The head number of a given display controller is fixed in hardware and
required to program outputs appropriately. Relying on the driver probe
order to determine this number will not work, since that could yield a
situation where the second head was probed first and would be assigned
head number 0 instead of 1.
By explicitly specifying the head number in the device tree, it is no
longer necessary to rely on these assumptions. As a fallback, if the
property isn't available, derive the head number from the display
controller node's position in the device tree. That's somewhat more
reliable than the previous default but not a proper solution.
Tested-by: Stephen Warren <swarren@xxxxxxxxxx>
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v2:
- if the nvidia,head property isn't present, find the position of the
display controller within the DT and derive the head number from it
.../bindings/gpu/nvidia,tegra20-host1x.txt | 3 ++
drivers/gpu/drm/tegra/dc.c | 41 ++++++++++++++++++++--
2 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/Documentation/devicetree/bindings/gpu/nvidia,tegra20-host1x.txt b/Documentation/devicetree/bindings/gpu/nvidia,tegra20-host1x.txt
index 9e9008f8fa32..efaeec8961b6 100644
--- a/Documentation/devicetree/bindings/gpu/nvidia,tegra20-host1x.txt
+++ b/Documentation/devicetree/bindings/gpu/nvidia,tegra20-host1x.txt
@@ -118,6 +118,9 @@ of the following host1x client modules:
See ../reset/reset.txt for details.
- reset-names: Must include the following entries:
- dc
+ - nvidia,head: The number of the display controller head. This is used to
+ setup the various types of output to receive video data from the given
+ head.
Each display controller node has a child node, named "rgb", that represents
the RGB output associated with the controller. It can take the following
diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 386f3b4b0094..9336006b475d 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -1100,8 +1100,6 @@ static int tegra_dc_init(struct host1x_client *client)
struct tegra_dc *dc = host1x_client_to_dc(client);
int err;
- dc->pipe = tegra->drm->mode_config.num_crtc;
-
drm_crtc_init(tegra->drm, &dc->base, &tegra_crtc_funcs);
drm_mode_crtc_set_gamma_size(&dc->base, 256);
drm_crtc_helper_add(&dc->base, &tegra_crtc_helper_funcs);
@@ -1187,6 +1185,41 @@ static const struct of_device_id tegra_dc_of_match[] = {
}
};
+static int tegra_dc_parse_dt(struct tegra_dc *dc)
+{
+ struct device_node *np;
+ u32 value = 0;
+ int err;
+
+ err = of_property_read_u32(dc->dev->of_node, "nvidia,head", &value);
+ if (err < 0) {
+ dev_err(dc->dev, "missing \"nvidia,head\" property\n");
+
+ /*
+ * If the nvidia,head property isn't present, try to find the
+ * correct head number by looking up the position of this
+ * display controller's node within the device tree. Assuming
+ * that the nodes are ordered properly in the DTS file and
+ * that the translation into a flattened device tree blob
+ * preserves that ordering this will actually yield the right
+ * head number.
+ *
+ * If those assumptions don't hold, this will still work for
+ * cases where only a single display controller is used.
+ */
+ for_each_matching_node(np, tegra_dc_of_match) {
+ if (np == dc->dev->of_node)
+ break;
+
+ value++;
+ }
+ }
+
+ dc->pipe = value;
+
+ return 0;
+}
+
static int tegra_dc_probe(struct platform_device *pdev)
{
const struct of_device_id *id;
@@ -1207,6 +1240,10 @@ static int tegra_dc_probe(struct platform_device *pdev)
dc->dev = &pdev->dev;
dc->soc = id->data;
+ err = tegra_dc_parse_dt(dc);
+ if (err < 0)
+ return err;
+
dc->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(dc->clk)) {
dev_err(&pdev->dev, "failed to get clock\n");
--
1.8.4.2
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