[PATCH RESEND v2 0/4] Fix ssd1307fb OLED driver reset

[PATCH RESEND v2 0/4] Fix ssd1307fb OLED driver reset

[Michal Vokáč]

Hi all,

this is my third attempt to fix the ssd1307fb OLED driver reset. In the
second attempt [1] Rob suggested to take different aproach. That is to
apply what was originaly part of the first round and eventually merged
but reverted later on [2][3].

The last patch in this series is a fixup for the single user (in-tree)
that uses this OLED. Rob suggested the fixup may actually be applied
only after someone complains their display broke.

And a comment from Alexandre regarding the status of the Crystalfontz
platform:

On 20.12.2018 13:35, Alexandre Belloni wrote:
> Honestly, the platform has been discontinued and I don't really think
> it is worth having that fixup in the tree forever.

Thank you,
Michal

[1] https://patchwork.kernel.org/patch/10665597/#22327227
[2] https://patchwork.kernel.org/patch/10617729/
[3] https://patchwork.kernel.org/patch/10617731/#22257175

Michal Vokáč (4):
  dt-bindings: display: ssd1307fb: Remove reset-active-low from examples
  video: ssd1307fb: Do not hard code active-low reset sequence
  ARM: dts: imx28-cfa10036: Fix the reset gpio signal polarity
  ARM: mxs: cfa10036: Fixup OLED display reset polarity

 .../devicetree/bindings/display/ssd1307fb.txt      |  2 -
 arch/arm/boot/dts/imx28-cfa10036.dts               |  3 +-
 arch/arm/mach-mxs/mach-mxs.c                       | 44 ++++++++++++++++++++++
 drivers/video/fbdev/ssd1307fb.c                    |  4 +-
 4 files changed, 48 insertions(+), 5 deletions(-)

-- 
2.1.4

[PATCH RESEND v2 1/4] dt-bindings: display: ssd1307fb: Remove reset-active-low from examples

[Michal Vokáč]

The reset-active-low property has been removed brom the binding a while
ago. So remove it from the examples as well.

Fixes: 519b4db ("fbdev: ssd1307fb: Remove reset-active-low from the DT binding document")
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
Changes in v2 resend:
 - Add R-by from Alexandre.

Changes from v1:
 - Add R-by from Rob

 Documentation/devicetree/bindings/display/ssd1307fb.txt | 2 --
 1 file changed, 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/ssd1307fb.txt b/Documentation/devicetree/bindings/display/ssd1307fb.txt
index 209d931..b67f8ca 100644
--- a/Documentation/devicetree/bindings/display/ssd1307fb.txt
+++ b/Documentation/devicetree/bindings/display/ssd1307fb.txt
@@ -36,7 +36,6 @@ ssd1307: oled@3c {
         reg = <0x3c>;
         pwms = <&pwm 4 3000>;
         reset-gpios = <&gpio2 7>;
-        reset-active-low;
 };
 
 ssd1306: oled@3c {
@@ -44,7 +43,6 @@ ssd1306: oled@3c {
         reg = <0x3c>;
         pwms = <&pwm 4 3000>;
         reset-gpios = <&gpio2 7>;
-        reset-active-low;
         solomon,com-lrremap;
         solomon,com-invdir;
         solomon,com-offset = <32>;
-- 
2.1.4

[PATCH RESEND v2 2/4] video: ssd1307fb: Do not hard code active-low reset sequence

[Michal Vokáč]

The SSD130x OLED display reset signal is active low. Now the reset
sequence is implemented in such a way that users are forced to
define reset-gpios as GPIO_ACTIVE_HIGH in DT to make the reset work.

Do not hard code the active-low sequence into the driver but instead
allow the user to specify the gpio as GPIO_ACTIVE_LOW to reflect
the real world.

Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
Changes in v2 resend:
 - Add R-by from Alexandre.

Changes from v1:
 - Add R-by from Rob

 drivers/video/fbdev/ssd1307fb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 4061a20..3b361bc 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -667,10 +667,10 @@ static int ssd1307fb_probe(struct i2c_client *client,
 
 	if (par->reset) {
 		/* Reset the screen */
-		gpiod_set_value_cansleep(par->reset, 0);
-		udelay(4);
 		gpiod_set_value_cansleep(par->reset, 1);
 		udelay(4);
+		gpiod_set_value_cansleep(par->reset, 0);
+		udelay(4);
 	}
 
 	if (par->vbat_reg) {
-- 
2.1.4

[PATCH RESEND v2 3/4] ARM: dts: imx28-cfa10036: Fix the reset gpio signal polarity

[Michal Vokáč]

The reset signal of the SSD1306 OLED display is actually active-low.
Adapt the DT to reflect the real world.

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
Changes in v2 resend:
 - Add Acked-by from Alexandre.

Changes from v1:
 - Add R-by from Rob

 arch/arm/boot/dts/imx28-cfa10036.dts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/imx28-cfa10036.dts b/arch/arm/boot/dts/imx28-cfa10036.dts
index d3e3622..de48b58 100644
--- a/arch/arm/boot/dts/imx28-cfa10036.dts
+++ b/arch/arm/boot/dts/imx28-cfa10036.dts
@@ -11,6 +11,7 @@
 
 /dts-v1/;
 #include "imx28.dtsi"
+#include <dt-bindings/gpio/gpio.h>
 
 / {
 	model = "Crystalfontz CFA-10036 Board";
@@ -96,7 +97,7 @@
 					pinctrl-names = "default";
 					pinctrl-0 = <&ssd1306_cfa10036>;
 					reg = <0x3c>;
-					reset-gpios = <&gpio2 7 0>;
+					reset-gpios = <&gpio2 7 GPIO_ACTIVE_LOW>;
 					solomon,height = <32>;
 					solomon,width = <128>;
 					solomon,page-offset = <0>;
-- 
2.1.4

[PATCH RESEND v2 4/4] ARM: mxs: cfa10036: Fixup OLED display reset polarity

[Michal Vokáč]

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

Re: [PATCH혻RESEND v2 0/4] Fix ssd1307fb OLED driver reset

[Bartlomiej Zolnierkiewicz]

On 01/28/2019 12:52 PM, Michal Vokáč wrote:
> Hi all,
> 
> this is my third attempt to fix the ssd1307fb OLED driver reset. In the
> second attempt [1] Rob suggested to take different aproach. That is to
> apply what was originaly part of the first round and eventually merged
> but reverted later on [2][3].
> 
> The last patch in this series is a fixup for the single user (in-tree)
> that uses this OLED. Rob suggested the fixup may actually be applied
> only after someone complains their display broke.
> 
> And a comment from Alexandre regarding the status of the Crystalfontz
> platform:
> 
> On 20.12.2018 13:35, Alexandre Belloni wrote:
>> Honestly, the platform has been discontinued and I don't really think
>> it is worth having that fixup in the tree forever.

Patches #1-3 queued for v5.1, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics