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Subject[PATCH v2 4/4] ARM: mxs: cfa10036: Fixup OLED display reset polarity
Date
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@kernel.org>
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.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
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