided unmodified to dom0 and hence contains the
> pinctrl devices, but the MMIO region(s) containing the device
> registers might not be mapped in the guest physical memory map if such
> region(s) are not exposed on a PCI device BAR or marked as reserved in
> the host memory map.

Applied for fixes, thanks!

> 91d898e51e60 ('pinctrl: intel: Convert capability list to features')
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
> ---
> Changes since v2:
>  - Return ENODEV.
>  - Adjust code comment.
> 
> Changes since v1:
>  - New in this version.
> ---
> Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Cc: Andy Shevchenko <andy@...nel.org>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: linux-gpio@...r.kernel.org
> ---
>  drivers/pinctrl/intel/pinctrl-intel.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/intel/pinctrl-intel.c b/drivers/pinctrl/intel/pinctrl-intel.c
> index 8085782cd8f9..9fc5bba514ea 100644
> --- a/drivers/pinctrl/intel/pinctrl-intel.c
> +++ b/drivers/pinctrl/intel/pinctrl-intel.c
> @@ -1491,8 +1491,13 @@ static int intel_pinctrl_probe(struct platform_device *pdev,
>  		if (IS_ERR(regs))
>  			return PTR_ERR(regs);
>  
> -		/* Determine community features based on the revision */
> +		/*
> +		 * Determine community features based on the revision.
> +		 * A value of all ones means the device is not present.
> +		 */
>  		value = readl(regs + REVID);
> +		if (value == ~0u)
> +			return -ENODEV;
>  		if (((value & REVID_MASK) >> REVID_SHIFT) >= 0x94) {
>  			community->features |= PINCTRL_FEATURE_DEBOUNCE;
>  			community->features |= PINCTRL_FEATURE_1K_PD;
> -- 
> 2.30.1
> 

-- 
With Best Regards,
Andy Shevchenko