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.
Signed-off-by: Thierry Reding treding@nvidia.com --- 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");