linux-kernel - [PATCH v2 4/4] ARM: mxs: cfa10036: Fixup OLED display reset polarity

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Date:   Thu, 20 Dec 2018 12:13:57 +0000
From:   Vokáč Michal <Michal.Vokac@...ft.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
CC:     Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Vokáč Michal <Michal.Vokac@...ft.com>
Subject: [PATCH v2 4/4] ARM: mxs: cfa10036: Fixup OLED display reset polarity

There was a bug in reset signal generation in ssd1307fb OLED driver.
The display needs an active-low reset signal but the driver produced
the correct sequence only if the GPIO used for reset was specified as
GPIO_ACTIVE_HIGH.

Now as the OLED driver is fixed it is also necessarry to implement
a fixup for all current users of the old DT ABI. There is only one
in-tree user and that is the Crystalfontz CFA-10036 board. In case
this board is booting and GPIO_ACTIVE_HIGH is used for reset we
override it to GPIO_ACTIVE_LOW.

Reviewed-by: Rob Herring <robh@...nel.org>
Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
---
Changes from v1:
 - Add R-by from Rob
 - Use of_property_read_variable_u32_array to read the GPIO specifier
   array instead of reading it manualy in for cycle. (Rob)

 arch/arm/mach-mxs/mach-mxs.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/arch/arm/mach-mxs/mach-mxs.c b/arch/arm/mach-mxs/mach-mxs.c
index 1c6062d..50038d6 100644
--- a/arch/arm/mach-mxs/mach-mxs.c
+++ b/arch/arm/mach-mxs/mach-mxs.c
@@ -21,6 +21,7 @@
 #include <linux/reboot.h>
 #include <linux/micrel_phy.h>
 #include <linux/of_address.h>
+#include <linux/of_gpio.h>
 #include <linux/of_platform.h>
 #include <linux/phy.h>
 #include <linux/pinctrl/consumer.h>
@@ -268,9 +269,52 @@ static void __init apx4devkit_init(void)
 					   apx4devkit_phy_fixup);
 }
 
+#define OLED_RESET_GPIO_LEN	3
+#define OLED_RESET_GPIO_SIZE	(OLED_RESET_GPIO_LEN * sizeof(u32))
+
+static void __init crystalfontz_oled_reset_fixup(void)
+{
+	struct property *newgpio;
+	struct device_node *np;
+	u32 *gpiospec;
+	int ret;
+
+	np = of_find_compatible_node(NULL, NULL, "solomon,ssd1306fb-i2c");
+	if (!np)
+		return;
+
+	newgpio = kzalloc(sizeof(*newgpio) + OLED_RESET_GPIO_SIZE, GFP_KERNEL);
+	if (!newgpio)
+		return;
+
+	newgpio->value = newgpio + 1;
+	newgpio->length = OLED_RESET_GPIO_SIZE;
+	newgpio->name = kstrdup("reset-gpios", GFP_KERNEL);
+	if (!newgpio->name) {
+		kfree(newgpio);
+		return;
+	}
+
+	gpiospec = newgpio->value;
+	ret = of_property_read_variable_u32_array(np, "reset-gpios", gpiospec,
+						  OLED_RESET_GPIO_LEN, 0);
+
+	if (ret < 0) {
+		kfree(newgpio);
+		return;
+	}
+
+	if (!(gpiospec[2] & OF_GPIO_ACTIVE_LOW)) {
+		gpiospec[2] |= OF_GPIO_ACTIVE_LOW;
+		cpu_to_be32_array(gpiospec, gpiospec, OLED_RESET_GPIO_LEN);
+		of_update_property(np, newgpio);
+	}
+}
+
 static void __init crystalfontz_init(void)
 {
 	update_fec_mac_prop(OUI_CRYSTALFONTZ);
+	crystalfontz_oled_reset_fixup();
 }
 
 static void __init duckbill_init(void)
-- 
2.1.4