fbdev: ssd1307fb: Make reset gpio devicetree property optional

Make reset gpio devicetree property optional. Depending on the board
designing there may not be a dedicated gpio for resetting the
display. Without a proper reset there may be some junk in the display
memory at probe time, so in such a case the display memory is cleared
before turning it on. The devicetree binding document is also updated.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Benoît Cousson <bcousson@baylibre.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

2 files changed, 15 insertions, 8 deletions

diff --git a/Documentation/devicetree/bindings/display/ssd1307fb.txt b/Documentation/devicetree/bindings/display/ssd1307fb.txt
index 4aee67fdf2cf..6617df68d8b8 100644
--- a/Documentation/devicetree/bindings/display/ssd1307fb.txt
+++ b/Documentation/devicetree/bindings/display/ssd1307fb.txt
@@ -8,14 +8,14 @@ Required properties:
          0x3c or 0x3d
   - pwm: Should contain the pwm to use according to the OF device tree PWM
          specification [0]. Only required for the ssd1307.
-  - reset-gpios: Should contain the GPIO used to reset the OLED display. See
-                 Documentation/devicetree/bindings/gpio/gpio.txt for details.
   - solomon,height: Height in pixel of the screen driven by the controller
   - solomon,width: Width in pixel of the screen driven by the controller
   - solomon,page-offset: Offset of pages (band of 8 pixels) that the screen is
     mapped to.
 
 Optional properties:
+  - reset-gpios: The GPIO used to reset the OLED display, if available. See
+                 Documentation/devicetree/bindings/gpio/gpio.txt for details.
   - solomon,segment-no-remap: Display needs normal (non-inverted) data column
                               to segment mapping
   - solomon,com-seq: Display uses sequential COM pin configuration
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 8ffaaeeb2f84..89372af7bc5b 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -439,6 +439,10 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
         if (ret < 0)
                 return ret;
 
+        /* Clear the screen if we could not give reset at probe time */
+        if (!par->reset)
+                ssd1307fb_update_display(par);
+
         /* Turn on the display */
         ret = ssd1307fb_write_cmd(par->client, SSD1307FB_DISPLAY_ON);
         if (ret < 0)
@@ -561,7 +565,8 @@ static int ssd1307fb_probe(struct i2c_client *client,
 
         par->device_info = of_device_get_match_data(&client->dev);
 
-        par->reset = devm_gpiod_get(&client->dev, "reset", GPIOD_OUT_LOW);
+        par->reset = devm_gpiod_get_optional(&client->dev, "reset",
+                                             GPIOD_OUT_LOW);
         if (IS_ERR(par->reset)) {
                 dev_err(&client->dev, "failed to get reset gpio: %ld\n",
                         PTR_ERR(par->reset));
@@ -645,11 +650,13 @@ static int ssd1307fb_probe(struct i2c_client *client,
 
         i2c_set_clientdata(client, info);
 
-        /* Reset the screen */
-        gpiod_set_value(par->reset, 0);
-        udelay(4);
-        gpiod_set_value(par->reset, 1);
-        udelay(4);
+        if (par->reset) {
+                /* Reset the screen */
+                gpiod_set_value(par->reset, 0);
+                udelay(4);
+                gpiod_set_value(par->reset, 1);
+                udelay(4);
+        }
 
         ret = ssd1307fb_init(par);
         if (ret)