linux-kernel - [PATCH] gpio: of: Optimize quirk checks

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Date:   Fri, 29 Mar 2019 09:42:29 +0100
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH] gpio: of: Optimize quirk checks

Simple string comparisons are cheaper than DT lookups, as the latter
involve taking a spinlock and traversing properties.
Hence optimize quirk checks by postponing DT lookups after string
comparisons.

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
 drivers/gpio/gpiolib-of.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 6a3ec575a404ed9f..3a6bb53d89dfed32 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -86,9 +86,9 @@ static void of_gpio_flags_quirks(struct device_node *np,
 	if (IS_ENABLED(CONFIG_REGULATOR) &&
 	    (of_device_is_compatible(np, "regulator-fixed") ||
 	     of_device_is_compatible(np, "reg-fixed-voltage") ||
-	     (of_device_is_compatible(np, "regulator-gpio") &&
-	      !(strcmp(propname, "enable-gpio") &&
-	        strcmp(propname, "enable-gpios"))))) {
+	     (!(strcmp(propname, "enable-gpio") &&
+		strcmp(propname, "enable-gpios")) &&
+	      of_device_is_compatible(np, "regulator-gpio")))) {
 		/*
 		 * The regulator GPIO handles are specified such that the
 		 * presence or absence of "enable-active-high" solely controls
@@ -119,9 +119,8 @@ static void of_gpio_flags_quirks(struct device_node *np,
 	 * property named "cs-gpios" we need to inspect the child node
 	 * to determine if the flags should have inverted semantics.
 	 */
-	if (IS_ENABLED(CONFIG_SPI_MASTER) &&
-	    of_property_read_bool(np, "cs-gpios") &&
-	    !strcmp(propname, "cs-gpios")) {
+	if (IS_ENABLED(CONFIG_SPI_MASTER) && !strcmp(propname, "cs-gpios") &&
+	    of_property_read_bool(np, "cs-gpios")) {
 		struct device_node *child;
 		u32 cs;
 		int ret;
-- 
2.17.1