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

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Date:   Thu, 25 Jan 2018 17:13:58 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     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>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-gpio@...r.kernel.org,
        Grant Likely <grant.likely@...retlab.ca>,
        devicetree@...r.kernel.org
Subject: [PATCH v2 1/3] dt-bindings: pinctrl: Add a reserved-gpio-ranges property

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>
---
 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