drm/panel: mantix panel reset fixes

Posting as RFC since I'm not sure how to handle the bindings, please see below.

The first patch in this series fixes dereferencing a NULL mode in the error path. The second one extends the resets to not only reset RESX but also TP_RSTN since otherwise the display will stay completely blank. I didn't spot that before initial submission since the reset line was bound to the touch controller and although that failed to probe it came far enough to deassert the reset line (at an arbitrary point in time during boot) and hence we got a picture. Since touch and panel are on the same IC they're not completely independent and i might have to turn the whole thing into an MFD at some point but this series gets the panel to a reliably working state on boot and on fb blank/unblank.

Since the reset-gpios are active low we can deassert in prepare and assert in unprepare simplifying the code making sure lines are kept low when the panel is off.

As for the bindings it seems I can't override the maxItems of reset-gpios since that is already set in bindings/display/panel/panel-common.yaml to maxItems:
1. Is there a way to do that instead of side stepping the issue and using a different name or using enable-gpios for one of them or forcing everyone else to set maxItems: 1`?

The binding were not part of a stable kernel so I hope it's okay to not worry about backward compatibility.

Guido Günther (3):
drm/panel: mantix: Don't dereference NULL mode drm/panel: mantix: Fix panel reset
dt-binding: display: Require two rests on mantix panel

 .../display/panel/mantix,mlaf057we51-x.yaml   |  7 +++-
 .../gpu/drm/panel/panel-mantix-mlaf057we51.c  | 39 ++++++++++++-------
 2 files changed, 30 insertions(+), 16 deletions(-)

2.26.2

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Don't dereference mode which was just NULL checked.

---
 drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 3482e28e30fc..4a7fbf64bb7a 100644
@@ -204,7 +204,7 @@ static int mantix_get_modes(struct drm_panel *panel,
 	if (!mode) {
 		dev_err(ctx->dev, "Failed to add mode %ux%u@%u\n",
 			default_mode.hdisplay, default_mode.vdisplay,
-			drm_mode_vrefresh(mode));
+			drm_mode_vrefresh(&default_mode));
 		return -ENOMEM;
 	}
 

2.26.2

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The mantix panel needs two reset lines (RESX and TP_RSTN) deasserted to output an image. Only deasserting RESX is not enough and the display will stay blank. Deassert in prepare() and assert in unprepare() to keep device held in reset when off.

---
 .../gpu/drm/panel/panel-mantix-mlaf057we51.c  | 37 ++++++++++++-------
 1 file changed, 24 insertions(+), 13 deletions(-)

index 4a7fbf64bb7a..29d28c63bb72 100644
@@ -23,10 +23,13 @@
 #define MANTIX_CMD_OTP_STOP_RELOAD_MIPI 0x41
 #define MANTIX_CMD_INT_CANCEL           0x4C
 
+#define MANTIX_NUM_RESETS 2
+
 struct mantix {
 	struct device *dev;
 	struct drm_panel panel;
-	struct gpio_desc *reset_gpio;
+	/* RESX and TP_RSTN */
+	struct gpio_descs *reset_gpios;
 
 	struct regulator *avdd;
 	struct regulator *avee;

@@ -122,8 +125,13 @@ static int mantix_disable(struct drm_panel *panel)
 
 static int mantix_unprepare(struct drm_panel *panel)
 {
+	DECLARE_BITMAP(asserted_values, BITS_PER_TYPE(1));
 	struct mantix *ctx = panel_to_mantix(panel);
 
+	gpiod_set_array_value_cansleep(ctx->reset_gpios->ndescs,
+				       ctx->reset_gpios->desc,
+				       ctx->reset_gpios->info, asserted_values);
+
 	regulator_disable(ctx->avee);
 	regulator_disable(ctx->avdd);
 	/* T11 */

@@ -137,6 +145,7 @@ static int mantix_unprepare(struct drm_panel *panel)
 
 static int mantix_prepare(struct drm_panel *panel)
 {
+	DECLARE_BITMAP(deasserted_values, BITS_PER_TYPE(0));
 	struct mantix *ctx = panel_to_mantix(panel);
 	int ret;
 

