linux-kernel - [PATCH v4 1/2] drm/simpledrm: Allow physical width and height configuration via panel node

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Message-Id: <20230126182435.70544-2-rayyan@ansari.sh>
Date:   Thu, 26 Jan 2023 18:24:34 +0000
From:   Rayyan Ansari <rayyan@...ari.sh>
To:     dri-devel@...ts.freedesktop.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht, asahi@...ts.linux.dev,
        janne@...nau.net, Rayyan Ansari <rayyan@...ari.sh>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>, devicetree@...r.kernel.org,
        Hans de Goede <hdegoede@...hat.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: [PATCH v4 1/2] drm/simpledrm: Allow physical width and height configuration via panel node

Parse the width-mm and height-mm devicetree properties of the panel node,
and use this to set the DRM Display Mode instead of calculating it
based on a hardcoded DPI.

Signed-off-by: Rayyan Ansari <rayyan@...ari.sh>
---
 drivers/gpu/drm/tiny/simpledrm.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index 162eb44dcba8..f8b18441cfcb 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -599,16 +599,12 @@ static const struct drm_mode_config_funcs simpledrm_mode_config_funcs = {
  */
 
 static struct drm_display_mode simpledrm_mode(unsigned int width,
-					      unsigned int height)
+					      unsigned int height,
+					      unsigned int width_mm,
+					      unsigned int height_mm)
 {
-	/*
-	 * Assume a monitor resolution of 96 dpi to
-	 * get a somewhat reasonable screen size.
-	 */
 	const struct drm_display_mode mode = {
-		DRM_MODE_INIT(60, width, height,
-			      DRM_MODE_RES_MM(width, 96ul),
-			      DRM_MODE_RES_MM(height, 96ul))
+		DRM_MODE_INIT(60, width, height, width_mm, height_mm)
 	};
 
 	return mode;
@@ -622,6 +618,8 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
 	struct simpledrm_device *sdev;
 	struct drm_device *dev;
 	int width, height, stride;
+	int width_mm = 0, height_mm = 0;
+	struct device_node *panel_node;
 	const struct drm_format_info *format;
 	struct resource *res, *mem;
 	void __iomem *screen_base;
@@ -676,6 +674,13 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
 		format = simplefb_get_format_of(dev, of_node);
 		if (IS_ERR(format))
 			return ERR_CAST(format);
+
+		panel_node = of_parse_phandle(of_node, "panel", 0);
+		if (panel_node) {
+			simplefb_read_u32_of(dev, panel_node, "width-mm", &width_mm);
+			simplefb_read_u32_of(dev, panel_node, "height-mm", &height_mm);
+			of_node_put(panel_node);
+		}
 	} else {
 		drm_err(dev, "no simplefb configuration found\n");
 		return ERR_PTR(-ENODEV);
@@ -686,7 +691,16 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
 			return ERR_PTR(-EINVAL);
 	}
 
-	sdev->mode = simpledrm_mode(width, height);
+	/*
+	 * Assume a monitor resolution of 96 dpi if physical dimensions
+	 * are not specified to get a somewhat reasonable screen size.
+	 */
+	if (!width_mm)
+		width_mm = DRM_MODE_RES_MM(width, 96ul);
+	if (!height_mm)
+		height_mm = DRM_MODE_RES_MM(height, 96ul);
+
+	sdev->mode = simpledrm_mode(width, height, width_mm, height_mm);
 	sdev->format = format;
 	sdev->pitch = stride;
 
-- 
2.39.1