linux-kernel - Re: [PATCH v2 1/3] dt-bindings: pinctrl: Add a reserved-gpio-ranges property

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Message-ID: <20180223163714.GM93895@bjorns-mbp-2.lan>
Date:   Fri, 23 Feb 2018 08:37:14 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <sboyd@...eaurora.org>, Rob Herring <robh@...nel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Timur Tabi <timur@...eaurora.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org,
        Grant Likely <grant.likely@...retlab.ca>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: pinctrl: Add a reserved-gpio-ranges
 property

On Thu 25 Jan 17:13 PST 2018, Stephen Boyd wrote:

+ Rob

> Some qcom platforms make some GPIOs or pins unavailable for use
> by non-secure operating systems, and thus reading or writing the
> registers for those pins will cause access control issues.
> Introduce a DT property to describe the set of GPIOs that are
> available for use so that higher level OSes are able to know what
> pins to avoid reading/writing.
> 
> Cc: Grant Likely <grant.likely@...retlab.ca>
> Cc: <devicetree@...r.kernel.org>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>

Acked-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> ---
>  Documentation/devicetree/bindings/gpio/gpio.txt | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
> index b5de08e3b1a2..c22b56680fc8 100644
> --- a/Documentation/devicetree/bindings/gpio/gpio.txt
> +++ b/Documentation/devicetree/bindings/gpio/gpio.txt
> @@ -151,9 +151,9 @@ in a lot of designs, some using all 32 bits, some using 18 and some using
>  first 18 GPIOs, at local offset 0 .. 17, are in use.
>  
>  If these GPIOs do not happen to be the first N GPIOs at offset 0...N-1, an
> -additional bitmask is needed to specify which GPIOs are actually in use,
> -and which are dummies. The bindings for this case has not yet been
> -specified, but should be specified if/when such hardware appears.
> +additional set of tuples is needed to specify which GPIOs are unusable, with
> +the reserved-gpio-ranges binding. This property indicates the start and size
> +of the GPIOs that can't be used.
>  
>  Optionally, a GPIO controller may have a "gpio-line-names" property. This is
>  an array of strings defining the names of the GPIO lines going out of the
> @@ -178,6 +178,7 @@ gpio-controller@...00000 {
>  	gpio-controller;
>  	#gpio-cells = <2>;
>  	ngpios = <18>;
> +	reserved-gpio-ranges = <0 4>, <12 2>;
>  	gpio-line-names = "MMC-CD", "MMC-WP", "VDD eth", "RST eth", "LED R",
>  		"LED G", "LED B", "Col A", "Col B", "Col C", "Col D",
>  		"Row A", "Row B", "Row C", "Row D", "NMI button",
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>