@@ -165,14 +174,11 @@ static int mantix_prepare(struct drm_panel *panel)
 		return ret;
 	}
 
-	/* T3+T5 */
-	usleep_range(10000, 12000);
-
-	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
-	usleep_range(5150, 7000);
-
-	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
-
+	/* T3 + T4 + time for voltage to become stable: */
+	usleep_range(6000, 7000);
+	gpiod_set_array_value_cansleep(ctx->reset_gpios->ndescs,
+				       ctx->reset_gpios->desc,
+				       ctx->reset_gpios->info, deasserted_values);
 	/* T6 */
 	msleep(50);
 

@@ -236,10 +242,15 @@ static int mantix_probe(struct mipi_dsi_device *dsi)
 	if (!ctx)
 		return -ENOMEM;
 
-	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
-	if (IS_ERR(ctx->reset_gpio)) {
-		dev_err(dev, "cannot get reset gpio\n");
-		return PTR_ERR(ctx->reset_gpio);
+	ctx->reset_gpios = devm_gpiod_get_array(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ctx->reset_gpios)) {
+		dev_err(dev, "cannot get reset gpios\n");
+		return PTR_ERR(ctx->reset_gpios);
+	}
+
+	if (ctx->reset_gpios->ndescs != MANTIX_NUM_RESETS) {
+		dev_err(dev, "Need exactly %d reset-gpios\n", MANTIX_NUM_RESETS);
+		return -EINVAL;
 	}
 
 	mipi_dsi_set_drvdata(dsi, ctx);

2.26.2

We need to reset both for the panel to show an image.

---
 .../bindings/display/panel/mantix,mlaf057we51-x.yaml       | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

index 937323cc9aaa..ba5a18fac9f9 100644
@@ -35,7 +35,9 @@ properties:
   vddi-supply:
     description: 1.8V I/O voltage supply
 
-  reset-gpios: true
+  reset-gpios:
+    minItems: 2
+    maxItems: 2
 
   backlight: true
 

@@ -62,7 +64,8 @@ examples:
             avdd-supply = <&reg_avdd>;
             avee-supply = <&reg_avee>;
             vddi-supply = <&reg_1v8_p>;
-            reset-gpios = <&gpio1 29 GPIO_ACTIVE_LOW>;
+            reset-gpios = <&gpio1 29 GPIO_ACTIVE_LOW>,
+                          <&gpio1 24 GPIO_ACTIVE_LOW>;
             backlight = <&backlight>;
         };
     };

2.26.2

Hi Guido,

There is a typo in "resets" in the Subject line.
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Hi,

Fix queued for v2. Thanks!
-- Guido

Hi Guido.

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My understanding is that this will only override the defaults defined in panel-common.yaml. So everything else about the panel-common.yaml#/properties/reset-gpios definition remains valid and all this does is say that when this matched on "mantix,mlaf057we51-x", then the "reset-gpios" property is expected to contain two entries as opposed to the single entry that is expected by default.

Thierry

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Hi Thierry,

I thought so too but I get:

linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.example.dt.yaml: panel@0: reset-gpios: [[4294967295, 29, 1], [4294967295, 24, 1]] is too long
From schema: /.../linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml

It seems to bepossible to *extend* reset-gpios though because when i use an example like:

            reset-gpios = <&gpio1 29 GPIO_ACTIVE_LOW>,
                          <&gpio1 24 GPIO_ACTIVE_LOW>;

i correctly get

linux/linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.example.dt.yaml: panel@0: reset-gpios: [[4294967295, 29, 1]] is too short
From schema: /.../linux/Documentation/devicetree/bindings/display/panel/mantix,mlaf057we51-x.yaml

so the minItems: 2 is being picked up. This mens i can add properties but i can't overwrite the existing maxItems: 2 - that's why i was wondering how that is supposed to work (if properties should be overrideable from common files or not).
Cheers,
-- Guido

Yes.

You also need to define what each reset entry corresponds to as the assertion/deassertion order could be important. You might just do 2 properties with <pinname>-gpios.

Rob