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

From: Rayyan Ansari
Date: Thu Jan 26 2023 - 13:25:07 EST


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@xxxxxxxxx>
---
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